fac.ksu.edu.sa · 2018. 8. 9. · was due to retruded maxilla and relatively normal and/or...

SKELETO-DENTAL CHARACTERISTICS FEATURES

AMONG SAUDI FEMALE SCHOOL CHILDREN.

A CEPHALOMETRIC STUDY

THESIS

Submitted in partial fulfillment of the requirements for the

MASTER OF SCIENCE DEGREE IN DENTISTRY

(ORTHODONTICS)

BY

SAHAR FAISAL AL-BARAKATI, BDS

Department of Preventive Dental Sciences

King Saud University, College of Dentistry

1416H [1996]

SKELETO-DENTAL CHARACTERISTICS FEATURES

AMONG SAUDI FEMALE SCHOOL CHILDREN.

A CEPHALOMETRIC STUDY

THESIS by

SAHAR AL-BARAKATI

Thesis defended on July 3, 1996 and approved.

Supervisor

DR. MOHAMED BUKHARY

Examination Committee

DR. HAYDER HASHIM DR. RABAB FETEIH

DR. ERNEST GUILE PROF. J.O. ADENUBI

ABSTRACT

The skeleto-dental characteristic features of the different classes

were studied in 205 cephalometric radiographs of Saudi females school

children, representing the age range of 10 – 12 years. The sample was

selected from a pool of 5112 subjects in Jeddah City.

Two hypothesis were stated, tested and the results of the study

suggest accepting the hypothesis.

18 angular, 17 linear and 2 proportional variables were

investigated. Descriptive statistics and student t-test were used for the

data Descriptive statistics and student t-test were used for the data

analysis. The error of the method was calculated and found to be within

the acceptable range.

The distribution of the skeletal relationship revealed that 68.3%

of the sample showed class I relationship, 16.1% class II and 15.6%

class III.

The skeleto-dental characteristic features of class II and class III

were compared to class I of this Saudi sample. The result indicates

significant differences between the different classes.

Class II skeletal relationship was found to be due to maxillary

protrusion and retrusion of the mandible, whereas, class III relationship

was due to retruded maxilla and relatively normal and/or protruded

mandible.

The results also revealed that the upper incisors were retroclined

and the lower incisors were procline in class II skeletal relationship.

The opposite was observed in class III.

Besides, the results obtained for class I in the Saudi sample were

compared to the established mean for the North American Caucasians

and British. The Saudi female skeleton-dental characteristic feature

was found to be neared to the British sample than the North American

Caucasians. However, the dento-alveolar relationship variables showed

more protrusion of the upper and lower incisors (Bimaxillary

protrusion).

The results obtained can be of great value not only in

distinguishing the various skeleton-dental features in the different

skeletal classes among the Saudi females but also in the clinical

diagnosis and treatment planning.

Furthermore, the results of the study can also serve as base-line

for future investigations in Saudi Arabia.

6

TABLE OF CONTENTS

Abstract 4

Table of Contents 6

List of figures 11

List of tables 12

Dedication 19

Acknowledgements 20

1.0 Introduction 22

2.0 Review of Literature 25

2.1 Malocclusions and skeletal discrepancy 26

2.1.1 Normal occlusion 26

2.1.2 Malocclusion 26

2.1.3 Skeletal discrepancy 29

2.1.4 The role of genetic factors in the

production of malocclusion 32

2.1.5 The role of environment factors in

the production of malocclusion 33

2.2 The growth of the cranio-facial skeleton 36

2.2.1 Growth mechanism 36

2.2.1. a Cortical drift 36

2.2.1. b Displacement 37

2.2.1. c Remodeling 38

2.2.2 Growth of the midface 38

2.2.3 Maxillary growth 38

2.2.4 Mandibular growth 39

2.2.5 Intermaxillary relationship 41

2.2.6 Growth consideration 41

2.3 Racial variation 42

7

2.4 Cephalometric radiography 44

2.4.1 Short historical background 44

2.4.2 The uses of cephalometry 47

2.4.3 Errors of cephalometry 48

2.5 Cephalometric methods of assessing skeletal

relationship 52

2.5.1 ANB angle 52

2.5.2 Wits analysis 54

2.5.3 A-B plane angle 55

2.5.4 Ballard conversion method 56

2.5.5 A-B/functional occlusal plane angle 57

2.5.6 The archival analysis 58

2.6 Cephalometric studies on the Caucasian 61

2.6.1 Cephalometric studies on normal skeletal

relationship 61

2.6.2 Cephalometric studies on Class II skeletal

relationship 65

2.6.3 Cephalometric studies on Class III skeletal

relationship 70

2.7 Cephalometric studies in Saudi Arabia 80

2.8 Incidence of skeletal discrepancy 84

3.0 Statement of the problem and purpose of the study 90

3.1 The aims of the present study 91

4.0 Material and Method 93

4.1 Material 94

4.1.1 Criteria sample selection 94

4.1.2 Tracing technique 95

4.1.2.1 Cephalometric landmarks 95

4.1.2.1.a Definition of the landmarks 95

4.1.3 Digitization 100

8

4.1.3.1 Constructed landmarks 101

4.1.3.2 Cephalometric planes and lines 102

4.1.3.2.a The horizontal planes 102

4.1.3.2.b The vertical planes and lines 102

4.1.3.3 Angular measurements 104

4.1.3.4 Linear measurements 107

4.1.3.5 Proportional measurements 112

4.2 Assessment of method error 115

4.2.1 Assessment of cephalometric error 116

4.2.1.a Systematic error 116

4.2.1.b Random error 117

4.3 Assessing skeletal relationship 119

4.4 Assessing the skeleto-dental characteristic features of the

class II and class III groups 120

4.5 Comparison of Saudi skeleton-dental characteristics

to established cephalometric standards 121

4.6 Statistical analysis of the data 122

4.6.1 Descriptive analysis 122

4.6.2 Statistical assessment of method error 123

4.6.2.1 Dahlberg’s method error 123

4.6.2.2 Coefficient of reliability 123

4.6.3 Statistical comparison between the groups 124

4.6.3.1 Comparison between the Saudi control

group and the Saudi class II

and class III groups 124

4.6.3.2 Comparison of the Saudi control group

to established cephalometric

standards 125

4.6.3.3 The level of significance used

for comparing the samples 126

5.0 Results 127

5.1 The method error and reliability of

cephalometric landmarks 129

9

5.2 The skeletal classification of the 205

Saudi females based on ANB angle and

their distribution 134

5.3 The skeleto-dental characteristics of the

class II and class III skeletal relationship

compared to the class I skeletal relationship of

Saudi females. 136

5.3.1 Skeletal relationship 136

5.3.2 Cranial base 136

5.3.3 Maxilla 137

5.3.4 Mandible 137

5.3.5 Dento-alveolar relationship 137

5.4 Comparison of the skeletodental

characteristics of Saudi female class

I skeletal relation (control group) to

established mean value of North

American white, Riolo, et al (1974)

and British Caucasian, Bhatia and

Leighton (1993) 160



5.4.3 Maxilla 161

5.4.4 Mandible 161

5.4.5 Dento-alveolar relationship 161

6.0 Discussion 183

6.1 Material and method used 184

6.2 The method error and reliability 186

6.3 The skeletal classification of Saudi sample 188

6.4 The skeleton- dental characteristics of class II

and class III Saudi sample 189


6.4.1.a The antero posterior skeletal

relationship 190

6.4.1.b. Vertical skeletal relationship 190


6.4.3 Maxilla 193

6.4.4 Mandible 194

6.4.5 Dento alveolar relation 196

10

6.4.5.1 Maxillary incisor position 196

6.4.5.2 Mandibular incisor position 198

6.4.5.3 Inter incisal angle 199

6.5 Comparison of the skeleton-dental characteristics

of Saudi female to established cephalometric

standards 199


6.5.1.a Anteroposterior skeletal relationship 200

6.5.1.b Vertical relationship 201


6.5.3 Maxilla 202

6.5.4 Mandible 203

6.5.5 Dento alveolar relationship 203

7.0 Conclusion 205

7.1 Some suggestion for future studies 208

8.0 References 209

11

List of Figures

Figure No.

Figure 1: Illustration of angle classification 28

Figure 2: Illustration of incisor relationship classification 29

Figure 3: Illustration of class I, II, III skeletal relationship 30

Figure 4: Illustration of the angle SNA, SNB and the subtracted ANB 53

Figure 5: Illustration of Wits method 54

Figure 6: Illustration of the A-B plane angle 55

Figure 7: Illustration of Ballard’s conversion method 56

Figure 8: Illustration of the A-B/functional occlusal plane angle 57

Figure 9: Illustration of the archial analysis 59

Figure 10: Illustration of cephalometric landmarks 90

Figure 11: The computer and the digitizer used 100

Figure 12: Illustration of constructed cephalometric landmarks 101

Figure 13: Illustration of horizontal cephalometric planes 103

Figure 14: Illustration of vertical cephalometric planes 105

Figure 15: Illustration of angular measurement of anteroposterior

skeletal relationship 108

Figure 16: Illustration of angular measurements of vertical skeletal

relationship 109

Figure 17: Illustration of angular measurements of dental relationship 110

Figure 18: Illustration of linear measurements of skeletal relationship 113

Figure 19: Illustration of linear measurements of dental relationship 114

Figure 20: Pie chart of the frequency and percentage of the skeletal

discrepancy of 205 Saudi female classified by the ANB angle 135

12

List of Tables

Table No.

Table 2.8.1 Surveys of the prevalence of malocclusion based on

Angle’s and incisor classification 85

Table2.8.2 Surveys of the prevalence of skeletal discrepancy

classification 87

Table 5.1.1 The method error and reliability of cephalometric

landmarks of the angular measurements. 131


landmarks of the linear measurements 132


landmarks of the proportional measurements 133

Table 5.2.1 The skeletal classification of the 205 Saudi females

based on ANB angle and their distribution 135

Table 5.3.1.a.1 The mean and spread of measuring the ANB angle

in degrees recorded for the class I, II and III skeletal

relationship of Saudi females 139

Table 5.3.1.a.2 The mean and spread of measuring the A-B plane

angle in degrees recorded for the class I, II and III

skeletal relationship of Saudi females 140

Table 5.3.1.a.3 The mean and spread of measuring the angle of

convexity in degrees recorded for class I, II, III


Table 5.3.1.b.1 The mean and spread of measuring the SN/MP1 angle

in degrees recorded for class I, II, III skeletal


Table 5.3.1.b.2 The mean and spread of measuring the SN/occ angle

in degrees recorded for class I, II, III skeletal


13

Table 5.3.1.b.3 The mean and spread of measuring the FH/MP2

angle in degrees recorded for class I, II, III


Table 5.3.1.b.4 The mean and spread of measuring the FH/occ



Table 5.3.1.b.5 The mean and spread of measuring Y-axis angle

in degrees recorded for class I, II, III


Table 5.3.1.b.6 The mean and spread of measuring facial axis



Table 5.3.1.b.7 The mean and spread of measuring gonial angle

in degrees recorded for class I, II, III


Table 5.3.1.b.8 The mean and spread of measuring lower facial

height in mm recorded for class I, II, and III


Table 5.3.1.b.9 The mean and spread of measuring anterior

facial height in mm recorded for class I, II, and III


Table 5.3.1.b.10 The mean and spread of measuring posterior



Table 5.3.1.b.11 The mean and spread of measuring ramus



Table 5.3.1.b.12 The mean and spread of measuring

ANS-Me/N-Me in percentage recorded for

class I, II, and III skeletal relationship

of Saudi females 147

Table 5.3.1.b.13 The mean and spread of measuring S-Go/N-Me in

percentage recorded for class I, II, and III


14

Table 5.3.2.1 The mean and spread of measuring S-N in mm

recorded for class I, II, and III skeletal


Table 5.3.2.2 The mean and spread of measuring S-ar in mm

recorded for class I, II, and III skeletal


Table 5.3.2.3 The mean and spread of measuring saddle angle

in degrees recorded for class I, II, and III


Table 5.3.3.1 The mean and spread of measuring SNA angle in

degrees recorded for class I, II, and III skeletal


Table 5.3.3.2 The mean and spread of measuring A/N ┴ angle in

FH in mm recorded for class I, II, and III skeletal


Table 5.3.4.1 The mean and spread of measuring SNB angle in

degrees recorded for class I, II, and III skeletal


Table 5.3.4.2 The mean and spread of measuring facial angle

in degrees recorded for class I, II and III skeletal


Table 5.3.4.3 The mean and spread of measuring pog/N ┴ FH

in mm recorded for class I, II and III skeletal


Table 5.3.4.4 The mean and spread of measuring pog/NB



Table 5.3.4.5 The mean and spread of measuring mandibular

body in mm recorded for class I, II and III



length in mm recorded for class I, II and III


15

Table 5.3.5.a.1 The mean and spread of measuring UIE/NA



Table 5.3.5.a.2 The mean and spread of measuring UIE/A ┴ FH

in mm recorded for class I, II and III


Table 5.3.5.a.3 The mean and spread of measuring UIE/Apog



Table 5.3.5.a.4 The mean and spread of measuring UIA-UIE/NA

in degrees recorded for class I, II and III skeletal


Table 5.3.5.b.1 The mean and spread of measuring LIE/NB in

mm recorded for class I, II and III skeletal


Table 5.3.5.b.2 The mean and spread of measuring LIE/Apog in

mm recorded for class I, II and III skeletal


Table 5.3.5.b.3 The mean and spread of measuring LIE-LIA/NB

in degrees recorded for class I, II and III


Table 5.3.5.b.4 The mean and spread of measuring LIA-LIE/MP2

in degrees recorded for class I, II and III


Table 5.3.5.c.1 The mean and spread of measuring interincisal

angle in degrees recorded for class I, II and III


Table 5.4.1.a.1 The mean and spread of measuring ANB in

degrees recorded for class I of Saudi female,

North American Caucasian British Caucasian. 162

Table 5.4.1.a.2 The mean and spread of measuring AB plane

Angle in degrees revorded for Class I of Saudi female 163

Table 5.4.1.a.3 The mean and spread of measuring angle

of convexity in degrees recorded for Class I of

Saudi female 163

16

Table 5.4.1.b.1 The mean and spread of measuring SN/MP in

degrees recorded for class I of Saudi female 164

Table 5.4.1.b.2 The mean and spread of measuring SN/occ in


Table 5.4.1.b.3 The mean and spread of measuring FH/MP2

In degrees recorded for class I of Saudi female 165

Table 5.4.1.b.4 The mean and spread of measuring FH/occ in


Table 5.4.1.b.5 The mean and spread of measuring Y-axis angle

in degrees recorded for class I of Saudi female 166

Table 5.4.1.b.6 The mean and spread of measuring facial axis

angle in degrees recorded for class I of Saudi

female 166

Table 5.4.1.b.7 The mean and spread of measuring gonial angle


Table 5.4.1.b.8 The mean and spread of measuring ANS-Me

in mm recorded for class I of Saudi female 168

Table 5.4.1.b.9 The mean and spread of measuring N-Me


Table 5.4.1.b.10 The mean and spread of measuring S-Go


Table 5.4.1.b.11 The mean and spread of measuring ramus height


Table 5.4.1.b.12 The mean and spread of measuring ANS-Me/N-Me

in percentage recorded for class I of Saudi female 170

Table 5.4.1.b.13 The mean and spread of measuring S-G0/N-Me

in percentage recorded for class I of Saudi female 170

Table 5.4.2.1 The mean and spread of measuring S-N in mm angle

recorded for class I of Saudi female 171

Table 5.4.2.2 The mean and spread of measuring S-Ar in mm

recorded for class I of Saudi female 171

17

Table 5.4.2.3 The mean and spread of measuring saddle angle


Table 5.4.3.1 The mean and spread of measuring SNA in


Table 5.4.3.2 The mean and spread of measuring A/N ┴ FH

mm recorded for class I of Saudi female 173

Table 5.4.3.3 The mean and spread of measuring maxillary

length in mm recorded for class I of Saudi

female 174

Table 5.4.4.1 The mean and spread of measuring SNB in


Table 5.4.4.2 The mean and spread of measuring facial angle



body length in mm recorded for class I

of Saudi female 176


length in mm recorded for class I of Saudi female 176

Table 5.4.4.5 The mean and spread of measuring Pog/N ┴


Table 5.4.4.6 The mean and spread of measuring Pog/NB


Table 5.4.5.a.1 The mean and spread of measuring UIE/NA


Table 5.4.5.a.2 The mean and spread of measuring UIE/A ┴ FH


Table 5.4.5.a.3 The mean and spread of measuring UIE/A Pog


Table 5.4.5.a.4 The mean and spread of measuring UIA-UIE/NA


Table 5.4.5.b.1 The mean and spread of measuring LIE/NB


18

Table 5.4.5.b.2 The mean and spread of measuring LIE/A pog


Table 5.4.5.b.3 The mean and spread of measuring LIE-LIA/NB


Table 5.4.5.b.4 The mean and spread of measuring LIA-LIE/MP2


Table 5.4.5.c.1 The mean and spread of measuring interincisal

angle in degrees recorded for class I of Saudi female 182

19

DEDICATION

I am indebted with gratitude to my husband SALEH, and my

sweet kids Hashim, Talal and …… for giving me understanding, active

encouragement, fullest patience and unfailing support during the period

of the study. May Allah bless you all for everything you did for me.

I must also extend a note of gratitude to my mother, who had

encouraged me to pursue my studies and gave me her full support,

never expecting anything in return. I would like also to thank my father

and brothers especially my brother Mohammed, for their fullest

support.

Thank you very much!

20

ACKNOWLEDGEMENTS

As a Saudi Arabian citizen and a female who got the

opportunity to proceed in education to postgraduate level, there is

inevitably a number of people to acknowledge both their time and

assistance.

Firstly, I am grateful to the Kingdom of Saudi Arabia, the

Ministry of Higher Education, and King Saud University in Riyadh for

making postgraduate studies available in specialized fields. I am also

grateful to the administration at the College of Dentistry, Preventive

Dental Science Department.

Secondly, I would like to express my sincere thanks to my

supervisor, the late Professor Hafizuddin Shaikh, who did not live long

enough to witness the completion of this study. He has been an

excellent teacher and sincere guide during the early process of this

work. May Allah bless him in the hereafter.

I wish to express my sincere thanks and gratitude to Dr.

Mohammed Bukhary, Head of the Orthodontics Division, for his

immerse help, invaluable advice, and guidance in the supervision of

this thesis. I am most grateful for everything.

I would like to thank sincerely Dr. Ibrahim Masoud, for his

generosity in providing me with such valuable cephalograms of the

Saudis sample which are used in this study. I really appreciate his

kindness.

21

I would also like to thank Mrs. Vilma S. Dizon, Malou Eleazar,

Babes Lima and Cirila Libutaque for their patience in typing the

manuscript as well as Mrs. Susan Wong for producing the slides.

22

1.0 INTRODUCTION

23

1.0 INTRODUCTION

Skeletal Discrepancy has a major role in producing

malocclusion. Antero-posterior skeletal discrepancy is associated with

class II and class III malocclusion, vertical discrepancy is associated

with anterior open bite or deep bite, and transverse discrepancy with

cross bite, scissors bite and center line shifting. Its assessment is,

therefore, essential for proper diagnosis, and for planning orthodontic,

dentofacial orthopedic or orthognathic surgical treatment.

The Skeletal relationship is the underlying skeleton of the jaw,

excluding the dentoalveolar process. It may also be referred to as the

skeletal pattern or dental base relationship. It includes the jaw size, the

relationship of the jaws to each other and their relation to the cranial

base.

The skeletal relationship has been the subject of interest and

concern to many investigators (Bjork, 1947; Sassouni, 1955; Pascoe et

al., 1960; Mills, 1966; Jacobson et al., 1980; Stoelinga and leenen,

1981; Ellis and McNamara, 1984; Rosenblum, 1995).

However, most of the previous studies of the skeletal

relationship have focused on the Caucasian, and have been carried out

in Western Sociaties. In Saudi Arabia, though a number of studies had

been carried out to determine the extent of malocclusion (Nashashibi),

et al. , 1983; Al-Shammery and Guile, 1986; and Al-Emran, 1988).

The underlying skeletal morphology of Saudi population has so far, not

been well investigated (Jones, 1987 and Toms, 1989).

24

Furthermore, since one of the main aims of orthodontic

treatment is to improve the facial esthetics, a patient having skeletal

discrepancy may demand to correct the skeletal relationships as well as

the dental occlusion. Thus, in addition to the established information

regarding dental malocclusion, an accurate knowledge about the

skeletal disharmony is important for the planning and understanding of

orthodontic treatment and management.

