JIndianSocPedodPrevDent24290-1355342_034553

ISSN 0970 - 4388

Loss of space and changes in the dental arch after premature loss of the lower primary molar: A longitudinal study PADMA KUMARI B.a, RETNAKUMARI N.b

Abstract

The purpose of the study was to evaluate the space changes, dental arch width, arch length and arch perimeter, after the unilateral extraction of lower first primary molar in the mixed dentition period. A longitudinal study was conducted among forty children in the age group of 6-9 years, who reported for extraction of lower first primary molar in the department of Pedodontics, Govt. Dental College, Trivandrum. Study models were made from alginate impression taken before extraction and after extraction at the periodical intervals of two months, four months, six months and eight months. The mesiodistal width of lower first primary molar of the non-extracted side was taken as the control. The results of the study showed statistically significant space loss in the extraction side (P value <0.01) and no significant space loss in the control side (P value > 0.05). The rate of loss was greatest in the first four months. The arch width, arch length and arch perimeter had no significant change from initial to eight months follow up. The present study challenges the use of a space maintenance under the circumstances of premature loss of mandibular primary molar for preventing space loss.

Key words: Arch length, arch perimeter, arch width, space loss

Introduction

Pedodontists have traditionally accepted active supervision

of the developing dentition as major responsibility. Man

agement of space problems associated with the transitional

stages from primary to permanent dentition is a routine

component of pedodontic practice. The change from pri

mary dentition to the permanent dentition is a complex phe

nomenon, which is composed of a variety of physiological

adaptations of occlusion during this period. The exfoliation

of the primary teeth, the permanent teeth eruption and the

occlusion through independent, occur in a harmonious se

quence.[1,2] There are many morphogenetic and environmen

tal influences, which manage the occlusal development and

a disorder or deviation in any of these elements may influ

ence the occlusion. Among these elements, there is the im

portance of the primary teeth because when they are physi

ologically exfoliated, there is a favourable alveolar growth

and space for a better accommodation of the successor per

manent teeth.[3] The permanent teeth dislocation occurs in

the eruptive, pre functional and functional periods of the

eruption, that are within the primary arch and in the mixed

dentition stage.[4-7]

Richardson[8] observed that the most severe space problems

happen when the primary teeth, in particular the first pri

mary molars are exfoliated before the eruption of the per

manent molar. The premature loss of the primary molars

that results in mesial positioning of the first permanent molar

is of a great concern during the mixed dentition. Love and

Adams[9] found a greater percentage of space loss by mesial

aSenior Lecturer, Dept. of Pedodontics, bProf. and Head, Dept. of Pedodontics, Govt. Dental College, Trivandrum, India

migration of the posterior teeth than distal migration of

the anterior teeth, especially in the mandible. In majority of

children, the occlusion and space would be influenced by

premature extraction of primary molars and canines.

Growth and development and drifting patterns of teeth are

closely interdependent. In the field of pediatric dentistry

much emphasis should be put on these factors in order to

secure the optimal benefit of systematic dental care for the

child. It is well known that after early loss of deciduous

molars dental arch crowding arises in some cases, while in

other cases it does not. It has been suggested that large

jaws with normal spacing or over spacing are not influenced

by the premature loss of the deciduous teeth. A tendency

towards small jaws and space deficiency in the deciduous

arch, on the other hand, will probably cause closure of the

extraction gap resulting in crowding in the permanent den

tition.[10] Premature loss of a primary tooth is of concern not

only because of the loss of function, but also because of the

increased possibility that the other teeth may drift. It would

be useful in determining the treatment, if the dentist could

predict the sequel of premature loss of primary teeth.

As the premature loss of primary teeth is still a very com

mon situation within the population, this study was under

taken using longitudinal cast data to investigate the changes

after unilateral premature extraction of the mandibular first

primary molar in the mixed dentition stage.

Aim and Objectives

1. To evaluate the space changes in the extracted site.

2. To determine the changes in dental arch width.

3. To observe changes in the dental arch width.

J Indian Soc Pedod Prev Dent - June 2006 90

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Loss of space and changes in the dental arch

4. To evaluate the changes in the dental arch perimeter.

Materials and Methods

Forty children for the study. The patients were in the age

group of 6-9 years, who had reported for extraction of lower

first primary molar in the Department of Pedodontics, Govt.

Dental college, Thiruvananthapuram for an evaluation of

thirteen months. The selected patients were made as ho

mogenous as possible. In the final stage of the study, the

number of patients decreased to 30, as ten children did not

come for further follow up and they were excluded from the

study.