25

2.0 REVIEW OF LITERATURE

26

2.1 Malocclusion and skeletal discrepancy

Assessment of malocclusion is an important aspect in

orthodontics, as understanding the nature of the deformity provides

keys to the planning of treatment.

2.1.1 Normal malocclusion

Normal occlusion was defined by Houston and Tulley (1986) as

the term encompassing minor deviations from the ideal that do not

continue aesthetic or functional problems. The limits of normal

occlusion cannot be specified precisely, and so there can be

disagreement between experienced clinicians about categorization of

borderline cases (for example, a minor irregularity).

2.1.2 Malocclusion

Malocclusion was defined by Houston (1983) as the term

encompassing all deviations of the teeth from the normal relation,

including a number of distinct conditions which may or may not be

independent. Such deviations involve the mal-position of the individual

teeth (rotation, tipping, over or under eruption), discrepancies between

teeth size and jaw size (crowding and spacing).

27

Several methods of classifying malocclusion have been described,

but the one which has gained most widespread use is that of Angle

(1898). Angle defined three classes of malocclusion based on the

antero-posterior relationship of the upper and lower buccal segments

(Fig. 1).

Class I: in which there was a normal antero-posterior

relationship (the anterobuccal cusp of the upper first

permanent molar occludes in the mesial buccal groove

of the lower first permanent molar).

Class II: in which the mandibular buccal segments were distal

to those of the maxilla.

This malocclusion was further divided into two

categories: class II, division I in which there was an

excessive overjet; and class II, division 2 in which the

upper central incisors were retroclined, the overbite is

greater than normal and the overjet was normal.

Class III: in which the mandibular buccal segments were mesial

to those of the maxilla..

28

Figure 1: Illustration of Angle classification

The second classification which was widely adopted was the

incisor classification (Houston, 1983) since the patients were generally

more concerned with anterior teeth correction rather than with the

buccal segments. The incisor classification was based upon the

relationship between the lower incisor edges and the cingulum plateau

of the upper central incisor (Fig. 2).

Class I: The lower incisor edges occlude with or lie

immediately below the cingulum plateau (middle part

of the palatal surface) of the upper central incisors.

29

Class II: The lower incisor edges lie posterior to the cingulum

plateau of the upper central incisors. There were two

divisions of class II:

Division 1: The upper central incisors were of

average inclination or were proclined. The overjet

was thus, increased.

Division 2: The upper central incisors were

retroclined.

Class Ill: The lower incisor edges lie anterior to the cingulum

plateau of the upper central incisors.

Class I Class II Division 1 Class II Division 2 Class III Figure 2: Illustration of incisor relationship classification

2.1.3 Skeletal discrepancy

In identifying malocclusion, it is important to look at the skeletal

relation, since it was accepted that skeletal variation was the

primary

30

cause of malocclusion. Foster (1990) defined the skeletal relationship

as the antero-posterior positional relationship of the basal parts of the

upper and lower jaws to each other, with the teeth in occlusion. When

the jaws were in their normal antero-posterior relationship in occlusion

there was a class I skeletal relationship. Any deviation from this

situation will lead to class II and class III skeletal relationships (Fig. 3).

Figure 3: Illustration of class I, II, III skeletal relationships

Foster (1990) defined skeletal class II as occuring when the lower

jaw in occlusion was positioned further backward than in skeletal class

I. It was characterized by the lower jaw in a distal or posterior relation

to the upper jaw. This was reflected by the class II first permanent

molar relationship. It has a retrognathic profile, and as a result, the

mandible was placed posteriorly relative to the maxilla with either a

small

31

mandible, a large maxilla, or a combination of both. It has increased

overjet in class II, division 1, and deep overbite in addition to a labio-

version of the maxillary lateral incisors in class II division 2. Sassouni

(1969) described this skeletal relationship by means of 2 types, the

skeletal openbite and skeletal deepbite.

Joffe (1965) defined the class III skeletal relationship as a disorder

of craniofacial growth in which the facial profile was marred by an

undue prominence of the mandible. Houston and Tulley (1986) defined

it as protrusion of the lower dental base relative to the upper. It was

typified by a concave profile with an appearance of mandibular

prognathism, a reduced or negative incisor overjet, and class III mal

occlusion. There were two basic morphologic types: the divergent and

the convergent. The characteristic features of the divergent type

include palatal, occlusal and mandibular planes which diverge, an

obtuse gonial angle, and an anterior open bite in extreme cases. The

convergent class III had palatal, occlusal and mandibular planes that

tended toward parallelism, an acute gonial angle and a deep anterior

overbite (Jacobson et al., 1974).

McCallin (1955) described class III skeletal relationship by means

of two extremes, one in which the gonia I angle was very high and the

other in which it was very low.

32

2.1.4 The role of genetic factors in the production of mal-occlusion.

A strong influence of inheritance on facial features was obvious at

a glance. It was easy to recognize familial tendencies in the tilt of the

nose, the shape of the jaw and the look of the smile. It was apparent

that certain types of malocclusion run in families (Tanner, 1989).

Malocclusion could be most probably produced by inherited

characteristics in two ways. The first would be an inherited

disproportion between the size of the teeth and the size of the jaws,

which would produce crowding or spacing. The second possibility

would be an inherited disproportion between size or position of the

upper and lower jaws, which would cause improper occlusal

relationships and the development of inter-arch variations in antero-

posterior, vertical and transverse dimensions which would produce

class 11 and/or class III skeletal discrepancy (Proffit, 1992).

Mills (1982) stated that "it is in fact generally accepted that the

genes play a large part in producing the face and the dentition of the

individuals”. Among the most famous examples of inheritance was the

Habsburg jaw of the German Royal family (Bertram, 1959), the

prognathic mandible, the protruding lower lip, and the well-known

Habsburg nose, with its prominent dorsal hump. Bertram (1959) has

illustrated the role of heredity by tracing the course of class III skeletal

33

relationship over several centuries in the Habsburgs. Of forty members

of the family for whom sufficient records remain thirty three showed

prognathism. Other authorities (Stiles and Luke, 1953; Litton et al.,

1970; Rakosi and SchiIIi, 1981) also agreed that there appears to be a

strong genetic influence in determining the occurrence of skeletal

discrepancy. Stiles and Luke (1953) pointed out that skeletal

discrepancy was inherited via a dominant gene with an unknown

degree of reduced penetrance. Litton et al. (1970) found in studying the

influence of inherited tendencies that, one third of a group of children

who presented with severe class III malocclusion had a parent with the

same problem, and one sixth had an affected sibling. Rakosi and

SchiIIi (1981) mentioned that the growth and size of the mandibular

base was predetermined by heredity. Harris and Johnson (1991)

examined longitudinal cephalometric radiographs and dental casts of

siblings who participated in the Bolton-Brush growth study. They

concluded that the heritability of craniofacial (skeletal) characteristics

was high, but that of dental characteristics was low.

2.1.5 The role of environmental factors in the production

of malocclusion.

There is no doubt, however, that environmental factors play a role

in the establishment of facial proportions and dental relationships.

34

Environmental influences during the growth and development of the

face, jaws, and teeth consist largely of pressures and forces of

physiologic activity (Watson et al., 1968; Warren, 1984; Turvey et al.,

1984; Proffit, 1992). Function must adapt to the environment, as when,

chew and swallow were determined by diet because pressure against

the jaws and teeth affect jaw growth and tooth eruption. When function

could affect the growth of the jaws, altered function could be a major

cause of malocclusion (Proffit, 1972; Steedle and Proffit, 1985). But

when the function makes little or no difference to the individual's

pattern of development, altering the jaw function would have little if

any impact etiologically or therapeutically (Proffit, 1992).

References have also been made to environmental disturbances

such as trauma, sucking habits, and childhood illness as contributing to

the wide dento-facial variations that arise, even within families (Shaw,

1992).

Thompson and Jurgens (1956) described several acquired factors

which may produce the class III skeletal relationship. Included in their

list was trauma (such as fractures of the mandible) and even certain

infections such as osteomyelitis of the mandible which on occasion

may produce a hyperplastic reaction resulting in class III skeletal

relationship. Rakosi and Schil I (1981) pointed out that a flat anteriorly

located tongue was also responsible for the anterior position of the

mandible, and that the children with skeletal discrepancy can have

contributing habits; there was

35

a positive habit history in 64% of cases (in children without

malocclusion, it was 54%).

Mouth breathing, especially in patients with enlarged tonsils, can

likewise promote the development of skeletal discrepancy (Niinimaa,

1981; Harvold, 1981). The tongue of mouth breathers was always fiat,

which causes a wide mandibular dental arch and narrow maxillary arch

with a high palate.

Occlusal force with unfavorable incisal guidance can also

promote the skeletal discrepancy (Rakosi and Schilli, 1981).

36

2.2 Growth of the cranio-facial skeleton.

Enlow (1990) defined the facial growth and development as a

morphogenic process working toward a composite state of structural

and functional balance among all of the hard and soft tissue parts.

Facial growth was a complex phenomenon and its understanding

requires the study in depth of the changes that occur from infancy to

adulthood. However, the clinician should be aware of the basic

principles underlying the growth mechanisms, for they are significant

when assessing the etiology of malocclusion and the possible method

of treatment (Nielsen, 1991).

2.2.1 Growth mechanisms

The theory that bones grow by simple symmetrical enlargement

was wrong (Enlow, 1975). Such a simple growth mechanism could not

possibly create such a complex and differentiated morphology as that

of the mandible or maxilla. Such morphology demands differential

growth mechanisms, and different types of development for the

individual bones.

The following three mechanisms are important for the growth:

2.2.1.a Cortical drift (increase in size).

Direct bone growth by means of deposition and resorption

processes on the bone surfaces, cause the cortical plate to drift (Enlow,

37

1975). The bony cortical plate drifts by depositing and resorbing bone

substance on the outer and inner surfaces, respectively, in the direction

of growth. When, due to cortical drift, all other parts of structure

undergo shifts in relative position, this movement was termed

relocation. During the developmental period, deposition takes place at

a slightly faster rate than resorption, so that the individual bones slowly

enlarge.

2.2.1.b Displacement.

Apart from direct bone growth due to deposition and resorption, the

second process of growth mechanism which takes place was termed

displacement, i.e. the translatory movement of the whole bone caused

by the surrounding physical forces of adjacent structures. The entire

bone was carried away from its articular interfaces (sutures, condyles)

with adjacent bones. Displacement in conjunction with bone's own

growth was termed "primary displacement" (Enlow, 1990). But

displacement due to the enlargement of bones and soft tissue which

were not immediately adjacent was termed "secondary displacement"

(Enlow, 1990). Displacement was initiated by the sum of the expansive

forces of the soft tissues in the growing face creating a space around

the contact surfaces into which the bone can enlarge. The degree of

displacement equals the amount of new bone deposition, although the

direction of displacement was always opposite to that of the bone

deposition.

38

2.1.c Remodeling (change in shape).

As a result of relocation and displacement, further adaptive bone

remodeling was necessary in order to adjust the shape and size of the

area to the new relationship. Selective resorption and apposition

processes functionally remodel the area to conform to the new

physiological loading. The information which initiates the remodeling

process was contained within the various soft tissues surrounding the

bone.

2.2.2 Growth of the midface.

The horizontal growth of the mid face was determined by the

expansion of the anterior cranial fossa, which enlarges anteriorly to an

extent that matches the sagittal development of the maxilla. The

resorption and deposition processes on the endocranial and ectocranial

. surfaces lead to displacement and remodeling of the underlying

structures (nasal bone, ethmoid bone). Thus, the horizontal

development of the midface was balanced inferiorly with the antero-

posterior elongation of the maxilla and superiorly with the horizontal

extension of the anterior cranial fossa.

2.2.3 Maxillary growth.

Maxillary remodeling involves bone deposition on the posterior wall

of the maxillary tuberosity, resulting in a posterior lengthening of the

39

bony maxillary arch (Bjork and Skieller, 1974). Deposition on the

outer surfaces of the tuberosities and resorption on the inner surfaces

causes the cortical plate to drift in a backward direction. This posterior

elongation of the upper jaw was coupled with primary displacement of

the maxilla which was directed anteriorly and exactly equals the

amount of posterior lengthening.

Due to growth of the middle cranial fossa, the maxilla, the

anterior cranial base, the forehead, and the zygoma were shifted in a

forward direction. This process leads to secondary displacement of the

maxilla, i.e. it was displaced passively due to expansion of the middle

cranial fossa without the growth processes of the maxilla itself being

directly involved.

During vertical displacement of the midface, the maxillary arch

was displaced in a downward direction due to resorption on its nasal

surface and simultaneous deposition on its palatal surface. The

downward movement of the maxilla was usually not parallel, but

differs anteroposteriorly. The result was a rotational movement of the

maxilla.

2.3.4 Mandibular growth.

Contrary to previous theories, the condyles do not govern the

growth of the entire mandible, but act locally. Some theorists such as

40

Bjork (1968) and Petrovic (1974) claimed that the pressure exerted on

the

glenoid cavity by the growing condyle caused displacement of the

mandible out of articular contact. However, experiments have shown

that, even after condyles have been removed, the mandible can assume

a normal position which indicate that the condyle was irrelevant to the

growth of other mandibular structures.

When assessing mandibular growth, it should be remembered that

the mandibular corpus during its remodeling was elongated posteriorly

by the same amount as the maxilla (Enlow, 1990). Elongation of the

mandible toward the ramus was possible because the anterior surface

of the ramus was remodeled by resorption into the elongated

mandibular corpus. Simultaneously, the entire mandible was displaced

anteriorly by an amount that equals the maxillary displacement

(primary displacement). The posterior sections of the ramus and

condyles grow diagonally upward and backward, and increase in height

by the same amount of the naso- maxillary complex and middle cranial

base. Growth of the middle cranial base also leads to secondary

mandibular displacement. As the expansion of the middle cranial fossa

is directed forward, a horizontal growth of the ramus will take place.

Simultaneous to the drift of the lower teeth, remodeling takes

place around the chin. Resorption on the outer edge of the anterior

alveolar region and bone deposition on the anterior and inferior

external contours of the symphysis caused the chin to become more

prominent.

41

2.2.5 Intermaxillary relationship.

Simultaneous to maxillary remodeling, active apposition and

resorption processes in the bony alveolar sockets, leads to vertical drift

of the upper teeth. Further, lowering of the upper dentition results from

displacement of the maxilla. Once the upper teeth have moved into

place, an upward drift of the lower teeth and their alveolar processes

commences, thus establishing the final occlusion (Houston and Tulley,

1986).

2.2.6 Growth considerations.

A few basic principles of maxillary and mandibular growth should

be stated here. On average, the peak of the growth spurt occurs at 12

years in girls and at 14 years in boys (Burstone, 1958; Graber, 1972).

The maxilla and the mandible grow in both a downward and forward

direction relative to the cranial base. At the peak of the juvenile growth

spurt (7 to 9 years of age), the maxilla grows 1mm/yr and the mandible

3mm/yr, whereas during the prepubertal period (10 to 12 years of age)

there would be a reduced rate of growth (maxilla 0.25 mm/yr,

mandible, 1.5 mm/yr), only to reach maximum growth levels during

puberty (12 to 14 years of age, maxilla, 1.5mm/yr; mandible,

4.5mm/yr), (Bjork & Skieller, 1972; Behrents, 1986). Overall

mandibular growth was approximately twice that of overall maxillary

growth (Love et al., 1990).

42

2.3 Racial variation.

Population differ in their character, size, growth and shape. These

differences are due to a complicated interaction of genetic and

environmental factors (Tanner, 1989). Distinctions between races by

geographical location, historical origins, culture or language

(Montague, 1942) were usually subsumed into three major racial

groups: Asiatic (or Mongoloid), Black (or Negroid), and White (or

Caucasian) (Montague, 1942; Coon et al., 1950). The classification of

three groups gave each group its own characteristics, which in general

serve to distinguish them from each other.

However, research studies and anthropological findings indicate

that not only did each racial group had its own standards (Miura, 1968;

Drummond, 1968; Guo, 1971; and Baccon et al., 1983), but within the

same race, each subgroup had its own standards, (Burstone, 1958;

Holdaway, 1983; and Nashashibi et al., 1990).

From the above it will be seen that it is illogical to apply the

standards of one racial group to another, or, within the same race, to

apply the standards of one subgroup to another (Cotton et al., 1951;

Kowaliski et al., 1974; Richardson, 1980; Houston and Tulley, 19860).

The literature showed that a lot of studies had been done to

determine the mean values or norms of different subgroups (Bjork,

1947; Steiner, 1953; Hajighadimi et al., 1981; and Haralabakis et al.,

1983).

43

Nevertheless, very little scientific information was available on the

physical characteristics of Arabs. Although Arabs are Caucasian

(Coon, et al., 1950), there is hardly any published scientific research

related to the population of Arabian Peninsula (the Saudi Arabians)

Masoud (1981). However, since they are Caucasians, we can use

established data of Caucasians as a reference for comparison with the

expected variations within the subgroups.

44

2.4 Cephalometric radiography.

Moyers (1988) defined cephalometric radiography or

cephalometrics as a standardized technique employing oriented

radiographs, for the purpose of making head measurements.

2.4.1 Short Historical Background

The principles of cephalometries are patterned closely after the

science of craniometry, which has long been used in anthropology in

the quantitative study of dry skulls, since the head was a fertile area

for researchers in the fields of art, anatomy, and anthropology.

Camper (1722-1792) was one of the first workers to measure the

relationship of the face to the head. He was probably the first to

employ facial angle in measuring the face and its relation to the head

for anthropological studies. The facial angle was formed by the

intersection of the facial line and the horizontal plane. The first line

passes from the most prominent point on the forehead to the point of

contact of the lips, the second line from lower part of the nasal

aperture backward through the center of external auditory meatus. By

using this index, Camper was able to categorize the form of the

crania.

In the nineteenth century, craniologists started to develop

craniostat for orienting dried skulls in order to compare crania, and

began to introduce new baselines. Broca (1873), the inventor of

cephalic index, introduced a new baseline called "plan alveolo

45

condylion" which passes through the alveolar point and tangent to the

inferior surfaces of the two occipital condyles. Von lhering (1872)

introduced a plane which was considered the most important to

evaluate the facial profile and it was accepted by the Anthropological

Congress in Frankfort in 1882 and named the "Frankfort plane". This

line was drawn from the center of each auditory meatus to the lowest

point on the inferior margin of each orbit and which was modified

later on, so that the plane passed through the upper borders of the

bony meati above their centers. With the advent of cephalometric

technique the Frankfort plane remains one of the most important

orientation landmarks.

The discovery of x-rays by Roentgen (1895) allowed

anthropometric examination to utilize profile radiographs of the skull

to obtain a better understanding of the orientation of bones and soft

tissues, thus expanding the horizon of craniometry and cephalometry.

Pacini and Roentgen (1922) won a research award offered by the

American Roentgen Ray Society for his thesis entitled "Roentgen Ray

Anthropometry of the skull". Pacini believed that his procedure would

be useful in the study of human development, classification and

deviations. He recorded a technique for producing and measuring the

anatomical structures of both dried skull and living human head by

roentgenographic projection on lateral head plates. He also identified

certain anthropologic landmarks on the roentgenograms e.g. gonion,

pogonion, nasion, anterior nasal spine.

The simultaneous introduction of the cephalostat in 1931 by

46

Broadbent in USA and by Hofrath in Germany, allowed the head to be

held in a fixed position relative to the x-ray source and to the film. This

proved to be a most important contribution to radiographic assessment

of the facial and skeletal form. The Broadbent cephalostat consisted of

a head positioning device in which the head was secured by ear posts

inserted into the ear canals. A calibrated scale enables the head to be

centered in the machine, and orientation of the head in the Frankfort

horizontal plane was accompanied by means of a pointer to the left

orbital. This pointer lies at the same horizontal level as the top of the

ear posts. The head was locked in this position by means of a rest

which engages the bridge of the nose. Two x-ray tubes were used, one

for lateral and the other for frontal head plates. In the case of the lateral

exposure, the central ray passed along a line joining the ear posts, at

right angles to mid sagittal plane and the film. The exposures are made

at a target distance of five feet, thus ensuring that the enlargement of

the image was slight.

2.4.2 The uses of cephalometry

The cephalostat provides a means of taking standardized lateral

skull radiographs, thereby, facilitating the measurement of living

subjects. This led to the wide spread employment of cephalometrics as

an analytical tool to estimate craniofacial morphology, measure growth

changes, and predict future relationships. As diagnostic aid to evaluate

dento-facial anomalies, it clarifies the anatomic basis for malocclusion

and the changes brought about by orthodontic treatment (Moyers,

47

1988).

Down (1952) stated "cephalometrics is to the orthodontist what

the dissection room is to the anthropologist and anatomist". Indeed,

cephalometrics had progressed to the point where it was no longer the

tool of research workers only, but was a necessary adjunct to a

complete and well planned case analysis from which a diagnosis may

be derived. It was not a panacea that will supplant all other methods of

analysis and answer all the orthodontists diagnostic problems, and it

can never take the place of clinical observation. But as long as the

science of orthodontics is the study of relations within the dento-facial

complex in which "all we ever find are variations, endless

variations"(Simon, 1926), then cephalometrics will be an invaluable

tool supplementing all other procedures of analysis.

2.4.3 Errors of cephalometry.

The development of cephalometries has created a need for

exactly locating an increased number of landmarks on head film. These

landmarks can be used as registration marks for measurements, or for

the superimposition of films in a series of examinations.

It is known that differences can occur when locating

cephalometric landmarks. By comparing the variation in a number of

measurements of different landmarks it was possible to conclude

which landmarks were most reproducible (Midtgard et al., 1974).

Some of the landmarks, used clinically, were located on the

48

outlines of the cranium and were comparatively easy to identify due to

the sharpness in contrast of the head film. The structures of the inner

cranium were, on the other hand, often indistinct because of

summations of superimposed anatomical details (Hixon, 1956).

Bjork (1947) has mentioned three reasons for errors of method in

cephalometric measurement studies:

1. Differences between two films of the same individual.

2. Differences caused by variation of the positioning of the

landmarks.

3. Errors in the reading process.

His analysis of errors of method reveals large differences in

precision when locating different cranial landmarks. Only minor errors

in measurement have, however, been established with landmarks

which are easily identifiable. Linear errors of measurement in these

cases vary between 0.3 mm and 1.4 mm and angular errors of

measurement between 0.3 degrees and 1.6 degrees.

Richardson (1966) had two judges register cephalometric

landmarks, lines, and angles on ten cephalograms with an interval of

one week. He found that ordinary cranial landmarks have a margin of

error of less than +1 mm. Vertical deviations rise towards higher

counts when anatomical curves in the profile are involved. Horizontal

deviations have also been observed and all angular measurements have

followed the tendency to variation of the landmarks.

Double registrations of size and direction of facial growth have

shown minor deviations in a study carried out by Lundstrom (1968) in

49

which forty-one pairs of twins were registered both initially and after

thirteen years. A noticeable difference in the pattern of growth has,

however, arisen depending on whether the head film has been

orientated from the anterior or posterior skull base. The conclusion has

been drawn that growth analyses based on lateral cephalometric head

film do not give a sufficiently objective picture of the character of the

growth changes.

Linder-Aronson (1970) has estimated the degree of error in

cranial distance measurements by calculating the variance of error for

the differences in distance in relation to the variance of the distance in

the material as a whole. The variety of error has, with few exceptions,

amounted to less than three per cent of the total variation.

Baumrind and Frantz (1971) have found that landmarks nasion

and menton which are placed anatomically on the bony edges are easy

to identify, whereas landmarks which are placed on curves with wide

radii show proportionally greater errors of measurement. They have

statistically concluded that the probability of placing sixteen landmarks

correctly is forty-four per cent.

Houston et al. (1986) mentioned in assessment of reproducibility

of the measurements that two types of errors should be estimated, the

systematic and random errors.

The systematic error is not easy to detect and it is associated with

the particular instruments or technique of measurement being used. It

can originate from the faulty calibration of equipment, or from bias on

the part of the observer. For example, if measurement from two

50

different studies are compared and it is assumed incorrectly that the

magnification are the same, the comparison is biased. These errors

must be estimated from an analysis of the experimental conditions and

techniques. On the other hand the random error is produced by a large

number of unpredictable and unknown variations in the experimental

situation. The precision of an experiment is dependent on how well we

can overcome or analyze random errors. Example of this error is

tracing error which may be caused by the lack of clarity of

cephalometric landmarks due to superimposition of structures, or the

blurring of the image brought about by movement during exposure.

These errors can be neutralized in studies by studying a sample of

adequate size and by tracing each film more than once (Gravely and

Benzies, 1974).

2.5 Cephalometric methods of assessing skeletal

relationship.

There are different methods of assessing the degree of skeletal

discrepancy. It would be very difficult to include them all, and only the

most commonly and widely used methods will be reviewed. These

methods are:

2.5.1 ANB angle.

ANB is the most widely used method to assess skeletal

relationship. It is the result of subtracting SNA from SNB. Although it

is known as Down method, Riedel (1950) was actually the first to

51

suggest using the angle ANB to measure the anteroposterior apical

base relationship. Riedel (1950) found the angle to have a mean value

of 3.4° based on a small sample of cases with good profiles (beauty

queens) rather than good occlusion. On the other hand, Steiner (1953)

found the mean value for ANB to be 2° in his analysis based on normal

occlusion

Figure 4: Illustration of the angle SNA, SNB and the subtracted ANB

angle

Although the ANB angle is used extensively in everyday clinical

practice, under the name of Down's analysis, for the assessment of the

skeletal relationship, there are some shortcomings in the method. The

ANB angle is known to be affected by the absolute value of angle

SNA, which in turn, is influenced by variations in the horizontal or

vertical position of nasion or the slope of SN plane. Rotation of the

jaws relative to the anterior cranial base also alters the position of A

and B points, and hence, the value of ANB (Richardson, 1982).

52

2.5.2 Wits analysis.

The second most commonly used method is Wits analysis

(described by Jacobson in 1975). Wits is an abbreviation for the name

of Wits Watersrand University in South Africa. The method relies on

the projections of perpendiculars from points A and B onto the

functional occlusal plane at AO and BO. The horizontal distance

between the points AO and BO is found on average to have a value of

zero in females. In males AO is 1 mm behind BO.

Figure 5: Illustration of Wits Method

The main disadvantage of this method is that it lies in the

difficulty of accurately drawing the functional occlusal plane. This

has a direct effect on the reading (Brown, 1981) especially in

growing children, where the premolars are partially erupted. In

addition, to the need for magnification as a linear measurement, there

is besides the difficulty in identifying point A.

53

2.5.3 A-B plane angle

The third method is described by Down (1948) as the angle

formed between the A and B planes and the facial plane (N-Pog).

Positive and negative signs were used to .denote the relative protrusion

of the mandible. The mean value of this angle was found to be minus

4.6 in a study of twenty cases with excellent occlusions.

Figure 6: Illustration of A-B plane angle

The shortcoming of this method is the influence of the horizontal or

vertical position of point nasion, and the difficulty in identifying point

A.

54

2.5.4 Ballard Conversion Method

Ballard (1948) devised a method based on the incisor tooth

position for assessing skeletal pattern. This method assumes that if the

upper incisors are within the average variation of angulation to the

maxillary plane and lower incisors within the average variation of

angulation to the mandibular plane, then, the residual overjet will

approximately reflect the anteroposterior dental base relationship.

Figure 7: Illustration of Ballards Conversion Method

In the above concept, there is the basic assumption that the ideal

tooth position in relation to dental base will indicate the skeletal

relationship. Houston (1975) examined Ballard's method and criticized

it on the grounds that :

i] The relationship between the base and the developmental position

of the incisors was not invariant.

ii] There was no justification for using the mean values for the

55

correction of the incisor angulation, because at best they were

only arbitrary.

iii] The classification depended upon whether the incisors were

rotated at the apex or the apical third of the root.

2.5.5 A-B/functional occlusal plane angle

Houston and Tulley (1986) described a method to assess the

anteroposterior skeletal relationship. The method uses the AB planeand

the functional occlusal plane and measure the angle formed between

the two planes.

Figure 8: Illustration of A-B/Functional occlusal plane angle.

In a class I skeletal pattern, the range was found to be 85° - 95°.

More than this value will indicate class II skeletal relationship and less

than this value will indicate class III skeletal relationship. Similar to

Wits analysis, this method is affected by any variation in the

orientation of the occlusal plane.

56

2.5.6 The Archial Analysis.

The least used method is the archial analysis of Sassouni (1955).

His analysis is unique in that it does not employ a set of established

norms, but rather defines the relationships within the individual pattern

as normal or abnormal in anteroposterior and vertical directions. It is

constructed from five horizontal planes and tend to intersect a central

area "0". From this area "0" five arcs were drawn, the first one called

the anterior arc. In a class I skeletal relationship, ANS and Pog should

be located on an anterior arc. In a class II skeletal relationship, Pog is

posterior to the anterior arc, or ANS is anterior to this arc. In a class III

skeletal relationship Pog is anterior to the anterior arc, or ANS is

posterior.

Figure 9: Illustration of the archial analysis

57

The shortcomings of this analysis are that:

i) the landmarks used were not easy to locate,

ii] not easily understood by everyone.

From the above, it will be seen that each method used to measure

the anteroposterior relation of the maxillary and mandibular dental

bases has its own merits and demerits. However, the first method of

analyzing skeletal discrepancy i.e. ANB angle is the one which is most

widely

adopted, and accepted by the clinician and researchers as the most

reliable method to achieve their purpose (Freeman, 1981). It has

became part of everyday clinical practice and is considered as a must

for each cephalometric analysis (Enlow, 1990).

2.6 Cephalometric Studies on Caucasian Population.

2.6.1 Cephalometric studies on normal skeletal relationship.

Baum (1951) carried out a study on 62 children. The subjects were

equally divided by sex and all had clinically excellent occlusions,

considering tooth relationships only. The mean age for the males was

12 years 8 months +1.29 months and for females 12 years 7.5 months +

1.56 months. The landmarks and planes used were those employed by

the ANB angle. He found that though the angle of convexity of the

male was higher than that of females, no other significant differences

in the skeletal or dental patterns of the sexes were to be observed.

However, when compared to Down's group, this younger group was

58

shown to have more convex faces, less upright incisors in relation to

either the occlusal plane or mandibular plane and a more protrusive

denture. The author, therefore, came to the conclusion that it was

important to appreciate the differences in the skeletal and denture

patterns of adults and children.

Goldsman (1959) used 50 individuals selected by a panel for

"harmony of facial balance and proportions", which he called the

Indiana sample. This sample was found to include some convex and

some concave facial types. Every individual displayed a class I molar

relationship. When compared with Downs analysis, the measurement

of the Indiana sample were similar to those of Downs with the

exception of the facial angle and the Y-axis angle, where significant

differences existed. The range of extremes of all measurements of the

Indiana sample was wider than that of Down's sample; all of Down's

denture measurements, as well as the Frankfort mandibular planes

angle and angle of convexity had smaller standard deviations than

those of the Indiana sample who were disposed towards the

retrognathic or class 11 side of Down's findings.

An investigation involving a comparison of facial and dental

parts of children of similar ethnic origin but living in different

countries was carried out by Gresham (1963). It involved 23 males

and 21 females (Whites) living in North America and a similar group

of New Zealand children. The individuals in each group were of

similar age, sex, occlusion and ethnic origin. Quite a marked overall

similarity was found in the basic skeletal pattern. The New Zealand

59

child tended to have a more obtuse saddle angle, but the effect of this

upon the facial pattern as a whole was cancelled out by the relatively

longer mandibular body in the New Zealand child. The general

relationship to the cranial base of the chin and the facial plane was,

thus, practically identical in the two groups. However, differences

were noted in facial height and the overall protrusion of the incisor

teeth which tended to be greater in the New Zealand child.

Taylor and Hitchcock (1966) introduced the 'Alabama analysis'

based on a study of 17 boys and 23 girls from the ages of 8-15 years.

A total of 32 measurements were made from the tracings of each

of the 40 subjects, out of which the authors selected 16 which formed

the Alabama analysis. Only one measurement, upper incisor to SN

plane, showed a value large enough to indicate a questionable

difference between boys and girls might have been revealed if the

sample had been larger. However, when comparing their

measurements with available data from other similar studies carried

out on American white children, 6 measurements were found to be

significantly different, which led the authors to the conclusion that they

were dealing with a different population and that the ethnic

background of Southern white children is different enough from that of

children in other sections of the country to warrant a separate

cephalometric standard. In the course of their study, Taylor and

Hitchcock also related certain cephalometric points to the Frankfort

plane and to other reference planes. In every instance, they found that

each measurement relative to the Frankfort plane showed a larger

60

standard deviation or spread than the corresponding measurement to a

plane other than the Frankfort plane. Thus, they concluded that the

Frankfort plane was not reliable enough and based their analysis on the

SN line as a reference.

Cephalometric measurements on 50 English and 50 Indian adults,

equally divided as regards sex, were compared for sex and group

differences by Iyer and Lutz (1966). Evaluation of their average

measurements indicated that the female facial size was generally

smaller than the male's. The Indian face was not prognathic but was

smaller with smaller facial and gonial angles, and more proclined

lower incisors, when compared with the English. The authors also

claimed that it was possible to classify the individuals by sex, and

assign them to the Indian or English group with an 80% accuracy,

using 14 measurements. They also arrived at the conclusion that the

SN line, maxillary plane and Frankfort plane were all equally suitable

for assessing upper incisor inclination.

Christie (1977) looked at the dentofacial cephalometric patterns

of adults possessing near ideal occlusions. His sample consisted of 82

caucasian adults (43 females and 39 males), and was divided into

individuals with a vertical (dolichofacial) pattern or a horizontal

(brachyfacial) pattern. His major finding was that normal occlusion

occurs more commonly in individuals who tend to have brachyfacial

skeletal pattern. A clear trend showed that the more brachyfacial a

person, the greater the likelihood there was of their having a normal

occlusion. These individuals were shown to have a greater distance

61

from the maxillary first permanent molar to the upper central incisor,

and also a greater distance from pterygoid vertical to the maxillary first

permanent molar. Because they experience more horizontal growth in

the jaws, they have larger arches and therefore less crowding,

supported by an increase in intercanine and intermolar widths. The

author felt that this may have profound implications for treatment

planning in that there may be less need for extractions in order to

achieve good occlusions.

Scheideman et al. (1980) carried out a comprehensive

cephalometric analysis of "normal" adults. Fifty six adult caucasians

with class I skeletal and dental relationships and good vertical facial

proportions were analyzed morphologically with a computerized

craniofacial model. The study was designed to establish cephalometric

norms for soft tissue, skeletal and dental relationships of a "normal"

adult population. With few exceptions, the skeletal and dental

relationships were found to be in close agreement with previous

studies.

Schmuth et at. (1988) based their study on 393 cephalograms

taken at the beginning of orthodontic treatment. The mean values of

some commonly used cephalometric angles were calculated and

compared with the corresponding values given in the literature. The

result of this comparison was that there were surprisingly small

differences between these values based on an unselected mal occlusion

group and those in the literature which were mostly based on "normal"

occlusion patients. All the parameters measured showed a high degree

62

of variability.

2.6.2 Cephalometric studies of the class 11 skeletal relationship

Blair (1954) studied 40 class I subjects; 40 class 11, division I

subjects; and 20 class II, division 2, subjects. They had an age range of

10 to 14 years. The only mandibular difference was a greater gonial

angle in the class I males. There were no differences in the females.

There were no differences in mandibular position between class I and

class H. Blair noted great variation in the subjects and the possibility

of a forward position of the maxilla in class H.

Altemus (1955) based his study on 40 girls (20 class H, division

1, and 20 controls) and found that the class H maxillae were more

protrusive and that the mandibles were normal in size.

Sassouni (1969) reported the skeletal class H type could be due to

positional deviation, dimensional deviation or both of them.

Positional deviation can be viewed as a mismatching of

characteristics of the open bite and deep bite types. The skeletal class

H borrows the long anterior cranial base from the open bite, as well as

the short ramus, but the small gonial angle was from the deep bite. The

palate is tipped downward and backward as in the open bite. The result

of these combinations was a protrusive maxilla, a retrusive mandible,

or both and angle class H mal occlusion.

Dimensional deviations were due to two major disproportions,

the large maxilla and the small mandible. The large maxilla was

characterized by a palate in which the posterior nasal spine was

normal.in position but too long for the rest of the face, but the

63

mandible was normal in size and position. The small mandible was the

most frequent cause of dimensional class 11 skeletal type. The corpus

was short and the gonion was in the normal position which leads a

retrusive chin. Dental crowding, ectopic eruption and impaction were

seen in these cases. The discrepancy between the maxilla and the

mandible kept the lips apart.

Hitchcock (1973) studied one hundred and nine (fifty seven

female and fifty two male) class 11, Division 1 malocclusions

documented from cephalometric head films, and compared them with

forty normal occlusion cases. The classification was made from models

and photographs according to Strang’s first six steps (1958). The age

range was from 7 years to 28 years. He found that the position of

maxilla was not significantly different from that of normal occlusion

sample (SNA), but SNB measurement was smaller in class 11 division

1 malocclusion. The ANB was greater which led to a retruded position

of the mandible. The angle of occlusal plane to SN plane in class 11

cases showed no significant difference from that measurement in the

normal occlusion sample. However, the angle of the mandibular plane

to sella nasion, and the Y- axis angle were greater in class 11, division

1, than in normal occlusion. The lower incisors showed no highly

significant difference between class 11 subjects and the normal

controls but the upper incisor to N A measurement and the overjet were

protruded in class 11, division 1 subjects, while thy lower incisors had

a normal position when compared to normal occlusion.

McNamara (1981) analyzed lateral cephalometric radiographs of

64

227 children (153 males and 124 females) between the ages of 8 and 10

years, with class 11 molar and cuspid relationship. The results were

compared to norms available in the literature. He concluded that only a

small percentage of his subjects showed maxillary skeletal protrusion

while the highest percentage showed maxillary retrusion. Mandibular

skeletal retrusion was the most common feature. He also found the

degree of maxillary dental protrusion was less than that reported by

most previous investigators and the lower incisors were usually well

positioned. However, there was some dental protrusion and retrusion.

Almost half of the sample exhibited excessive vertical development.

Giorgio and Lucchese, (1982) evaluated the shape, size and

position of the mandible in class II, division 2 malocclusion based on a

sample of 60 subjects (38 male and 22 female) with class II, division 2

malocclusion, and a control sample of 28 subjects (13 male and 15

female) with normal occlusion. The age range in each sample was 9 to

14 years. By analyzing the cephalometric radiographs they found the

mandible of subjects with class II, division 2 mal occlusion tend to

have a unique skeletal pattern of the face, characterized by a hyper

development of the component parts of the mandible (ramus height and

the body) and a small gonial angle.

Amoric (1985) conducted a study of 100 French subjects and

analyzed McNamara's linear measurement for the maxilla and

mandible. He found statistically significant differences in the means

and distribution of his results. Amoric's mean was more protrusive for

point A and less retrusive for pogonion. No indication were given on

65

the age of the subjects or the degree of skeletal dysplasia in the

sample. As noted by Amoric, McNamara's sample had excessive

anterior vertical dimension. Amoric's sample consisted of more

horizontal growers than McNamara's, thus leading to less mandibular

retrusion.

Sarhan and Hashim (1994) studied a random sample of 150

British school children aged 9 to 12 years. Lateral skull radiographs

were taken and traced. Out of the sample, 41 children (18 boys and 23

girls) were selected on the basis of an ANB angle> 4.5 degrees, as

having a class 11 skeletal relation. The 41 class 11 skeletal sample was

divided according to the value of SNB angle into subjects with normal

anteroposterior positioned mandible (SNB >76°, 19 children) and

retruded mandibles (SNB <75.5°, 22 children). 16 angular and 8 linear,

skeletal and dental parameters were used. They found the retruded

mandibles had retruded maxillas with retruded chins, increased vertical

development and facial height, normal proclination of lower incisors.

The normal mandibles were characterized by protruded maxillas with

protruded chins, decreased vertical relationship and normal facial

height, and the anterior proclination of lower incisors.

Rosenblum (1995) studied 103 (36 male and 67 female) subjects

with class 11 skeletal pattern which was assessed by Down (1948)

angle of convexity and the Kim (1978) anteroposterior dysplasia

indicator (APDI). Age selection was based on skeletal maturity

assessment method used by Fishman (1979). The skeletal age was

divided at three levels of skeletal maturation (SMI 1-3, SMI 4-7, SMI

66

8-11). Chronological age ranged from 12 - 16 years. He found that the

dominant pattern was maxillary protrusion with normal mandible. The

angle NA-FH (Lande 1952) indicated the incidence of maxillary

protrusion in the three groups was 56.3%. Using N-A to FH as

reference showed that SNA (Steiner, 1953) under - reported maxillary

protrusion 39 % of the time, but the reporting of A to nasion

perpendicular (McNamara, 1984) was close at 53.5%. The facial angle

(Down, 1948) indicated that only 26.7% had mandibular retrusion.

Using the facial angle for mandible as reference showed that SNB over

- reported mandibular retrusion 46 % of the time and Pog to nasion

perpendicular (McNamara, 1984) over reported this 40% of the time.

2.6.3 Cephalometric studies of the class III skeletal relationship.

Bjork (1947) conducted a study on 281 Swedish conscripts

between the ages of 21 and 23 years. Twenty six cases presented class

III skeletal relationship. These were compared to the whole sample on

the basis of mean values. He found that the maxillary base was slightly

more

retrognathic than the mean value for the whole material. The

mandibular base was slightly more prognathic. The maxillary incisors

showed an average forward inclination and the mandibular incisors a

backward inclination. There was a reduction in the saddle and joint

angles and a shortening of the vertical part of the cranial base (sella-

articulate). These were accompanied by a shortening of the cranial

base from nasion to articulare. He found also that in the class Ill, the

67

mandible had a greater gonial angle, a more acute angle was formed

by the occlusal plane with the lower border of the mandible, and there

was a narrower anteroposterior width of the ramus.

Stapf (1948) studied 37 class III facial patterns without regard to

age, sex, or severity of deformity. The mean pattern was compared to

that of 21 individuals, eight years of age, with normal occlusion. In the

class III pattern, the posterior end of the occlusal plane was lower and

the anterior end higher than in the normal. The angle formed by

symphysis and lower border of the mandible was more acute.

Sanborn (1955) made an excellent cephalometric study of 42 (26

males and 16 females) class III skeletal relationship adult patients

compared to 35 (26 males and 9 females) adult controls, age ranging

from 16 to 38 years. He found that for the angular measurements, the

class III facial pattern showed a middle face deficiency and more

prognathic mandible than the normal, resulting in a concave profile

which was a most striking feature of the class In deformity. The ramus

of the mandible in the class III group formed a more acute angle with

anterior cranial base and upper face than is normal, which had the

effect of positioning the gonion further forward. The gonial angle was

more

obtuse and the lower border of the mandible more steeply inclined. He

further found no significant difference between the two samples in the

mean length of the ramus from articulare to gonion, nor the mean

length of the body of mandible from gonion to gnathion and also no

significant difference in the angular relationship between the horizontal

68

planes, anterior cranial base, Frankfort, palatal and occlusal planes.

Horowitz et al. (1969) undertook a study of lateral cephalograms

of 52 subjects (30 males and 32 females), 17 years of age or older, who

satisfied these criteria:

a) Lower portion of the face was prominent.

b) The presence of class III angle malocclusion, 36 individuals

showing deep bite and the rest anterior open bite.

The sample was compared with 30 untreated class I (angle)

occlusion subjects. He concluded that a high negative difference was

observed between the mandibular and maxillary apical bases (ANB).

The relationship of the mandibular apical base and mandibular body to

the cranium was greater m the prognathism subjects, indicating a more

forward positioning of the entire mandible (SNB). The mandibular

ramus position relative to the cranial base was smaller in the class III

group, reflecting forward positioning of the mandible relative to the

cranium (saddle angle). The relation of the ramus and body of the

mandible (the gonial angle) was largest in the open bite group and

intermediate in the deep bite group. The anterior portion of the

mandible was larger in prognathism groups. The position of maxilla

showed no difference (SNA). Maxillary length was smaller in

prognathism groups. Both anterior cranial base and the posterior

cranial base were shorter. The posterior face height was shorter in

prognathism groups, but there was no difference in anterior face height

in the deep bite and control groups, while it was significantly longer in

the open bite group.

69

Sassouni (1969) found that the class III skeletal relationship

could be associated with the characteristics of two types of vertical

disproportions (the skeletal deep bite and open bite). The constitution

of this skeletal type may be due to a dimensional or a positional

imbalance or both, and each type has its own characteristic features.

Class III skeletal type due to position deviation had the

characteristics of open bite and deep bite types. In common with deep

bite, it had small cranial base angle which brings the glenoid fossa and

therefore the condyles anteriorly relative to sella turcica. The mandible

was typical of the open bite of large gonial angle. The palate was

tipped upwards at PNS and downward at ANS which brings the

maxillary molar to the higher level. The end result of this set was

maxillary retrusion, mandibular protrusion, or both.

Class III skeletal type due to dimensional deviation which could

be either micromaxilla or macromandible. Micromaxilla had a short

constricted palate transversally, with crowding of the maxillary dental

arch. It showed impaction, the congenital absence of some teeth or

ectopic eruption of molars and a narrow nasal aperture.

Macromandible was due to the excessive length of mandible that might

be located at the condyles, the ramus, or the corpus. Seldom was the

mandible excessive in anteroposterior length without the breadth being

large. The chin was pointed and there was a long styloid process.

Dietrich (1970) studied a sample of 172 untreated skeletal class

III cases who had negative ANB angle, compared to 111 untreated

skeletal class I cases and divided it into three groups: deciduous, mixed

70

and permanent dentition. The age ranged from 3 to 17 years. The

results showed that the class III skeletal relation can be presented as

follows: mandibular prognathism cases which are characterized by an

SN A angle within the average normal range and an SNB angle greater

than the mean value. The saddle angle was significantly smaller in all

age groups with mandibular prognathism. The Y-axis angle was

significantly smaller in all age groups with mandibular prognathism.

The angle formed by the maxillary and mandibular planes was

significantly smaller only in the deciduous dentition group of

mandibular prognathism. The gonial angle was enlarged to a

significant degree only in the permanent dentition group of mandibular

prognathism. The lower incisors were significantly retruded in the

mixed and permanent dentition groups of mandibular prognathism

while the upper incisors were protruded. The length of the body of the

mandible, expressed by the linear measurement Gn-Go, was slightly

greater in the mandibular prognathism groups, without exhibiting a

statistically significant difference.

Maxillary retrognathism cases were characterized by an SN A

angle smaller than the mean value of the corresponding control group

and an SNB angle within the average normal range. The angle formed

by the maxillary and mandibular planes was significantly enlarged

only in the permanent dentition group. The gonial angle was

significantly enlarged in the mixed and in the permanent dentition

group. The lower incisors were significantly retruded in all groups of

maxillary retrognathism. The length of the maxilla, expressed by linear

71

measurement A-PNS was significantly reduced in all age groups of

maxillary retrognathism.

Ahlgren (1970) carried out study on a sample of 12 male and

female patients having angle class III malocclusion. The mean age was

17.8 (14-22 years old). All had full records including casts, lateral

cephalograms and electromyograms.

The cephalometric measurements showed distinct skeletal class III

relationship features, indicated by a negative ANB angle. The

explanation of the skeletal class III pattern lay both a protruded

mandible, indicated by an abnormal high value of the SNB, and a

retruded maxilla, indicated by a small SNA. Another significantly

different value was the gonion angle. The dental values indicated that

the lower incisors were retruded while the upper incisors tended to be

protruded.

Jacobson et al. (1974) carried out a study on pre-treatment lateral

cephalometric radiographs of 149 patients with class III malocclusion,

the sample comprised of sixty six adults, and eighty three children,

males and females (age range 6 to 16 years) and those films were

compared to 112 males and females with a normal occlusion (age

range 6 to 16 years). They found that the most significant difference

between adult sample of class III and normal occlusion was the ANB

angle, which may be attributed principally to the class III mandible

being more prognathic. Also contributing to this difference was the

shorter anterior cranial base in class III mal occlusion which in turn

tends to effect a relative maxillary deficiency. A further contributory

72

factor toward the class III skeletal relationship was a more obtuse

gonial angle, associated with a straight line morphology while the

glenoid fossa was located forward. They also found the differences in

the dental parameters appeared to have a compensatory response. They

concluded the differences comparing craniofacial and dental patterns

between child and adult class III skeletal relationship as follows: As

growth in class III malocclusion carried point B forward, the ANB

angle was increased, the lower incisors became upright, and the upper

incisors procline. Little effective growth rotation appeared to take

place, since the mandibular plane did not change significantly. Sexual

dimorphism was mainly reflected in the larger male class III mandible.

Although the craniofacial proportions of male and female class III

cases were similar, females tended to have a slightly more divergent

type of pattern.

Williams and Andreson (1986) did a cephalometric study on a

group of 24 (13 girls, 11 boys) class III skeletal relationship children

with an average age of 11 years (ranging 9 years to 12 years) who at

the cessation of growth (confirmed on hand/wrist films), exhibited a

sagittal jaw relationship judged by Wits analysis to be less than 4.mm.

The control group consisted of 33 children (16 boys, 17 girls) with

average age of 11 years (range 10 years to 11 years). They identified

the following characteristics in the growing child that could indicate

development of class III skeletal relationship: a reduction in maxillary

length and anteroposterior position relative to point sella were observed

in class III material whereas vertical dimension showed no significant

73

difference in class I material, neither anteriorly nor posteriorly.

The length of the mandible revealed that on average no difference

existed between the two groups. The sagittal position of the points

pogonion and B were placed more anteriorly and the distance

indicating sagittal position of the glenoid fossa relative to sella was

reduced in class III group. There was no significant difference in ramus

height between Group I and III. The ratio between maxillary and

mandibular lengths was reduced in class III material. On average the

Wits analysis for class III group was greatly reduced.

Guyer et al. (1986) conducted a cephalometric study of 143 (72

males, 71 females) class III malocclusion compared to 128 class I

controls (64 males, 64 females). The age range from 5-15 years. They

found that class III can be identified by various combination of skeletal

and dental components. Simple maxillary retrusion was found in 25 %

of the total sample, while mandibular protrusion, which was cited as

the major skeletal aberration in individuals with class III malocclusion,

was found in only 18.7% of the total sample. A combination of

maxillary retrusion and mandibular protrusion was found in 22.2 % of

this sample. 41 % of this entire sample had long lower face height.

They also found that the average characteristics of class III subjects

were as follows: the posterior cranial base length, was longer. The

effective length of class III maxilla was short while the position was

generally retrusive. The sagittal mandibular skeletal position was

prognathic, while the length was long.

The gonial angle was more obtuse. The mandibular plane angle

74

tended to be greater. There was greater vertical lower face height in

class Ill. Maxillary incisors were significantly protrusive and

mandibular incisors were retroclined.

Hashim and Sarhan (1993) conducted a study on a random

sample of 150 British school children age 9-12 years. Out of the 150

children, 27 lateral radiographs, 12 girls and 15 boys average age 10.5

years were selected on basis of an angle ANB < 10 indicating class III

skeletal relationship. The 27 subjects were further divided on the basis

of the angle SNB as having either a normal or protruded mandible.

They found that for the antero posterior position of the maxilla, the

value of SN A was less than the mean for normal mandible, while for

protruded mandible it was more than the mean. The cranial base angle

NSA for normal mandible approached the mean value but for

protruded mandible it decreased. The gonial angle had no difference

between the two groups. The Y-axis angle was decreased in patients

with protruded mandibles than normal. SN-mandibular plane angle was

increased for subjects with normal mandibles and decreased for

subjects with protruded mandibles. SN occlusal plane angle was within

normal range for normal mandible while it was decreased for protruded

mandible. Subjects with normal, mandible had a shorter distance for

Ar-S than those with protruded mandible. The position of upper

incisors to A-pog line was protruded for normal mandible, while those

with a protruded mandible had normally positioned upper incisors.

75

2.7 Cephalometric studies in Saudi Arabia.

The Saudi Arabian population living in the Arabian Peninsula

had not been previously exposed to any extensive cephalometric

research to determine the degree of skeletal discrepancy. However, the

literature revealed that a few studies were conducted to assess facial

types and malocclusion.

Jones (1987) conducted a study on 132 subjects of consecutive

patients attending to orthodontic clinic in Riyadh. The age ranges

between 5 and 32 years for the females, and between 6 and 29 years of

age for males. They were examined for occlusal relationship and

crowding. The dental malocclusion were found to be class I, 53.8 %;

class Il division 1, 28.8%; class Il division 2, 4.5%; and class Ill,

12.9%. The survey of crowding was 67.4 %. In the same paper another

study was reported on a subgroup of 69 patients from the above 132

subjects who underwent orthodontic treatment. This was undertaken to

assess the skeletal discrepancy by analyzing their cephalometric

radiographs. He found the skeletal pattern as follows: class I skeletal

relationship was 46.6%, class II skeletal 27.5 % and class III skeletal

26.1 %. In addition to these interesting findings, he also found that in

comparison with other populations there was a tendency for

bimaxillary proclination, dento alveolar compensation and greater

proportion of class III than in Western communities.

Shalhoub et al. (1987) carried out a study for adult Saudi

Arabians to derive cephalometric norms for orthognathic surgery.

Lateral cephalometric radiographs were taken for 48 Saudi adult

76

patients (24 males, 24 females) with an age range from 20 to 46 years.

All showed normal dental relationship, with no severe antero posterior,

vertical, or transverse skeletal discrepancies. Angular and linear

measurements were recorded and compared to a similar sample of

North American caucasians. They established cephalometric values for

male and female Saudi and the differences between them and North

American sample. The differences indicated that the Saudi female

demonstrates a protrusive maxilla, midfacial prominence, and a short

mandibular length and greater forward rotation of the mandible and

lesser amount of overbite while the Saudi male had a more protrusive

midface and lesser amount of overbite.

Sarhan and Nashashibi (1988) carried out a study on a randomly

selected sample of 50 Saudi boys aged from 9 to 12 years with no

orthodontic treatment to derive cephalometric .standards for Saudi

boys. Lateral skull radiographs had been taken with teeth in occlusion.

The Saudi sample was compared with a British sample aged 9-12

years. They found that there was a difference between the two samples.

Generally, the Saudi sample demonstrated a slightly prognathic face,

more protrusive upper and lower incisors, and low gonia I and saddle

angles.

Toms (1989) studied records of 500 consecutive Saudi Arabian

patients with an age range from 10-21 years (mean age 13.7 years)

referred for orthodontic treatment. The subjects were examined

clinically and radiographically for skeletal discrepancy to determine

the percentage of class III malocclusion. He found that class III

77

malocclusion represented 9.4 % of the whole sample. Mandibular

prognathism was a commoner feature of class III skeletal discrepancy

than maxillary retrognathism. When investigating the characteristic

features of class III malocclusion compared to those of the control

groups, the saddle angle was reduced, maxillary length was small and

the maxillary and mandibular plane angles also reduced. On the other

hand, the gonial angle, anterior and posterior facial heights and

mandibular length were significantly large. He also found that the

upper and lower incisors exhibited a marked degree of dento alveolar

compensation for the underlying skeletal relation.

Nashashibi et al. (1990) investigated the cephalometric standards

of Saudi boys based on Steiner's analysis. The sample consisted of 55

healthy Saudi boys who were selected from different schools in

Riyadh, with a mean age of 12 years. The criteria for sample selection

was made as the basis of normal occlusion, balanced and pleasing

profiles with facial symmetry. Lateral skull radiographs were taken and

measured. The results were compared to similar studies conducted on

other ethnic groups. They found that the Saudi boys differed from

other racial and ethnic groups in some skeletal and dental

measurements. Generally, the Saudi boys revealed a more protrusive

maxilla and double dental protrusion.

It is clear that the few studies conducted in Saudi Arabia (lones,

1987; Shalhoub et al., 1987; Toms, 1989) generally showed that there

was a tendency for Saudis to have a degree of bimaxillary protrusion,

increased lower facial height with more incidence of class III

78

malocclusion .

2.8 Incidence of skeletal discrepancy.

Searching the literature shows very few studies reported the

incidence of skeletal discrepancy in a population. On the other hand

numerous studies have been carried out to show the incidence of

malocclusion (Gardiner, 1982; Farawana, 1987). Generally, an

approximation of the incidence of skeletal discrepancy may be

obtained from the incidence of dental malocclusion, which is the

occlusion roughly associated with skeletal relationship, even though

the figures obtained have shown little agreement with each other. This

may be due to various factors including differences in the criteria of

selection, methods of assessment, ages and size of sample (most

methods of assessment were based upon Angle's classification normal

and malocclusion). Some of the surveys that have been carried out are

listed in Table 2.8.1. These surveys showed the incidence of dental mal

occlusion in various Caucasian samples.

When comparing the studies with each other, a wide variation was

noted in the various types of malocclusion. For class I mal occlusion

the variation ranged from 93.5 % (Gardiner, 1956) to 25.1 %, (Goose

et al., 1957), whereas, for class II malocclusion from 8.0% (Gardiner,

1956) to 35.0% (Luffingham and Campbell, 1974), and for class III

malocclusion from 0.5% (Brehm and Jackson, 1961) to 12.9% (Jones,

1987).

79

Table 2.8.1: Survey of the incidence of malocclusion based on angle’s and incisor classification

Investigators Date Country Sample Age Normal Class Class Class

Number Group I II III (Yrs)

Sclare 1945 England 334 12 40.5% 30.0% 27.0% 1.0%

Bjork 1947 Sweden 322 12 26.4% 51.8% 18.9% 2.8%

Massler and Frankel 1951 USA 2,758 14-18 21.1% 50.0% 20.0% 9.0%

Gardiner 1956 England 1,000 6-15 25.0% 66.0% 8.0% 1.0%

Goose, Thompson and Winter 1957 England 935 11-12 55.3% 25.1 % 15.7% 3.7%

Haralabakis 1957 Greece 592 19-30 37.9% 36.3% 23.1% 2.5%

Hill, Blayney and Wolf 1959 USA 1,888 12-14 52.6% 33.5% 12.75% 1.1%

Brehrn and Jackson 1961 USA 6,328 6-17 16.6% 60.1 % 22.8% 0.5%

Ernrich, Brodie and Blayney 1965 USA 13,475 12-14 54.0% 30.0% 15.0% 1.0%

Haynes 1970 England 1,185 11-12 26.85% 50.3% 19.5% 2.5%

Luffingham and Campbell 1974 Scotland 269 14 - 57.0% 35.0% 8.0%

Gardiner 1982 Libya 479 10-12 - 77.0% 18.0% 5.0%

Farawana 1987 Iraq 200 6-24 - 59.6% 29.6% 10.8%

Jones 1987 Riyadh,

KSA 132 5-32 - 53.8% 33.3% 12.9%

80

It can be observed from the previous table (Table 2.8.1). Saudi

Arabian sample had the highest reported incidence of class III

malocclusion among all the samples. The highest reported value was 10.8

% and the lowest was 0.5 %, whereas, for the Saudi sample, it was 12.9%.

In case of class II malocclusion, the Saudi samples had 33.3 % (J ones,

1987) whereas, for Scots had 35.0 %. In case of class I malocclusion, the

Saudi sample had 53.8% and the English had 66.0% (Gardiner, 1956)

Another search through the literature was done to identify the

incidence of the skeletal discrepancy and its distribution among

Caucasians. It showed unfortunately that very few studies were conducted

to report the incidence of skeletal discrepancy. The findings of the

available literature were summarized in Table 2.8.2.

Walther (1960) carried out a research project which consisted of

random sample of 1000 children selected according to the following

criteria.

1. The age ranged between 11 and 13 years

2. They all came from secondary schools in East Anglia, UK.

3. One third of the children were taken from each school.

81

Table 2.8.1: Survey of the incidence of skeletal discrepancy classification

Investigators Date Country Sample

Number

Age

Group

(Yrs)

Skeletal

I

Skeletal

II

Skeletal

III

Walther 1960 England 1,000 11-13 35.6% 53.3% 11.1%

Foster and Day 1974 England 1,000 11-12 40.8% 53.8% 5.4%

Luffingham and Campbell 1974 Scotland 269 14 55.0% 29.0% 16.0%

Salvicek, Schadldauer and Schrangl 1983 Austria 2,275 Adult 37.2% 51.8% 11.1%

Farawana 1987 Iraq 200 6-24 74.5% 13.0% 10.0%

Jones 1987

Riyadh

Saudi

Arabia

69 5-32 46.4% 27.5% 26.1%

82

The study was conducted to find out the causes and effects of

malocclusion. By the clinical assessment of skeletal relation and by using

Ballard's method, he found that out of the 1000 cases: 35.6% had class I

skeletal relationship; 53.2 % skeletal Il relationship; whereas, skeletal III

was 11.1 %.

Foster and Day (1974) did a study on 1000 Shropshire children,

aged 11 to 12 years of age, with the objective of assessing some occlusal

features and the need for orthodontic treatment. The children examined

were first year pupils in secondary school, with equal number of girls and

boys. They found that the skeletal relationship as an etiological factor

which was assessed clinically by Ballard method to be: 40.8% having class

I; 53.8 % class II: and only 5.4 % class III.

Luffingham and Campbell (1974) examined 269 children of whom

127 were male and 142 female. The sample involved were all secondary

school students with a mean age of 14 years. The antero-posterior jaw

relationship was assessed clinically. The patients were viewed in profile

with the Frankfort plane horizontal and points A and B were palpated.

They found that skeletal class I comprised 55 %, skeletal class II, 29% and

skeletal class III, 16%.

Farawana (1987) studied 200 persons attending the Orthodontic

Department at the College of Dentistry (Baghdad), to determine the

features of mal occlusion among the Iraqi population. The skeletal relation

was assessed clinically, based on Broadbent's classification and

radiographically according to the ANB angle (a larger angle than normal

would indicate a class II skeletal relation, while a negative ANB would

83

indicate a class III skeletal relationship). She found that the predominant

skeletal relationship in the Iraqi patients was class I. It formed 74.5 %,

while class II formed only 13 % and class III only 10% of the sample.

Jones (1987) conducted a study on two separate samples of patients

attending orthodontic clinic in Riyadh. The age ranged from 5-32 years for

females and between 6 and 29 years for males. They were examined for

occlusal relation, and crowding. In the same paper another study was

reported on a subgroup of 69 patients offered treatment from the above 132

subjects to assess skeletal discrepancy using cephalometric radiographs. He

found that the skeletal pattern were as follows: class I skeletal was 46.4 %,

class II skeletal 27.5 % and class III skeletal 26.1 %.

However, this study was based on patients selected for orthodontic

treatment so it would be unwise to extrapolate this figure to the whole of

the Saudi population in view of the biased nature of the sample and its

small number (J ones, 1987).

84

3.0 STATEMENT OF THE PROBLEM AND PURPOSE OF THE STUDY

85

3.0 Statement of the problem and purpose of the study.

Skeletal discrepancies can lead to limitation for orthodontic

treatment. For proper diagnosis and treatment planning, such

discrepancies need to be known for each racial group of the human

population. The skeletal characteristics and classification in some ethnic

groups were documented, such as Chinese by Chan (1972), North

American Whites by Riolo et al. (1974), Negro by Fonseca and Klein

(1978) and British Caucasians by Bhatia and Leighton (1993).

In Saudi Arabia, the classification and characterization of skeletal

discrepancies are still not well covered. Although there have been few

studies (Jones, 1987; Toms, 1989) but these studies lacked randomness

and an adequate sample.

It was clear that there was a great need to conduct a study to

investigate in more detail the characteristic features of the various skeletal

classes in Saudi Arabia.

3.1 The Aims of the Present Study.

1. To investigate the various types of skeletal classes in a group of

female school children in Saudi Arabia.

86

2. To investigate the cephalometric skeleto-dental characteristic

features of class II and class III skeletal relationship compared to

class I.

3. To compare the cephalometric skeleto-dental results of class I of

the Saudi sample to the established Caucasian cephalometric

standards.

In achieving the aims, the following hypotheses will be

subjected for testing.

A. As Saudi Arabian population belongs to Caucasian, then they

should have similar skeleto-dental characteristics.

B. The skeletal discrepancies of class II and class III skeletal

relationship were attributed mainly to a positional and/or

dimensional cause.

87

4.0 Materials and Methods

88

4.0 Materials and Methods.

4.1 Materials.

The sample used in the present study consisted of 205 lateral skull

radiographs of Saudi female school children which were derived from a

large sample (5112 subjects) conducted in Jeddah, Saudi Arabia (Masoud

et al., 1994). The age range of the subjects were between 10-12 years with

a mean age of 11 years and a standard deviation of 1 year. Lateral skull

radiographs were taken with the head in natural head position.

4.1.1 Criteria for Sample Selection were as follows:

The following criteria were applied to select 205 cephalometric

readiograph from the large sample of 850 subjects.

1. The radiographs should be of high quality.

2. The first permanent molars should be in occlusion.

3. There should have been no previous orthodontic treatment.

4. There should be no cleft or craniofacial deformities.

5. The age of the individuals should be between 10 and 12 years old.

89

4.1.2 Tracing Technique.

The radiographs were traced under standardized procedure using sharp 3H

lead pencil on fine acetate tracing papers. This was performed in a

darkened room to obtain maximum contrast and to facilitate landmark

identification. Bilateral structures giving double images e.g. gonion and

articulare, the mid-point was chosen.

4.1.2.1 Cephalometric Landmarks.

The following landmarks were identified and recorded in sequence.

Planes and lines were drawn, then angular, linear, and proportional

measurements were obtained.

4.1.2.1A Definition of the Landmarks

Landmarks Abbreviations Description

1) Sella S The mid-point of the sella turcica

2) Porion Po The upper most outermost point on

the bony external auditory meatus

3) Basion Ba The most posterior inferior point on

the Clivus. It lies on the anterior

margin of foramen magnum

90

Landmarks Abbreviation Description

4) Hinge Axis HA The center of the condyle

5)

Pterygoid

point

Pt

A point is located on the

posterior-superior border of

the pterygo-maxillary fissure.

It identifies the place of

emergence (foramen

rotundum) of the maxillary

nerve from the cranial base.

6) Nasion N The most anterior point on the

fronto-nasal suture

7)

Orbitale

Or

The most inferior anterior

point on the margin of the orbit

8) Anterior nasal

spine ANS

The tip of the anterior nasal

spine

9) Posterior nasal PNS The tip of the posterior nasal

spine spine

10)

Point-A

A

The most posterior point on

the profile of the maxilla

between the anterior nasal

spine and alveolar crest

11)

Point-B

B

The most posterior point on

the profile of the mandible

between the chin point and

alveolar crest

12) Reversal Zone RZ It is the reversal zone

between two growth fields

where the concave surface

contour becomes convex

(Enlow 1990)

91


13) Pogonion Pog The most anterior point on the

bony chin

14) Menton Me

The lowest point on the lower

border of the mandibular

symphysis

15) Posterior

ramus PRM2 The most prominent posterior

Point-2 superior point at the angle

of the mandible on the ramus

16) Mandibular base MBI The most inferior point on the

Point-l lower border of the mandible

behind the antigonial notch

17)

Articulare

Ar

The point of intersection

between the posterior border of the mandibular condyle and

lower border of the cranial

base

18) Upper Incisor UIE The tip of the most prominent

edge upper incisor crown

19) Upper Incisor UIA The root apex of the most

Apex prominent upper incisor

20) Lower Incisor LIE The tip of the most prominent

Edge

Lower Incisor

lower incisor crown

21)

LIA

The root apex of the most

prominent lower incisor

22) Occlusal Point Oc The mid-point in the occlusal

space between: the upper and

lower first premolars

92

These points are illustrated in Figure 10.


23) Upper Molar UDC The posterior contact (height

Distal Contact of contour) of the maxillary

Point. first

molar

24) Lower Molar LDC The posterior contact point of

Distal Contact the mandibular first molar

Point

25) Upper Molar UDR Distal buccal root of the

Distal Root maxillary first molar

26) Lower Molar

Distal Root LDR

Distal root of the mandibular

first molar

93

Figure 10: Illustration of Cephalometric landmarks

94

4.1.3 Digitization

The identified landmarks were digitized in a predetermined sequence

using digitizer linked to Mackintosh SE computer.

Figure 11. Illustration of the computer and the digitizer used.

Each radiograph was digitized by the investigator. The digitized

points were stored as X and Y coordinates in the computer memory. From

these coordinated new landmarks, planes and lines were derived

automatically and plotted on the monitor. From these, angular and linear

measurements can be calculated and presented for analysis. In addition to

the previous landmarks, new constructed landmarks planes and lines were

used in the present study.

95

4.1.3.1 Constructed landmarks

Gnathion Gn The most anterior inferior point on the

mandibular symphysis

Gonion Go The most posterior inferior point on

the angle of the mandible

Condylion Co The most superior posterior point of

the mandibular condyle

The above constructed landmarks are illustrated in Figure 12.

Figure 12: Illustration of constructed cephalometric landmarks

96

4.1.3.2 Cephalometric Planes and Lines.

From the coordinates, horizontal and vertical planes and lines were

constructed.

4.1.3.2.A The Horizontal Planes.

1) Sella-Nasion Plane SN A plane joining sella to nasion

and represented by the anterior

cranial base

2) Frankfort Horizontal FH This plane passes through points

porion and orbitale

3) Occlusal Plane Occ A plane passes through the

occlusion of the premolars or

deciduous molars and first and

permanent molars

4) Mandibular Plane MP It is defined by two ways: A

plane joining gonion to menton

and a plane joining gonion to

gnathion.

MP1 = Go - Gn

MP2 = Go - Me

The above horizontal planes are illustrated in Figure 13.

4.1.3.2.B The Vertical Planes and Lines

1) The Facial Plane Fp A plane joining the nasion pogonion

and used to assess the

facial profile

2) Y-Axis Plane Y-axis plane joining sella to gnathion

97

Figure 13: Illustration of horizontal cephalometric planes

98

3) Facial Axis plane F-axis A plane joining pterygoid gnathion

4) Ramal Plane Rm A plane joining A point to B point

5) A-B Plane A-B A plane joining A point to B point

The above vertical planes and lines are illustrated in Figure 14.

4.1.3.3 Angular Measurements

From the digitized points, 18 angular measurements were obtained.

These were:

1) SNA angle

SNA = the angle subtended by the SN plane and point

A.

2) SNB angle

SNB = the angle subtended by SN plane and point B.

3) ANB angle

ANB = the difference between angles SNA and SNB.

4) Angle of convexity

A-N- Pog = the angle subtended between facial plane and

the line joining points A and N.

5) Facial angle

FH/Fp = the inferior inside angle subtended by the

Facial plane and Frankfort plane.

6) AB plane angle

Fp/AB = the angle subtended by the line joining

points A and B and the facial plane.

99

Figure 14: Illustration of vertical cephalometric planes

100

7) Saddle angle

N-S-Ar = The angle subtended by the SN plane and

the line joining sella to articulare.

8) Gonial angle

Ar-Go-Me = The angle subtended by the Ramal plane

and mandibular plane.

9) SN/Occ = The angle subtended by the SN plane and

occlusal plane.

10) SN/MP1 = The angle subtended by the SN plane and

mandibular plane (Go-Gn).

11) FH/Occ = The angle subtended by the Frankfort

plane and occlusal plane.

12) FH/MP2 = The angle subtended by the Frankfort

plane and mandibular plane (Go-Me)

13) Y-Axis angle

FH/Y-Axis = The angle subtended by the Frankfort

plane and Y-axis plane.

14) Facial-Axis angle

F-Axis/NBa The angle subtended by the F- Axis plane

and the line joining points N and Ba.

15) Lower incisor to MP2 angle

LIA-LIE/MP2 = The angle between the long axis of the

lower incisor and the mandibular plane

(Go-Me).

16) Upper incisor to NA angle

UIA-UIE/NA = The acute angle formed by the long axis

of the upper incisor and the line N A.

17) Lower incisor to NB angle

LIE- LIA/NB = The acute angle formed by the long axis

of the upper and lower incisors.

101

18) Interincisal angle

LIE-LIA/UIE-UIA = The angle formed by the long axes of the

upper and lower incisors.

The above angular measurement is illustrated in Figures 15, 16, 17.

4.1.3.4 Linear Measurements

Also from the digitized points 17 linear measurements were

obtained:

1) Point A to Nasion Perpendicular

A/N ┴ FH = The horizontal distance in mm from point

A to the vertical line extended inferiorly

from Nasion perpendicular to the

Frankfort plane.

2) Pogonion to Nasion Perpendicular

Pog/N ┴ FH = The horizontal distance in mm from

Pogonion to the vertical line extended

inferiorly from nasion perpendicular to

the Frankfort plane.

3) Mid-facial length

Co - A = The horizontal distance in mm from

condylion to point A.

4) Mandibular length

Co - Gn = The distance in mm from condylion to

Gnathion.

5) Mandibular body length

Go - Me = A horizontal distance in mm from Gonion

to Menton.

102

Figure 15: Illustration of angular measurements of anteroposterior skeletal

relationship

103

Figure 16: Illustration of angular measurements of vertical skeletal

relationships

104

Figure 17: Illustration of angular measurements of dental relationships

105

6) Pog/NB = The horizontal distance in mm from

Pog to line joining N, B points.

7) Anterior cranial base

N - S =

The horizontal distance in mm from

Nasion to Sella.

8) Posterior cranial base

S - Ar =

The distance in mm from Sella to

Articulare.

9) Ramus height

Ar - Go =

The distance in mm from

Articulare to Gonion.

10) Posterior facial height

S - Go =

The distance in mm from Sella to

Gonion.

11) Total anterior facial height

N - Me=

The distance in mm from Nasion to

Menton.

12) Lower anterior facial height

ANS - Me =

The distance in mm from Anterior

nasal spine to Menton.

13) Upper incisor to NA

UIE/NA =


the tip of the upper to the NA line.

14) Lower incisor to NB

LIE/NB =


the tip of the lower incisor to the

line NB.

15) Upper incisor A-Pog line

UIE/A Pog =

The horizontal distance in mm

from the tip of the upper incisor

to theline A-pog.

106

16) Upper incisor to A ┴ FH

UIE/A ┴ FH = The horizontal distance in mm

from facial surface of the upper

incisor to the vertical line passed

through point A parallel to Nasion

perpendicular to the Frankfort

plane.

17) Lower incisor to A-Pog

LIE/A Pog = The horizontal distance in mm from

facial surface of the lower incisor to

the line A-Pog.

The above linear measurements are illustrated in Figures 18 and 19

4.1.3.5 Proportional measurements

Only two proportional measurements were obtained from the digitized

points:

1) S - Go/IN - Me = The posterior facial height as

a percentage of total anterior

facial height.

2) ANS - Me/N -Me = The lower anterior facial height

as a percentage of total anterior

facial height.

107

Figure 18: Illustration of linear measurements of skeletal relationship

108

Figure 19: Illustration of linear measurements of dental relationship

109

4.2 Assessment of Method Error

For any set of experiments, performing measurement is not enough. It

is essential to know if the measurement taken is good enough for achieving

the required aims (Barford, 1990).

Measurement errors may be systematic (errors associated with the

particular instrument or technique of measurement being used) or random

(errors produced by a large number of unpredictable and unknown

variations in the experimental situation).

There are different sources of the systematic error which may arise in

obtaining lateral skull radiographs if the geometry of the system varies and

no compensation is made. If measurements from two different studies are

compared; then it is assumed incorrectly that the magnifications are the

same, when two series of radiographs are measured by different persons

who have different concepts of a particular landmark (Houston, 1983).

Even when all systematic errors have either been eliminated or

corrected for, identical measurements were not obtained for repeated sets

of readings, the errors that remain were called random error (Young, 1962)

or experimental error.

110

The random error arise as a result of variations in positioning of the

patient in the cephalostat. Variations in film density and sharpness also lead

to random error. The greatest source of the random errors is difficulty in

identifying a particular landmark or imprecision in its definition (Houston,

1983).

4.2.1 Assessment of cephalometric error.

For the accuracy of cephalometric measurements, the two main

sources of error; the systematic or bias, and random errors should be

controlled and/or assessed .

. 4.2.1.A Systematic error.

A radiograph, being a two dimensional representation of a three

dimensional object, is subject to distortion. And because the rays are not

parallel diverging from a small source onto the film is subjected to

enlargement.

The magnitude of enlargement depends on the relative distance

between the film, target and object. The closer the object to the x-ray

source and/or the further the film is from the object the greater the

enlargement (Bergersen, 1980).

111

All radiographs utilized in this study were derived from a single

source with a fixed distance between the subject and the source of the x-

ray of 6 feet, and the same exposure being made by one machine.

The magnification factor was found to be 10.6% and calculated as

follows:

Actual measurement of ear rods = 8 mm

Radiographic measurements of the ear rods

a. If 9 mm closer to the film:

Measurement = 8.4 mm

Magnification - 0.4 x 100 - 5%

8

b. If 33.5 cm further away from the film:

Measurement = 9.3 mm

Magnification - 1.3 x 100 -16.2%

8

c. The midline magnification is

5 + 16.2 - 10.6%

2

The magnification factor 10.6% was entered into the computer to

compensate for enlargement of the linear measurements.

112

4.2.1.B Random error.

This error was evaluated as follows:

1. Intra-examiner: A total of 30 radiographs were randomly selected,

retraced and redigitized after a period of 6 weeks.

2. Inter-examiner: The same 30 radiographs retraced and redigitized by

the supervisor as a reference examiner within the same week. The

error was assessed by the double determination method of (Dahlberg,

1940) and coefficient of reliability (Guilford and Fruchter, 1984).

113

4.3 Assessing Skeletal Relationships

To differentiate between the different skeletal classes, I, II, and III, the

angle ANB (2.9° + 2.4°) of 11 years female as reported by Bhatia and

Leighton (1993) was utilized.

- Class I skeletal relationship = ANB > 0.5° < 5.3°

- Class II skeletal relationship = ANB > 5.3°

- Class III skeletal relationship = ANB < 0.5°

In this study, the class I skeletal relationship will be considered as

the control group.

114

4.4 Assessing the skeleto-dental characteristic features of

Class II and III groups.

The characteristic features of class II and class III skeletal

relationships were assessed by comparing them to class I group which was

considered as a control group.

The above mentioned 18 angular, 17 linear and 2 proportion

measurements (see section 4.1.3.3 - 4.1.3.5) were used for comparison.

115

4.5 Comparison of Saudi skeleto-dental characteristics to

established Cephalometric Standards

The values of skeleto-dental measurements obtained for class

I skeletal relationship (Control group) were compared to the

established cephalometric standards reported by Riolo et al. (1974)

for North Americans Caucasians, and Bhatia and Leighton (1993)

for British Caucasians. The previously mentioned 18 angular, 17

linear and 2 proportional parameters (see section 4.1.3.3 - 4.1.3.5)

were used for assessment and comparison between the different

skeletal classes.

116

4.6 Statistical Analysis of the Data.

The following descriptive and inferential statistical procedure were

used for data analysis.

4.6.1 Descriptive Analysis.

The following statistics were calculated for each measurement.

1. Mean

Mean - ∑ X

N

where ∑ X = the summation of the measurement

N = The number of subjects in the sample

2. Standard Deviation of the measurement

S.D. - √

N-1

3. Standard error of the mean

S.E.- √

117

4. Minimum

5. Maximum

4.6.2 Statistical Assessment of Method Error.

The method error was evaluated from the replicated

measurements (see section 4.2.1B).

4.6.2.1 Dalhberg's Method Error.

The most commonly used statistics in orthodontics to establish

random error of the method, strictly speaking reflect the errors of a

single measurement.

Dahlberg’s Formula - √

where d = difference between two readings

N = number of duplicants

This calculation was applied for both intra-examiner and inter-

examiner errors.

4.6.2.2 Coefficient of Reliability.

This statistic was computed to lend support to the various

description of the method error. A high correlation between the two

118

readings would be an indication of the sensitiveness of the method, and

correspond to a low error.

Coeficient of Reliability - 1 -

Se2 = Variance due to Random Error

St2 = Total Variance of the Measurement

This calculation was done for both intra-examiner and inter-

examiner sets.

4.6.3 Statistical comparison between the groups.

The student t-test was used to evaluate the significant difference

between the mean values of the two samples used in this study as

follows:

4.6.3.1 Comparison between Saudi control group and Saudi class

II and class III groups.

The student t-test was applied for comparison between the

control group (class I) and class II and class III skeletal relationship

in the following way:

t-value - x1 – x2 (Guilford, Fruchter,1984)

S.E. of Difference

119

S.E. of difference - S.D. of difference

√

S.E. of difference - √

N-1

Where X1 = mean of control group of Saudi sample

Where X2 = mean of class 11 or class III skeletal

relationship of Saudi sample

S.E. difference = the standard error of the difference between the

two means

d = difference between the two means

4.6.3.2 Comparison of control group of Saudi sample to

established cephalometric standards.

The t-test is applied to compare the control Saudi group with

Caucasian norms, Riolo et al. (1974) and Bhatia and Leighton (1993) in the

following way:

t-value -

√ (Swinscow. 1983, pp, 35)

S.D. - √

N – 1

120

Degree of freedom N-l

Where M = mean of established standards of Caucasian

population

X = mean of the Saudi sample

SD = standard deviation of the Saudi sample

N = number of the Saudi sample

4.6.3.3 The level of significance used for comparing the samples.

To identify the real difference between the means of the two

samples, the different levels of significance as described by Rowntree

(1991), were used.

1. P 0.05 (*). The significant level at 5 % i.e. five chances in l00,

and it is often called "significant".

2. P 0.01 (**). The significant level at 1 % i.e. one chance in

100, and it is often called "highly significant".

3. P 0.001 (***). The significant level at 0.1 % l.e. one

chance in 1000 and it is often called "very highly significant".

4. P = is accepted as being statistically significant at these three

levels.

121

5.0 RESULTS

122

5.0 Results

The results of this study will be presented in the following way.

5.1 The method error and reliability were covered in Tables from 5.1.1 to

5.1.3.

5.2 The classification of skeletal relation of the Saudi sample into

various classes and their distribution were presented in Table 5.2.1 and

Figure (19). From the above class I was considered as control group.

5.3 The results of comparing the skeleton-dental characteristics of class II

and class III skeletal relationships to class I group were presented in Tables

from 5.3.1.a.1 to 5.3.5.c.1.

5.4 The results of comparing skeleto-dental characteristics of Saudi

female class I skeletal relationship (control group) to established

cephalometric mean value of North American whites, (Riolo et al., 1974)

and British caucasian, (Bhatia and Leighton, 1993) were presented in

Tables from 5.4.l.a.1 to 5.4.5.c.l.

123

5.1 The method error and reliability of cephalometric

landmarks.

The method error was expressed by Dahlberg’s double determination

value and coefficient of reliability for 37 variables observed in repeated

recording of 30 radiographs. The results were presented in Table 5.1.1 for

angular measurements, Table 5.1.2 for the linear measurements and Table

5.1.3 for the proportional measurements.

It can be seen from the tables that the range of intra-examiner error

was from 0.4170 to 1.468

0 for angular measurements, from 0.404 mm to

0.711mm for linear measurements and from 0.447% to 0.531 % for

proportional measurements. The range of inter-examiner error was from

0.6980 to 2.912

0 for angular measurements, from 0.662 mm to 1.144 mm,

for linear measurements and from 0.768% to 0.877% as proportional

measurements.

The largest error was 1.468° and 1.432° for the variables FH/occ

and SN/occ respectively which could be due to the landmark identification.

Difficulty was encountered in the accurate location of the landmarks

involved in oc point, since the radiographs were of growing children and

the premolar had not fully erupted. As a result, a slight shift in the position

of this point will magnify the error involved. This is supported by the large

error of the inter-examiner 2.912° and 2.869°

124

respectively. It can also be seen that the intra-examiner error was high

for (inter incisal angle) 1.009°. And for (LIA-LIE/MP2) 0.989° and this

was supported by the large error of the inter-examiner 1.469° and 1.432°

respectively.

The coefficient of reliability for the measurement of SN/occ and

PH/occ was less than 0.9. This may indicate that this measurement

should be treated with suspicion (Houston, 1983).

125

5.1 The method error and reliability of cephalometric landmarks.

Table 5.1.1 The method error and coefficient of reliability of the intra examiner and

inter examiner for angular measurements of 18 variables in the skeleto dental

relationship of 30 repeated recordings. All readings in degrees.

Variables Intra Examiner Inter Examiner

Angular

Measurements

Dahlberg's

Method

Error

Coefficient

of

Reliability

Dahlberg's

Method

Error

Coefficient

of

Reliability

1. SNA 0.513 0.963 1.122 0.899

2. SNB 0.465 0.966 0.978 0.912

3. ANB 0.417 0.965 0.724 0.932

4. Angle of convexity 0.549 0.966 1.005 0.905

5. Facial angle 0.481 0.961 0.727 0.936

6. A-B plane angle 0.523 0.959 0.826 0.926

7. Saddle angle 0.554 0.965 1.136 0.902

8. Gonial angle 0.726 0.932 1.232 0.901

9. SN/Occ 1.432 0.895 2.869 0.546

10. SN/MP1 0.522 0.965 0.967 0.930

11. FH/Occ 1.468 0.894 2.912 0.513

12. FH/MP2 0.557 0.961 0.808 0.936

13. V-axis angle 0.476 0.962 0.698 0.939

14. Facial axia angle 0.443 0.967 0.752 0.940

15. LlA-LlE/MP2 0.989 0.922 1.432 0.896

16. UIA-UIE/NA 0.846 0.914 1.157 0.893

17. LlE-LlA/NB 0.795 0.937 1.472 0.885

18. Interincisal angle 1.009 0.909 1.469 0.896

126

5.1 The method error ••• (continued)


inter examiner for the linear measurements of 17 variables in the skeleto dental

relationship of 30


Linear

Measurements

Dahlberg's

Method

Error

Coefficient

of

Reliability

Dahlberg's

Method

Error

Coefficient

of

Reliability

1. A / N ┴ FH 0.519 0.963 1.144 0.892

2. Pog / N ┴ FH 0.588 0.966 1.484 0.885

3. Co - A 0.435 0.966 0.688 0.943

4. Co - Gn 0.451 0.967 0.945 0.917

5. Go - Me 0.662 0.953 1.121 0.892

6. N-S 0.476 0.965 0.830 0.929

7. S - Ar 0.494 0.965 0.878 0.932

8. Ar - Go 0.711 0.959 0.844 0.936

9. S - Go 0.562 0.964 0.816 0.941

10. N - Me 0.478 0.967 0.899 0.936

11. ANS - Me 0.454 0.966 0.856 0.931

12. UIE / NA 0.471 0.959 0.771 0.928

13. LIE / NB 0.404 0.966 0.669 0.939

14. UIE / A Pog 0.449 0.961 0.729 0.931

15. UIE / A ┴ FH 0.501 0.959 0.771 0.928

16. LIE/A Pog 0.422 0.963 0.662 0.938

17. Pog / NB 0.458 0.952 0.775 0.931

127

5.1 The method error… (continued)


inter examiner for proportional measurements of 2 variables in the skeleto dental

relationship of 30 repeated recordings. All readings in %.


Proportions

Dahlberg's

Method

Error

Coefficient

of

Reliability

Dahlberg's

Method

Error

Coefficient

of

Reliability

1. ANS – Me / N - Me 0.447 0.956 0.768 0.910

2. S – Go / N – Me 0.531 0.963 0.877 0.931

128

5.2 The skeletal classification of the 205 Saudi females based on

ANB angle, and their distribution

The frequency and percentage of skeletal classification of the saudi

females were presented in tabular form in Table 5.2.1, and graphically as

pie chart in Fig. 20. It is clear from the results that skeletal class I

constitutes the highest percentage (68.3 %), whereas, class II and class III

exhibited relatively similar percentage of 16.1 % and 15.6%, respectively.

Angle ANB of values 2.90+2.4

0 as reported by Bhatia and Leighton

(1993) was used to represent class I, any reading above that was considered

class II skeletal relationship and any reading below that was considered

class III skeletal relationship.

129

5.2 The skeletal classification of the 205 Saudi females based on ANB

angle and their distribution

Table 5.2.1 The frequency and percentage of the skeletal discrepancy of

205 Saudi females classified by the ANB angle based on the comparison to

ANB value of British white caucasian.

Figure 20 Pie chart of the frequency and percentage of the skeletal

discrepancy of 205 Saudi female classified by the ANB angle based on the

comparison to ANB value of British white caucasian.

Skeletal relationship

Frequency

Percent

Class I 140 68.3%

Class II 33 16.1%

Class III 32 15.6%

130

5.3 The skeleto dental characteristics of skeletal class II and class III

compared to class I skeletal relationship of Saudi females.

This part was divided into five sections:

5.3.1 Skeletal relationship

The results of the analysis of skeletal relationship were presented in

Tables from 5.3.1.a.l to 5.3.1.a.3 (antero-posterior dimension), and Tables

5.3.1.b.l to 5.3.1.b.13 (vertical relationship). It is clear from the tables that

there were significant differences between class II and class I skeletal

relationship, and also between class III and class I skeletal relationship in

anteroposterior dimension. For vertical relationship, there were no

significant difference for most of the comparison except for SN/MP1

SN/occ (class III), Y-axis angle and facial axis angle for both class II and

class III and ramus height in class II only.

5.3.2 Cranial base.

The results of the cranial base measurements were covered in Tables

5.3.2.1 to 5.3.2.3. It is clear that there were no significant differences

between all classes in both angular and linear measurements of the cranial

base.

131

5.3.3 Maxilla

The results of maxillary measurements were presented in Tables

5.3.3.1 to 5.3.3.3. These results showed that there were significant

differences between the skeletal class I, class II, and class III in both

angular and linear measurements. The level of significance in class II

compared to class I skeletal relationship was very high.

5.3.4 Mandible

The results of the mandibular measurements were presented in

Tables 5.3.4.1 to 5.3.4.6. It is obvious from the tables that there was

significant differences between skeletal class I and class II skeletal

relationship. Skeletal class III was compared to skeletal class I showed

no significant differences. Except one measurement (pog/N ┴ FH in

mm) showed a significant difference.

5.3.5 Dento alveolar relationship

The results of dento-alveolar relationship measurements were

presented in Tables 5.3.5.a.l to 5.3.5.a.4 (maxillary incisor position),

5.3.5.b.l to 5.3.5.b.4 (mandibular incisor position), and Tables 5.3.5.c.1

(maxillary mandibular inter-incisal angle). The maxillary incisor position,

132

or skeletal class II angulation were statistically significant when compared

to skeletal class I and class III. Mandibular incisor position and angulation

also showed significant differences between the three skeletal classes

except for LIE/A Pog (mm) when skeletal class II was compared to skeletal

class I. Inter-incisal angle, (Table 5.3.5.c.l) showed a statistical significant

difference when skeletal class II was compared to skeletal class I.

However, no statistical significant difference was observed between

skeletal class III and skeletal class I.

133

5.3 The skeleto dental characteristics of class II and class III

skeletal compared to class I skeletal relationship of Saudi

females.

5.3.1 The skeletal relationship

5.3.1.a Anteroposterior relationship

Table 5.3.1.a.l The mean and spread of measuring the ANB angle in

degrees recorded for class I, class II, class III skeletal relationship of

Saudi females. The t-value of the mean difference of (class I-class II) and

(class I-class III) is shown with its level of significance.

ANB dg Mean S.D. Min. Max. S.E.

Class I Group

(N = 140) 3.1 1.1 0.8 5.3 0.09

Class II Group

(N = 33) 7.0 1.5 5.5 11.1 0.27

Class III

Group

(N = 32)

-0.5 0.9 -2.9 0.4 0.16

t-value (Class I - Class II) = 13.2

Level of significance - ***

t-value (Class I - Class II =16.8


P ≤ 0.05 (*) significant

P ≤ 0.01 (**) highly significant

P ≤ 0.01 (***) very highly significant

N

S

= not significant

134

5.3 The skeleto dental characteristics… (continued)

5.3.1 The skeletal relationship… (continued)

5.3.1.a Anteroposterior relationship…(continued)

Table 5.3.1.a.2 The mean and spread of measuring A-B plane angle in

degrees recorded for class I, class II, class III skeletal relationship of Saudi

females. The t- value of the mean difference of (class I - class II) and (class

I - class III) is shown with its level of significance.

A - B Plane

Angle dg Mean S.D Min. Max. S.E.

Class I Group

(N = 140) -4.8 1.8 -0.5 -10.0 0.15

Class II Group

(N = 33) -9.8 2.5 -5.5 -7.5 0.45

Class III Group

(N = 23) 0.05 1.3 -3.9 2.7 0.2



t-value (Class I - Class III =13.9


Table 5.3.1.a.3 The mean and spread of measuring the angle of convexity

in degrees recorded for class I, class II, class III skeletal relationship of

Saudi females. The t- value of the mean difference of (class I - class II) and

(class I - class Ill) is shown with its level of significance.

Angle of

Convexity dg Mean S.D Min. Max. S.E.

Class I Group

(N = 140) 5.4 3.1 0.1 13.9 0.27

Class II Group

(N = 33) 14.5 3.6 8.6 24.5 0.62

Class III Group

(N = 32) -2.8 2.6 -8.5 3.20 0.39



t-value (Class I - Class III = 17.2


135



5.3.1.b Vertical relationship

Table 5.3.1.b.l The mean and spread of measuring the SN/MP1 angle in


Saudi females. The t- value of the mean difference of (class I -class II)

and (class I - class Ill) is shown with its level of significance.

Table 5.3.1.b.2 The mean and spread of measuring the SN/occ angle in


Saudi females. The t- value of the mean difference of (class I - class II)

and (class I - class III) is shown with its level of significance.

SN/MP1 dg Mean S.D Min. Max. S.E.

Class I Group

(N = 140) 35.8 5.1 23.7 51.4 0.43

Class II Group

(N = 33) 37.5 5.8 26.8 51.2 1.02

Class III Group

(N = 32) 33.6 5.1 18.3 42.7 0.91


Level of significance - NS


Level of significance - *

SN/Occ dg Mean S.D Min. Max. S.E.

Class I Group

(N = 140) 21.7 5.4 8.0 42.0 0.45

Class II Group

(N = 33) 21.7 5.4 8.0 42.0 0.45

Class III Group

(N = 32) 19.2 6.2 5.9 35.2 1.1





136


5.3.1 The skeletal relationship … (continued)

5.3.1.b Vertical relationship… (continued)

Table 5.3.1.b.3 The mean and spread of measuring Y-axis angle in degrees

recorded for class I, class II, class III skeletal relationship of Saudi females.

The t-value of the mean difference of (class I - class II) and (class I - class

III) is shown with its level of significance.

Table 5.3.1.b.4 The mean and spread of measuring the FH/occ angle in




FH/MP2 dg Mean S.D Min. Max. S.E.

Class I Group

(N = 140) 27.7 4.8 15.1 39.5 0.41

Class II Group

(N = 33) 29.5 5.9 20.3 40.6 1.02

Class III Group

(N = 32) 26.3 4.8 15.8 35.2 0.86





FH/Occ dg Mean S.D Min. Max. S.E.

Class I Group

(N = 140) 13.5 4.9 4.1 29.9 0.41

Class II Group

(N = 33) 13.6 5.4 3.7 23.2 0.94

Class III Group

(N = 32) 11.9 6.3 1.7 26.8 1.1





137








Table 5.3.1.b.6 The mean and spread of measuring facial axis angle in




Y Axis Angle

dg Mean S.D Min. Max. S.E.

Class I Group

(N = 140) 60.0 3.1 50.2 66.6 0.26

Class II Group

(N = 33) 61.4 3.8 54.1 69.8 0.67

Class III Group

(N = 32) 58.5 3.6 51.6 66.0 0.63





Facial axis

angle dg Mean S.D Min. Max. S.E.

Class I Group

(N = 140) 92.4 4.0 73 100.5 0.3

Class II Group

(N = 33) 94.5 2.4 88.3 100 0.4

Class III Group

(N = 32) 89.5 3.3 83.1 96.2 0.5





138

5.3 The skeleton dental characteristics… (continued)

5.3.1 The skeletal relationship ... (continued)

5.3.1.b Vertical relationship ... (continued)

Table 5.3.1.b.7 The mean and spread of measuring gonial angle in degrees




Gonial Angle


Class I Group

(N = 140) 126.8 6.4 110.9 143.2 0.54

Class II Group

(N = 33) 127.5 8.3 109.1 142.2 1.4

Class III Group

(N = 32) 127.9 6.7 113.4 142.9 1.2





139




Table 5.3.1.b.8 The mean and spread of measuring lower facial height in

mm recorded for class I, class II, class III skeletal relationship of Saudi

females. The t- value of the mean difference of (class I – class II) and (class


Table 5.3.1.b.9 The mean and spread of measuring anterior facial height in

mm recorded for class I, class II, class III skeletal relationship of Saudi



ANS - Me mm Mean S.D Min. Max. S.E.

Class I Group

(N = 140) 57.2 4.3 47.2 66.9 0.36

Class II Group

(N = 33) 57.6 4.2 48.9 66.7 0.74

Class III Group

(N = 32) 56.4 4.4 49.1 68.5 0.78





N - Me mm Mean S.D Min. Max. S.E.

Class I Group

(N = 140) 103.7 5.6 88.0 115.2 0.47

Class II Group

(N = 33) 103.5 6.4 92.3 117.5 1.1

Class III Group

(N = 32) lO1.8 5.5 93.8 119.4 0.98





140

5.3 The skeleto dental characteristics … (continued)


5.3.1.b Vertical relationship.. (Continued)

Table 5.3.1.b.10 The mean and spread of measuring posterior facial height

in mm recorded for class I, class II, class III skeletal relationship of Saudi



Table 5.3.1.b.11 The mean and spread of measuring ramus height in mm




S- Go mm Mean S.D Min. Max. S.E.

Class I Group

(N = 140) 65.6 5.0 49.6 79.6 0.42

Class II Group

(N = 33) 64.1 4.7 54.8 76.5 0.83

Class III Group

(N = 32) 65.6 5.1 57.0 82.6 0.91





Ramus Height

mm Mean S.D Min. Max. S.E.

Class I Group

(N = 140) 38.9 3.6 29.4 49.0 0.30

Class II Group

(N = 33) 37.4 4.0 30.0 49.08 0.70

Class III Group

(N = 32) 39.7 4.3 31.3 49.8 0.76





141



5.3.1.b Vertical relationship.. (Continued)

Table 5.3.1.b.12 The mean and spread of measuring ANS-Me/N-ME in

percentage recorded for class I, class II, class III skeletal relationship of


(class I - class III) is shown with its level of significance


percentage recorded for class I, class II, class III skeletal relationship of


(class I - class III) is shown with its level of significance

ANS-Me/N-

ME

%

Mean S.D Min. Max. S.E.

Class I Group

(N = 140) 55.1 2.3 49.6 63.1 0.19

Class II Group

(N = 33) 55.6 2.1 51.6 60.6 0.37

Class III Group

(N = 32) 55.4 2.2 50.8 61.1 0.45


Level of significance – NS



S-Go/N-Me % Mean S.D Min. Max. S.E.

Class I Group

(N = 140) 63.3 4.2 53.5 73.9 0.35

Class II Group

(N = 33) 62.0 4.7 51.9 71.4 0.83

Class III Group

(N = 32) 64.5 4.5 57.5 77.4 0.8





142


5.3.2 The cranial base

Table 5.3.2.1 The mean and spread of measuring S-N in mm recorded for

class I, class II, class III skeletal relationship of Saudi females. The t- value

of the mean difference of (class I - class II) and (class I - class III) is shown

with its level of significance

Table 5.3.2.2 The mean and spread of measuring S-Ar in mm recorded for




SS-N mm Mean S.D Min. Max. S.E.

Class I Group

(N = 140) 64.3 2.7 57.5 72.8 0.23

Class II Group

(N = 33) 64.2 2.4 55.6 69.7 0.47

Class III Group

(N = 32) 64.9 3.3 59.2 73.3 0.59





S-Ar mm Mean S.D Min. Max. S.E.

Class I Group

(N = 140) 29.8 2.9 23.3 39.4 0.24

Class II Group

(N = 33) 29.5 1.8 24.1 34.6 0.32

Class III Group

(N = 32) 29.8 2.6 25.4 36.5 0.50





143


5.3.2 The cranial base … (continued)

Table 5.3.2.3 The mean and spread of saddle angle in degrees recorded for




Saddle Angle


Class I Group

(N = 140) 123.5 5.3 105.2 139.1 0.45

Class II Group

(N = 33) 123.9 3.6 114.7 131.2 0.63

Class III Group

(N = 32) 123.3 3.3 113.2 132.4 0.58





144


5.3.3 The Maxilla

Table 5.3.3.1 The mean and spread of measuring SNA angle in degrees


The t- value of the mean difference of (class I - class II) and (class I - class

III) is shown with its level of significance

Table 5.3.3.2 The mean and spread of measuring A/N ┴ FH in mm




SNA dg Mean S.D Min. Max. S.E.

Class I Group

(N = 140) 80.8 3.7 71.3 92.3 0.31

Class II Group

(N = 33) 83.3 2.5 78.2 87.0 0.43

Class III Group

(N = 32) 78.6 4.2 70.1 91.8 0.75


Level of significance – ***


Level of significance - **

A/N ┴ FH mm Mean S.D Min. Max. S.E.

Class I Group

(N = 140) -1.9 3.2 -10.9 7.5 0.27

Class II Group

(N = 33) 0.3 2.4 4.7 3.8 0.41

Class III Group

(N = 32) -3.9 3.6 -11.8 6.4 0.64





145


5.3.3 The Maxilla … (continued)

Table 5.3.3.3 The mean and spread of measuring maxillary length in mm




Maxillary

Length mm Mean S.D Min. Max. S.E.

Class I Group

(N = 140) 74.9 4.4 50.4 85.5 0.38

Class II Group

(N = 33) 76.6 2.9 70.8 83.9 0.51

Class III Group

(N = 32) 72.4 5.4 50.0 81.6 0.97


Level of significance – **



146


5.3.4 The Mandible

Table 5.3.4.1 The mean and spread of measuring SNB angle recorded for




Table 5.3.4.2 The mean and spread of measuring facial angle in degrees




SNB dg Mean S.D Min. Max. S.E.

Class I Group

(N = 140) 77.7 3.5 70.2 89.3 0.30

Class II Group

(N = 33) 76.3 2.4 72.0 80.5 0.42

Class III Group

(N = 32) 79.2 4.2 70.3 92.7 0.75





Facial Angle


Class I Group

(N = 140) 86.4 3.2 79.4 95.6 0.27

Class II Group

(N = 33) 84.5 3.2 77.9 93.0 0.56

Class III Group

(N = 32) 87.4 3.9 77.9 95.5 0.69





147


5.3.4 The Mandible … (continued)

Table 5.3.4.3 The mean and spread of measuring pog ┴ FH in mm




Table 5.3.4.4 The mean and spread of measuring pog/NB in mm recorded

for class I, class II, class III skeletal relationship of Saudi females. The t-

value of the mean difference of (class I - class II) and (class I - class III) is

shown with its level of significance

pog ┴ FH mm Mean S.D Min. Max. S.E.

Class I Group

(N = 140) -8.1 6.1 -22.9 12.5 0.51

Class II Group

(N = 33) -11.2 4.7 -18.8 -3.3 0.82

Class III Group

(N = 32) -5.2 6.9 -19.3 15.4 1.20





Pog/NB Mean S.D Min. Max. S.E.

Class I Group

(N = 140) 0.8 1.2 -2.3 4.8 0.10

Class II Group

(N = 33) 0.1 1.0 -2.1 2.8 0.17

Class III Group

(N = 32) 1.3 1.1 0.7 4.1 0.20





148


5.3.4 The Mandible … (continued)

Table 5.3.4.5 The mean and spread of measuring mandibular body length

in mm recorded for class I, class II, class III skeletal relationship of Saudi


I - class III) is shown with its level of significance

Table 5.3.4.6 The mean and spread of measuring mandibular length in mm




mandibular

body length

mm

Mean S.D Min. Max. S.E.

Class I Group

(N = 140) 60.3 4.1 47.6 70.6 0.35

Class II Group

(N = 33) 59.2 3.2 54.1 65.3 0.56

Class III Group

(N = 32) 61.5 3.6 53.7 68.0 0.63





mandibular

length mm Mean S.D Min. Max. S.E.

Class I Group

(N = 140) 94.4 5.1 80.8 109.6 0.43

Class II Group

(N = 33) 91.9 4.9 83.6 102.8 0.86

Class III Group

(N = 32) 95.1 5.1 83.0 106.2 0.91





149


5.3.4 The dento alveolar relationship

5.3.5.a Maxillary incisor position

Table 5.3.5.a.1 The mean and spread of measuring UIE/NA in mm




Table 5.3.5.a.2 The mean and spread of measuring UIE/A ┴ FH in mm




UIE/NA


Class I Group

(N = 140) 5.9 2.2 -3.0 11.9 0.1

Class II Group

(N = 33) 4.0 2.6 -1.8 10.2 0.4

Class III Group

(N = 32) 8.5 2.2 3.6 12.4 0.3





UIE/A ┴ FH


Class I Group

(N = 140) 4.3 2.3 -5.5 12.0 0.19

Class II Group

(N = 33) 3.2 2.4 -2.0 9.2 0.41

Class III Group

(N = 32) 5.6 2.4 0.08 11.3 0.43


Level of significance – *



150


5.3.4 The dento alveolar relationship … (continued)

5.3.5.a Maxillary incisor position … (continued)

Table 5.3.5.a.3 The mean and spread of measuring UIE/A pog in mm




Table 5.3.5.a.4 The mean and spread of measuring UIA-UIE/NA in




UIE/A Pog


Class I Group

(N = 140) 6.9 2.3 -3.2 13.1 0.19

Class II Group

(N = 33) 8.1 2.5 3.5 13.8 0.44

Class III Group

(N = 32) 6.2 2.2 0.9 10.4 0.4





UIA-UIE/NA


Class I Group

(N = 140) 25.6 5.8 2.6 40.6 0.49

Class II Group

(N = 33) 22.3 6.8 9.2 36.8 1.1

Class III Group

(N = 32) 32.0 5.0 20.6 43.6 0.89





151



5.3.5.a Mandibular incisor position

Table 5.3.5.b.1 The mean and spread of measuring LIE/NB in mm




Table 5.3.5.b.2 The mean and spread of measuring LIE/Apog in mm




LIE/NB


Class I Group

(N = 140) 6.6 2.0 -0.8 12.0 0.17

Class II Group

(N = 33) 8.4 2.2 4.2 14.3 0.38

Class III Group

(N = 32) 5.1 2.1 1.6 9.1 0.37





LIE/Apog mm Mean S.D Min. Max. S.E.

Class I Group

(N = 140) 3.6 2.2 - 5.8 10.5 0.19

Class II Group

(N = 33) 3.4 2.4 -0.6 9.2 0.42

Class III Group

(N = 32) 4.0 2.4 0.08 9.2 0.43





152



5.3.5.a Mandibular incisor position … (continued)

Table 5.3.5.b.3 The mean and spread of measuring LIE-LIA/NB in degrees




Table 5.3.5.b.4 The mean and spread of measuring LIA-LIE/MP2 in




LIE-LIA/NB


Class I Group

(N = 140) 30.4 5.5 10.0 43.5 0.47

Class II Group

(N = 33) 33.4 5.0 25.9 43.4 0.87

Class III Group

(N = 32) 26.0 5.2 17.4 39.1 0.93





LIA-LIE/MP2


Class I Group

(N = 140) 97.0 5.9 -10.1 20.5 0.5

Class II Group

(N = 33) 99.5 5.8 -0.4 21.2 1.0

Class III Group

(N = 32) 93.8 6.2 -9.0 18.2 1.1





153



5.3.5.c The maxillary-mandibular incisor relation … (continued)

Table 5.3.5.c.1 The mean and spread of measuring interincisal angle in




Interincisal

Angle dg Mean S.D Min. Max. S.E.

Class I Group

(N = 140) 120.6 9.1 97.7 163.5 0.77

Class II Group

(N = 33) 117.2 9.6 96.6 137.2 1.6

Class III Group

(N = 32) 121.9 7.8 102.7 135.0 1.3





154

5.4 Comparison of the skeleto-dental characteristics of Saudi females

class I skeletal relationship (control group) to established mean

value of North American whites, (Riolo et al., 1974) and British

caucasian, (Bhatia and Leighton, 1993). The results of the comparison was also divided into 5 sections:

5.4.1 Skeletal relationship.

The results of skeletal relationship were presented for the antero

posterior dimension in Tables 5.4.l.a.1 to 5.4.l.a.3 and for the vertical

relationship in Tables 5.4.l.b.1 to 5.4.l.b.12.

It can be seen that the differences between the mean value of Saudi

control group compared to the established caucasian values showed

different level of significance in the anteroposterior dimension. When the

vertical dimensions of the Saudi and the British samples were compared,

the level of significance was found to be less.

5.4.2 Cranial base. The results of cranial base were presented in Tables 5.4.2.1 to

5.4.2.3. The results obtained showed no significant difference between the

Saudi and the British samples, on the other hand, all other comparisons

were significant.

155

5.4.3 Maxilla

The results of the maxillary measurements were presented in Tables

5.4.3.1 to 5.4.3.3. These results showed that the only insignificant

difference found between the Saudi and North American sample was in

SNA angle. The other values were significant.

5.4.4. Mandible.

The results of the mandibular measurements were presented in

Tables 5.4.4.1. to 5.4.4.6. The results revealed that the only insignificant

difference observed between the Saudi and North American sample was

in SNB angle. The other values showed differences.

5.4.5 Dento-alveolar relationship.

The results of measurements of the dento-alveolar relationship were

presented in Tables 5.4.5.a.1 to 5.4.5.a.4 (maxillary incisor position),

Tables 5.4.5.b.1 to 5.4.5.b.4 (mandibular incisor position), and Table

5.4.5.c.1 (maxillary-mandibular incisor position). It was noticed that, both

maxillary and mandibular incisor position (angular and linear

measurements) showed some degree of bimaxillary proclination when the

Saudi sample was compared to the British and the North American

samples.

156

5.4 Comparison of skeleto dental characteristics of Saudi females class

I skeletal; relationship (control group) to established mean value of

North American Caucasian and British Caucasian.

5.4.1 The skeletal relationship

5.4.1.a. The antero posterior skeletal relationship

Table 5.4.1.a.1 The mean and spread of measuring ANB in degrees

recorded for class I of Saudi female, North American Caucasian and British

caucaisian. The t- value of the mean difference of (Saudi-NAC) and

(Saudi-BC) is shown with its level of significance

NAC = North Americans Caucasians Norms

BC = British Caucasian Norms

NR = Not recorded

P 0.05 (

*) significant

P P 0.001 (***) very highly significant

NS = not significant

ANB dg Mean S.D

Saudi Class 3.1 1.1

N.A.C 3.8 2.2

B.C 2.9 2.4

t-value1 (Saudi-NAC) = 7.7


t-value2 (Saudi-BC) = 2.2


157

5.4 Comparison of skeleto dental characteristics … (continued)


5.4.1.a. The antero posterior skeletal relationship … (continued)

Table 5.4.1.a.2 The mean and spread of measuring AB plane angle in

degrees recorded for class I of Saudi female, North American Caucasian

and British caucaisian. The t- value of the mean difference of (Saudi-NAC)

and (Saudi-BC) is shown with its level of significance

Table 5.4.1.a.3 The mean and spread of measuring angle of convexity in




AB Plane Angle

dg Mean S.D

Saudi Class - 4.8 1.8

N.A.C -5.9 3.2

B.C -5.4 3.4





Angle of Convexity

dg Mean S.D

Saudi Class 5.4 3.2

N.A.C 6.6 4.5

B.C 5.4 6.1



t-value2 (Saudi-BC) = 0


158



5.4.1.b The vertical relationship

Table 5.4.1.b.1 The mean and spread of measuring SN/MP in degrees




Table 5.4.1.b.2 The mean and spread of measuring SN/occ in degrees




SN/MP1 dg Mean S.D

Saudi Class 35.8 5.1

N.A.C 34.6 5.3

B.C NR NR



SN/Occ

dg Mean S.D


N.A.C 17.9 4.5

B.C 20.5 4.4





159



5.4.1.b The vertical relationship … (continued)

Table 5.4.1.b.3 The mean and spread of measuring FH/MP2 in degrees




Table 5.4.1.b.4 The mean and spread of measuring FH/occ in degrees




FH/MP2

dg Mean S.D


N.A.C 28.8 4.4

B.C 25.1 4.8





FH/occ

dg Mean S.D


N.A.C 10.8 3.7

B.C 9.8 4.0




Level of significance –***

160



5.4.1.b. The vertical relationship … (continued)





Table 5.4.1.b.6 The mean and spread of measuring the facial axis angle in




Y Axis Angle

dg Mean S.D


N.A.C 60.6 3.7

B.C 56.9 3.5





Facial axis angle

dg Mean S.D


N.A.C NR NR

B.C 89.3 4.4



161




Table 5.4.1.b.7 The mean and spread of measuring gonial angle in degrees




Gonial Angle

dg Mean S.D


N.A.C 126.9 4.6

B.C 131.1 4.2





162




Table 5.4.1.b.8 The mean and spread of measuring ANS-Me in mm




Table 5.4.1.b.9 The mean and spread of measuring N-Me in mm recorded

for class I of Saudi female, North American Caucasian and British



ANS-Me

mm Mean S.D


N.A.C 65.8 4.6

B.C 58.1 4.5





N-Me mm Mean S.D


N.A.C 116.2 6.4

B.C 104.1 5.0





163




Table 5.4.1.b.10 The mean and spread of measuring S-Go in mm recorded




Table 5.4.1.b.11 The mean and spread of measuring ramus height in mm




S-Go

mm Mean S.D


N.A.C 71.1 4.4

B.C 65.2 4.1





Ramus Height

mm Mean S.D


N.A.C 42.3 3.1

B.C 38.9 3.1



t-value2 (Saudi-BC) = 0


164




Table 5.4.1.b.12 The mean and spread of measuring ANS-Me/N-Me

percentage recorded for class I of Saudi female, North American Caucasian




percentage recorded for class I of Saudi female, North American Caucasian



ANS-Me/N-Me % Mean S.D


N.A.C NR NR

B.C 52.7 1.1



S-go/N-Me % Mean S.D


N.A.C NR NR

B.C 64.8 4.0



165


5.4.2 The cranial base

Table 5.4.2.1 The mean and spread of measuring S-N in mm recorded for

class I of Saudi female, North American Caucasian and British caucaisian.

The t- value of the mean difference of (Saudi-NAC) and (Saudi-BC) is


Table 5.4.2.2 The mean and spread of measuring S-Ar in mm recorded for

class I of Saudi female, North American Caucasian and British caucaisian.

The t- value of the mean difference of (Saudi-NAC) and (Saudi-BC) is


S – N mm Mean S.D


N.A.C 74.3 3.0

B.C 64.2 1.9





S-Ar mm Mean S.D


N.A.C 33.0 3.7

B.C 30.5 3.0





166


5.4.2 The cranial base … (continued)

Table 5.4.2.3 The mean and spread of measuring saddle angle in degrees




5.4.2 The Maxilla

Table 5.4.3.1 The mean and spread of measuring SNA in degrees recorded




Saddle Angle dg Mean S.D


N.A.C NR NR

B.C 124.7 4.4



SNA dg Mean S.D


N.A.C 81.1 3.8

B.C 79.9 3.4





167


5.4.2 The Maxilla … (continued)

Table 5.4.3.2 The mean and spread of measuring A/N ┴ FH in mm




Table 5.4.3.3 The mean and spread of measuring maxillary length in mm




A/N ┴ FH mm Mean S.D

Saudi Class -1.9 3.2

N.A.C NR NR

B.C 0.9 3.0



Maxillary length mm Mean S.D


N.A.C NR NR

B.C 78.2 3.0



168


5.4.4 The mandible

Table 5.4.4.1 The mean and spread of measuring SNB in degrees recorded




Table 5.4.4.2 The mean and spread of measuring facial angle in degrees




SNB dg Mean S.D


N.A.C 77.3 3.9

B.C 77.0 3.4





Facial Angle dg Mean S.D


N.A.C 84.6 2.7

B.C 88.7 3.2





169


5.4.4 The mandible … (continued)

Table 5.4.4.3 The mean and spread of measuring mandibular body length

in mm recorded for class I of Saudi female, North American Caucasian and

British caucaisian. The t- value of the mean difference of (Saudi-NAC) and


Table 5.4.4.4 The mean and spread of measuring mandibular length in mm




Mandibular body length

mm Mean S.D


N.A.C 70.6 3.9

B.C 63.3 3.5





Mandibular length mm Mean S.D


N.A.C 113.4 4.7

B.C 101.3 4.2





170


5.4.4 The mandible … (continued)

Table 5.4.4.5 The mean and spread of measuring Pog/N ┴ in mm recorded




Table 5.4.4.6 The mean and spread of measuring Pog/NB in mm recorded




Pog/N ┴ mm Mean S.D

Saudi Class -8.1 6.0

N.A.C NR NR

B.C -1.8 5.6



Pog/NB mm Mean S.D

Saudi Class 0.8 1.2

N.A.C 1.2 1.2

B.C 1.6 1.9





171


5.4.5 The dentoalveolar relationship

5.4.5.a Maxillary incisor position

Table 5.4.5.a.1 The mean and spread of measuring UIE/NA in mm




Table 5.4.5.a.2 The mean and spread of measuring UIE/A ┴ FH in mm




UIE/NA mm Mean S.D

Saudi Class 5.9 2.2

N.A.C 3.9 2.4

B.C 3.3 1.9





UIE/A ┴ FH mm Mean S.D

Saudi Class 4.3 2.3

N.A.C NR NR

B.C 0.7 3.0



172


5.4.5 The dentoalveolar relationship … (continued)

5.4.5.a Maxillary incisor position … (continued)

Table 5.4.5.a.3 The mean and spread of measuring UIE/A pog in mm




Table 5.4.5.a.4 The mean and spread of measuring UIA-UIE/NA in




UIE/A Pog mm Mean S.D

Saudi Class 6.9 2.3

N.A.C 6.5 2.7

B.C 4.5 2.0





UIA-UIE/NA dg Mean S.D


N.A.C 24.8 6.1

B.C 22.0 6.4





173



5.4.5.b Mandibular incisor position

Table 5.4.5.b.1 The mean and spread of measuring LIE/NB in mm




Table 5.4.5.b.2 The mean and spread of measuring LIE/A pog in mm




LIE/NB mm Mean S.D

Saudi Class 6.6 2.0

N.A.C 4.5 2.3

B.C 3.3 2.4





LIE/A Pog dg Mean S.D

Saudi Class 3.6 2.2

N.A.C 1.6 2.3

B.C 1.1 2.3





174



5.4.5.b Mandibular incisor position … (continued)

Table 5.4.5.b.3 The mean and spread of measuring LIE-LIA/NB in degrees




Table 5.4.5.b.4 The mean and spread of measuring LIA-LIE/MP2 in




LIE-LIA/NB dg Mean S.D


N.A.C 25.3 6.0

B.C 23.9 7.5





LIA-LIE/MP2 dg Mean S.D


N.A.C 93.4 5.8

B.C NR NR



175



5.4.5.b Mandibular incisor position … (continued)

Table 5.4.5.c.1 The mean and spread of measuring interincisal angle in




Interincisal Angle dg Mean S.D


N.A.C 126.9 9.1

B.C 131.7 10.5





176

6.0 Discussion

177

6.0 Discussion

The discussion of this study will have the division as the previous part

(5.0). It begins with a discussion of the material and method.

6.1 Material and method used:

This retrospective cephalometric study, was based on cephalometric

radiographs collected previously, so most of the variables and criteria used

in taking the radiographs were previously established. However, it was

decided to take a subset of the Saudi sample from the large pool of the

radiographs, and certain criteria were set in order to select the sample for

the study. The criteria applied were principally concerned with the quality

of the radiographs which received first priority in selection because poor

quality radiographs would give poor results. First molar should be in

occlusion, because this would ensure that the occlusion or vertical

relationship of all subjects is standardized. Further, there should no

previous orthodontic treatment, and, there should be no cleft or craniofacial

deformity, in order to ensure the normal position of the jaws and teeth for

investigation and evaluation. The age of the subjects were in the range

from 10-12 years which the most probable age for the peak of pubertal

growth spurt, as documented by (Burstone, 1958; Graber, 1972 and

AIAmoudi et al., 1996).

178

It was well recognized scientific procedure when planning research

which requires frequent measurement, to determine the error which may

affect the results. Many authors such as Young (1962); Guilford and

Fruchter (1984); and Barford (1990) had described two types of errors

which can occur: systematic and random. In this study, which involves

measurements, these errors cannot be ignored. The systematic errors were

controlled by using only one cephalostat, two operators were involved, and

the development and storage of cephalograms were standardized. Further,

the magnification factors were determined and taken into account when the

results of this project were interpreted. The magnification factor was found

to be 10.6%, a value in general agreement with that reported by Baumrind

and Frantz (1971); Midtgard et al. (1974); Houston et al. (1986); Sandler,

1988). The strictly established criteria for selecting the radiographs require

Such criteria helped in minimizing the landmark identification error, and in

unifying the procedure.

6.2 The method error and reliability

The method error of this study was' evaluated by using well

established statistical procedure described by Dahlberg (1940) known' as

double determination method error, and also by using the coefficient of

179

reliability as described by Guilford and Fruchter (1984). The first method

will determine the error of a single measurement in recording the angular,

linear and proportional parameters. The coefficient of reliability will

determine the correlation between the first set and the second set of

measurements. These statistical procedures were employed to determine

the intra-examiner and inter-examiner error. In designing this study, thirty

radiographs were retraced by the investigator and the supervisor at

different occasions. The method error was determined and found to range

for the intra-examiner variation from 0.417° to 1.468° for angular

measurements, from 0.404 mm to 0.711 mm for linear measurements, and

from 0.447% to 0.531 % for proportional measurements. The inter-

examiner method-error ranged from 0.698° to 2.912° for angular

measurements, from 0.662mm to 1.144mm for linear measurements and

from 0.768 % to 0.877 % for proportional measurements. Any reading

more than 1.2 should be considered as large error and the reading should

be underestimated (Dahlberg, 1940). From the Tables 5.1.1, 5.1.2 and

Table 5.1.3 the only readings found to have values more than 1.2 were

1.432° for SN/occ and 1.468° for FH/occ. These readings were related to

the occlusal plane, which is usually associated with large errors. ' This is in

agreement with the results obtained by Hatton and Grainger (1958); Miller

et al. (1966); Savara et al. (1966); Baumrind and Frantz (1971); Stabrun

and Danielsen (1982). The situation was slightly different when the inter-

examiner error was evaluated. The following readings were found to have

180

values more than 1.2°: SN/occ of 2.869°, FH/occ of 2.912°, LIA-LIE/MP2

of 1.432°, LIE- LIA/NB of 1.472°, interincisal angle 1.469°, Pog/N ┴ FH

of 1.484 mm. The greater error values were not surprising, because in any

research, the inter-examiner error was usually larger than intra-examiner

error as reported by Hixon (1960); Broadway et al. (1962), Bennett and

Smales (1969); Kvam and Krogstad (1972). Further, the support for

method error which comes from the coefficient of reliability showed a very

high correlation value except for the following reading of SN/occ of 0.546°

and FH/occ of 0.513° in inter-examiner error. However, Houston (1983)

mentioned that when considering the coefficient of reliability, any reading

below 0.9 should be treated with suspicion. Following this criterion, the

following parameters should be considered very carefully: for intra-

examiner, SN/occ = 0.895°, FH/occ = 0.894°; for inter-examiner, angular

measurements SNA = 0.899°, LIA-LIE/MP2 = 0.896°, UIA-UIE/NA =

0.893°, LIE-LIA/NB = 0.885°, interincisal = 0.896°; and for linear

measurements A/N ┴ FH of 0.892mm, Pog/N ┴ FH of 0.885mm, Go-me

of 0.892mm.

6.3 The skeletal classification of Saudi sample

The widely accepted use of the ANB angle as a method for skeletal

classification (Taylor and Hitchcock, 1966; Freeman, 1981) was adopted in

this study. An ANB mean value of 2.9° with a standard deviation of 2.4°,

accepted as a representation of white caucasian by Bhatia and Leighton

(1993), was taken as a normal for the ANB value. As it has been

181

mentioned before, the Arabian population belongs to the caucasian

(Masoud, 1981). Bhatia and Leighton (1993) was preferred to the other

main reference (Riolo et al., 1974) because it covered a larger sample size.

The frequency of skeletal discrepancy among the 205 Saudi females

was found in class I; 140 out of 205; for class II; 33, and for class III 32;

that is, by percentage 68.3%, 16.1 % and 15.6%, respectively. These

figures follow the generally observed data that class I would be the largest,

in a sample followed by class II and class III (Luffingham and Campbell,

1974; Farawana, 1987; and Jones, 1987).

In this sample, the cases with a class III skeletal relation was larger

than that in the western populations, which has a percentage less than 5 %

(Angle, 1907; Ainsworth, 1925; Seipel, 1946; Bjork, 1947; Krogman,1951;

Walther, 1960; Ast et al., 1965; Haynes, 1970; Magnusson, 1976;

Hannuksela, 1977; Gardiner, 1982). On the other hand, this incidence of a

high-class III skeletal relationship in Saudi females was in agreement with

previous studies carried out on Saudi samples. For example, when Jones

(1987) did study consisted of both sexes, he found class I to be 46.4 % of

his sample, class 11 27.5 % and class III 26.1 %. Similarly, when Toms

(1989) studied class III, he found the percentage to be 9.4%.

182

6.4 The skeleto-dental characteristics of class II and class III

among Saudi sample


6.4.1.a Antero posterior skeletal relationship

The mean value of ANB in class II was 7.0° and in class I was 3.1°

with a difference of + 3.9, ° indicating a class II arrangement skeletal base.

Class III showed a mean value of -0.5° with a difference of -3.6° indicating

class III skeletal arrangement. The same approach can be applied for A-B

plane angle and angle of convexity. These results obtained were in

agreement with most reported studies previously (Harris, 1965; Horowitz

et al., 1969; Dietrich, 1970; Ahlgren, 1970; Harris et al., 1972; Hitchcock,

1973; Jacobson et al., 1974; Guyer et al., 1986; and Sarhan and Hashim,

1994).

6.4.1.b Vertical skeletal relationship

The results showed no significant difference between the three

skeletal classes. These findings were in agreement with Sanborn (1955);

Harris et al. (1972); Hitchcock (1973); Williams and Andreson (1986).

However, when each variable was tested separately, SN/MP1 revealed less

value for class III, than class I with significant level of difference. The

same was true for SN/occ. Thus there is, a significant difference between

class I and class III, but no significant difference was observed between

class I and class II for both variables.

When the posterior vertical dimension was assessed linearly and

proportionally, it showed no difference between class I and the two other

classes except for the short ramus height in class II cases (Tables 5.3.1.b.10

183

to 5.3.1.b.13), which was 1.5° less than class I. This finding was consistent

with Smeets (1962). The significant difference of short ramus height may

have implications for the arrangement of skeletal bases in other dimensions

and this will be investigated further. It should be noted that the analysis of

Y-axis angle and facial axis angle (Table 5.3.1.b.5 and Table 5.3.1.b.6)

showed a significant difference between class II and class III when they

were compared to class I separately. The Y-axis angle and facial axis angle,

as mentioned by Down (1948) and Ricketts (1960), indicate the direction of

mandibular growth. This can be described generally in this study as being

a downward and backward rotation of the mandible for class II and an

upward and forward rotation for class Ill. This finding is in agreement with

Drelich (1948); Dietrich (1970); Hitchcock (1973); McNamara (1981);

Hashim and Sarhan (1993); Sarhan and Hashim (1994).

6.4.2. Cranial base

The cranial base were assessed by linear and angular measurements.

The anterior cranial base, representing the measurement from point N to

point S, showed no significant difference between class II and class III.

This finding is in agreement with other investigators (Guyer et al., 1986;

Hashim and Sarhan, 1993; Sarhan and Hashim, 1994). Generally it was

noticed that class II had slightly larger cranial base, whereas, class III had

slightly shorter base. In this study, the result of the measurement for the

posterior cranial base from point S to Ar showed no statistical differences

between the three classes. The cranial base angle also showed no

184

significant differences between the three classes, this finding in agreement

with Guyer et al. (1986); Hashim and Sarhan (1993); Sarhan and Hashim

(1994). However, it was noticed from the mean value (Table 5.3.2.3) in

class II was slightly larger than the mean value in class I. This finding was

similar to the findings reported by Jarvinen (1984) who found class II

usually have high angle, and in contrast to the findings of Harris (1965)

who found smaller angle in class II. Further, class III had a smaller mean

value than class I. This was in agreement with Bjork (1947); Sanborn

(1955); Horowitz et al. (1969); Rakosi (1970).

6.4.3 Maxilla

In this study, both maxillary position and length were assessed. The

position of the maxilla relative to cranial base was assessed by two

variables. The first variable was SNA. The Saudi sample showed a mean

value of 80.8° for class I, 83.3° for class II, and 78.6° for the class III

skeletal relationship. It can be observed that class II is 2.5° more than class

I. This may indicate that the maxilla is protruded for class II. On the other

hand, for the class III skeletal relationship the mean value was 2.2° less

than class I, which would also indicate retrusive maxilla. The above finding

was supported by the second variable: the measurement from point A to

A/N ┴ FH. This has the following mean values: -1.9 mm, 0.3 mm, and -3.9

mm, for class I, class II, class III respectively. When maxillary length was

considered, the values were 74.9 mm for class I, 76.6 mm for class II, and

72.4 mm for class III. This finding indicated that class II had longer

185

maxilla and class III had shorter maxilla than class I. The findings for class

II were in agreement with Drelich (1948); Blair (1954); Altemus (1955);

Rothstein (1971); Amoric (1985); Rosenblum (1995). On the other hand,

Elsasser and Wylie (1943); Riedel (1952); Hunter (1967), and Hitchcock

(1973) found slightly different results. Their main finding was that the

maxilla was normal. The other researchers as Renfroe (1948); Henry

(1957); Harris et at. (1972); McNamara (1981), found the maxilla to be

retrusive. The results of class III were similar to those of Bjork (1947);

Sanborn (1955); Jacobson et al. (1974); Williams and Anderson (1986);

Guyer et al. (1986), while Horowitz et al. (1969) found normal maxilla in

class III.

6.4.4 Mandible

Similar to maxilla, the mandibular position and size were determined,

in addition to that the chin prominence was measured. The position of the

mandible relative to the cranial base was assessed by several variables. The

SNB angle gave the readings of 77.7°, 76.3°, and 79.2° for class I, class II,

and class III, respectively. This indicated that the mandible had a retruded

position for class II and relatively protruded in class III. When facial angle

was considered, the values of 86.4° for class I, 84.5° for class II and, 87.4°

for class III were obtained indicating that the mandible was retruded for

class II and normal for class III. On the other hand, when the linear

measurement Pog/N ┴ FH was assessed, the finding showed that the

mandible was retrusive in class II and protrusive in class III.

186

The mandibular length was also considered. For the measurement of

body length, class I has a value of 60.3 mm; class II 59.2 mm, and class III,

61.5 mm. The total mandibular length including the ramus height had a

value of 94.4 mm, 91.9 mm, and 95.1 mm, for class I, class II and class III,

respectively. This finding showed that, for class II the body length of the

mandible was normal, whereas, the total length of the mandible was

slightly less than normal. This may be due to a short ramus. In class III,

however, the body length and total mandibular length were found to be

normal.

The above results may indicate that the mandible had a relatively

normal position and normal size in the saudi sample for class III, and a

retruded mandibular position and normal size in class II. To assess the

prominence of the chin, the linear measurement between the line NB and

point Pog was investigated for class II and class III in relation to class I.

The findings demonstrated a retruded chin point for class II, whereas, class

III showed no significant difference when compared to class I. The

findings for class II were in agreement with Elsasser and Wylie (1943);

Renfroe (1948); Drelich (1948); Nelson and Highly (1948); Gilmore

(1950); Craig (1951); Riedel (1952); Henry (1957); Hunter (1967); Harris

et al., (1972); Hitchcock (1973); McNamara (1981). The opposite was

found by Adams (1948); Blair (1954); Altemus (1955); Rothstein (1971),

who found a normal mandible. The finding of this study for class III agreed

with Dietrich (1970); Ellis and McNamara (1984); Williams and Anderson

(1986).

187

When considering the relative position of the maxilla and the

mandible and their sizes, it was concluded that class II has a protruded

maxilla, and retrusive mandible, whereas, class III has retrusive maxilla

and relatively normal mandibular position and size. These results suggest

accepting the research hypothesis "the skeletal discrepancies of class II and

class III skeletal relationship were attributed mainly to a positonal and/or a

dimensional cause".

6.4.5 Dento-alveolar relation

The dento-alveolar relationship was assessed for maxillary and

mandibular incisor position and relation using both angular and linear

measurement.

6.4.5.1 Maxillary incisor position

The linear measurement of the tip of upper incisor to a predetermined

reference line showed retrusion of the tip of the upper incisor in the class II

skeletal relationship (Tables 5.3.5.a.1 to 5.3.5.a.3) and protrusion in class

III cases. The differences between the mean values of class I to the other

classes showed a high level of significance except for the position of upper

incisor teeth in relation to A-Pog line in class III cases. This may be due to

the position of point Pog in class III being forward. In class II cases, the

position of upper incisor in relation to A-Pog line has greater value than

class I. This agreed with the finding of Hunter (1967); Rothstein (1971);

Harris et al. (1972); Hitchcock (1973); and McNamara (1981). The

188

literature reported some controversy regarding the position of the upper

incisor for class II and class III. The result of this study was similar to the

finding of Bjork (1947); Dietrich (1970); Rakosi (1970); Jacobson et al.

(1974); Moss (1976); Guyer et al. (1986); and Toms (1989), for class III

cases. Similar results of this study was reported by Jones (1987) for class II

But it was in disagreement with Henry (1957) who found that the

maxillary incisors were normal. The angular measurements of upper

incisor teeth measured between the long axis of upper incisor and NA line

(see Table 5.3.5.a.4) confirmed the retroclination of upper anterior teeth in

class II cases. The mean value in class II was 22.30 class I 25.6

0 and class

III 32.0.0 This indicated retroclination of upper incisor in class II and

proclination in class III. These findings agreed with the theory proposed by

Bjork (1947); Robinson et at. (1972); Waite and Worms (1974); Worms et

al. (1976); Thomas et al. (1977); Solow (1980), that teeth tend to

compensate for the underlying skeletal discrepancy by changing their

angulation. According to this theory, the upper anterior teeth are expected

to be retroclined in class II and proclined in class III. The finding of this

study is in full agreement with this theory.

6.4.5.2 Mandibular incisor position

Similar to the upper incisors, the lower incisors were measured by

linear and angular parameters. The linear position of the tip of lower

incisor teeth in relation to the NB line (Table 5.4.5. b.1. and Table

5.4.5.b.2) showed proclination of lower incisor teeth in class II and slight

189

retroclination in class III. The mean values were 6.6°, 8.4° and 5.1° for

class I, class II and class III respectively, with highly significant

differences between class I, and class II, and between class I and class Ill.

The position of the lower incisor in relation to A-Pog line showed very

slight variation between the three classes with slight retroclination in class

II and very slight proclination in class III. This may be due to the influence

of the lower lip and the tongue. The mean value of the angular

measurement of the position of the lower incisor teeth showed proclination

of lower incisor teeth in class II and retroclination in class III (Tables

5.3.5.b.3 and 5.3.5.b.4). These findings were in agreement with the

findings of Bjork (1947); Worms et al. (1976); Thomas et at: (1977);

Solow and Tallgren (1977); Solow (1980), Jones (1987) Toms (1989).

6.4.5.3 Inter incisal angle

The inter-incisal angle is the most commonly used measurement for

the relationship of upper incisor teeth to the lower incisor teeth. In this

study, the mean value of the inter-incisal angle in class I was 120.6°

9.1°, class II, 117.2° 9.6° and class III 121.9° +7.8°. The difference in

this angle was significant when class I was compared to class II, and not

significant when class III was compared to class I. This result could be

attributed to the compensatory mechanism caused by the underlying

skeletal discrepancy. Other influential factors e.g. lip position and

morphology, tongue position and size, etc. should not be ignored.

However, firm conclusion can not be stated. A soft tissue study may be of

190

great help in explaining this relationship.

6.5 Comparison of the skeleto-dental characteristics of

Saudi females to the established cephalometric

standards

The results of the present study could be of great value for the

orthodontist in the diagnosis and treatment plan when treating Saudi

patients. However, the results would be invaluable when compared with

well-known cephalometric studies. This could add more informations to

the literature and help for future studies.

In this study, the results obtained for the Saudi females with skeletal

class I were compared to the most widely known studies, namely Riolo et

al. (1974) and Bhatia and Leighton (1993). The results of comparison were

presented in Tables 5.4.1.a.1 to 5.4.5.c.1.


6.5.1.a Antero-posterior skeletal relationship

Although the ANB (2.9°+ 2.4°) reported by Bhatia and Leighton

(1993) was used in the skeletal classification of the Saudi sample. The

result of comparing the Saudi females to British Caucasian showed

significant differences. Similarly, significant difference between Saudis

and North American caucasian data were observed. The level of

significance was very high (P<0.001) for the North American (Table

5.4.1.a.1). Further, when the A-B plane angle was used to compare

between the Saudi and the other two groups, the level of significance was

191

very high (P < 0.001) between Saudi, British and North American. No

significant difference was observed in the angle of convexity between

Saudi females and the British Caucasians, whereas, it was significant (P <

0.001) when compared to North American Caucasians. These differences

between the three groups could be due to the variation in samples. This

finding will not suggest rejecting the stated hypothesis that "Saudi Arabian

population belong to Caucasian race, but that then they should have similar

skeleto-dental characteristics". When the skeletal relationship of the same

ethnic sub-group was compared by different investigators, a similar finding

to this study was reported (Miura, 1968; Chan, 1972); Richardson, 1980;

and Haralabakis et al., 1983).

6.5.1.b Vertical relationship

The angular measurements of the various vertical skeletal

relationships showed significant differences between class I skeletal

relationship of Saudi sample when compared to North American Caucasian

and British Caucasian except when the gonial angle in the Saudi sample

was compared to the North American (Tables 5.4.1.b.l to 5.4.1.b.7). There

was no significant difference between the Saudi female and British

Caucasian when comparing total anterior facial height, total posterior facial

height and ramus height. On the other hand, significant differences at 0.1 %

level was observed when the Saudi was compared to the North American

(Tables 5.4.1. b. 9 to 5.4.1b/11). The lower facial height measured from

ANS to Me (Table 5.4.1.b.8) showed a significant difference between

192

Saudi and both North American and British samples, which indicates that

the Saudi sample has relatively less excessive vertical anterior'

development. In general, the comparison of Saudi to North American

sample was highly significant. The comparison of vertical height

proportion also showed highly significant difference between the Saudi and

British Caucasian samples. This difference may be due to the variation in

the samples.

6.5.2 Cranial base

The linear measurements of the cranial base showed no significant

differences between the Saudi female and British caucasian for anterior

cranial base (Table 5.4.2.1). Posterior cranial base revealed significant

difference between the Saudi female and the North American and the

British samples. The saddle angle (measured from NS to Ar) showed

significant difference between the Saudi females and British samples

(Table 5.4.2.3). Such comparison was reported in different studies (Bjork,

1947) and the results were controversial. This could be due to variation in

the samples or landmark identification.

6.5.3 Maxilla

The relative position of maxilla (SNA) was significantly different

between the Saudi females and British Caucasian. No difference was

observed when Saudi females were compared to North American sample

(Table 5.4.3.1). The Saudi females showed a short maxilla when compared

193

to the British Caucasians (P < 0.001).

6.5.4 Mandible

Measurements of the mandibular position and size in both angular

and linear measurements showed significant differences between Saudi,

British and North Americans samples (P < 0.001). The SNB angle did not

show significant difference between Saudi and North American samples

(Table 5.4.4.1). However, a significant difference at 5% level was observed

when the Saudi females compared to the British Caucasian.

6.5.5 Dento-alveolar relationship

The dentoalveolar relationship was studied to see if there was any

difference in the position and relation of the incisor teeth between the saudi

female and British and North American caucasian (Tables 5.4.5.a.1 to

5.4.5.c.1). The results showed statistically significant differences in all

variables studied. However, no significant difference was observed when

the upper central incisor inclination in Saudi females was compared to the

British Caucasian (Tables 3.4.5.a.1 to 5.4.5.c.1). The results of the dento-

alveolar relationship in the Saudi females revealed that there was more

protrusion in the incisor teeth than the British and North American

Caucasian. This finding was in agreement with studies carried out in other

Saudi samples (Shalhoub et al., 1987; Sarhan and Nashashibi, 1988; Toms,

194

1989; and Nashashibi et al., 1990). When comparing the skeleto-dental

characteristics features of the Saudi females to the established means for

British and North American Caucasians, it was found that the Saudi female

was nearer to the British sample than the North American Caucasian.

195

7.0 CONCLUSIONS

196

7.0 Conclusions

1. The results of this study suggest accepting the hypotheses, that the

Saudis belong to the Caucasian and that the discrepancy in the

skeletal relationship was attributed to positional and/or dimensional

variations.

2. The Saudi sample showed a higher prevalence of class III than the

British and North American Caucasians.

3. Skeletal class II was found to be due to both protruded maxilla and

retruded mandible.

4. Skeletal class III was observed to be due to a retruded maxilla and

relatively normal mandible.

5. The Y-axis and facial axis angles indicate that the mandibular

rotation for class II was in a backward direction, whereas, for class III

in a forward direction.

6. In the vertical relationship, significant difference was observed in

most of the compared variables between the Saudi and British and

North American samples.

7. Dento-alveolar compensation was observed in class II (retruded

upper incisor and protruded lower incisor) and class III (protruded

upper incisor, and retruded lower incisor).

197

8. Bi-maxillary protrusion was observed when comparing the skeletal

class I of the Saudi females to the skeletal class I of the British and

North American Caucasians.

9. The skeleto-dental characteristic features of Saudi females were

nearer to the British sample than to the North American Caucasian.

198

7.1. Suggestions for Future Studies

Although this study has fulfilled its aims, there are several aspects,

which should be considered in future studies. These include:

1. A large randomly selected sample of both males and females should

be collected from the different provinces of the Kingdom, with more

variables to be studied, e.g. soft tissue.

2. More sophisticated computer with advance statistical programs

should be used.

199

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