All the cases complied with the following criteria

1. The first permanent molars have erupted.

2. Patients indicated for unilateral extraction of mandibu

lar first primary molar due to extensive decay and hav

ing an intact anterior tooth.

3. The anteroposterior and lateral arch relationships were

acceptable.

4. Premature loss of the primary molar was defined as hav

ing an unerupted permanent predecessor for at least

two years after extraction of the deciduous first molar.

5. Parents and guardians who were willing to overweigh

the effects of not maintaining the extraction space.

Recordings

At the start of the study, the children were subjected to a

clinical examination and the medical and dental history of

the child was taken. Mandibular study models were prepared

from alginate impressions before extraction and immedi

ately after the impression procedure, the decayed first mo

lar was extracted. No space maintaining appliance was ad

vocated. Longitudinally, the procedure was repeated at each

follow up after two, four, six and eight months after extrac

tion. Thus each patient was subjected to evaluation at five

stages. The opposite non-extraction side was taken as the

control. Two dental arch models of each patient prior to

extraction and four models after the extraction of lower first

primary molar were used for the study.

Measurements on the casts

Four measurements concerning dental arch development

were performed on the extraction space, arch width, arch

length and arch perimeter using a measuring gauge.

Extraction space

The referent space was determined by measuring the dis

tance between the mesial midpoint of the second decidu

ous molar and the distal midpoint of the primary canine

[Figures 1 and 2].

1

2

Figures 1 and 2: Representative scheme of the dental arch with the referent extraction space

Figure 3: Representative scheme of the dental arch width measurement

Arch width

The arch width was measured between the central fossae

on the occlusal surface of two second primary molars [Fig

ure 3].

Arch length

The arch length was determined by the orthogonal distance

of the median point between the central incisors until the

tangent line to the distal face of the second primary molars

or mesial surface of the first permanent molars [Figure 4].

Arch perimeter

The arch perimeter was the measurement of the arc from

91 J Indian Soc Pedod Prev Dent - June 2006




Figure 4: Representative scheme of the dental arch length measurement

Figure 5: Representative scheme of the dental arch perimeter measurement

(a)

(b)

(c)

(d)

(e)

Figure 6: (a) Lower cast pre extraction, (b) Study model second month, (c) Study model - fourth month, (d) Study model - sixth month, (e) Study model - eighth month.

the mesial midpoint of the first permanent molar, through

the cusp tip of the first permanent molars. It was measured

by the brass wire method. Measurements were repeated

three times using different caliper from which an average

value of the measurement in millimeter was recorded and

analysed [Figure 5].

Statistical analysis

The analysis was done with Statistical Package for Social

Science Soft ware (SPSS) programme. Paired ‘t’ test was used

for the comparison of measurement of all parameters.

Results

The present study, was undertaken to evaluate the loss of

space and change in the dental arch after premature loss of

lower first primary molar among thirty children in the age

group of 6-9 years brought the results. The measurement of

the mesiodistal width of lower first primary molar on both

control and extraction side, before extraction and following

2, 4, 6 and 8 months after extraction are shown in table. It

was observed that there was a space loss in the extraction

side and no space in the control side. It was also noted that

space loss was maximum during the first four months and

consequently space loss was minimum during the period of

six to eight months. The result showed statistically signifi

cant space loss in the extraction side (P < 0.01) compared to

the control side, which is not statistically significant (P >0.05).

Comparison of the space changes of the lower first primary

molar between the initial and follow up examinations dur

ing 2 months, 4 months, 6 months and 8 months in both

control and extraction side are shown in Table 2 and Figure

6a-6e. The first primary molar space of the extraction side

during the follow up examinations after 2 months (7.72

±0.56), 4 months (7.03 ± 0.56), 6 months (6.62 ± 0.56)

and 8months (6.64 ± 0.44), were significantly lesser than

the control side. There are statistically significant difference

between the initial and the follow up examination in the

extraction side. No significant difference is noted between

the control side and the extraction side in the initial first

primary molar space.

Quantity of space loss in millimeter after the premature loss

of lower first primary molar is shown in Table 3. Space re

duction in the analyzed dental arch were measured to be

1.31 mm, 1.69 mm, 1.41 mm and 1.22 mm during the moni

toring in 2 months, 4 months, 6 months and 8 months re

spectively. Shows the mean changes of space reduction in

control side and extraction side during the period from ini

tial to eight months.

Measurements of arch width were analysed and the results

showed no significant change in the arch width between

the initial and the follow up examinations at 2, 4, 6 and 8

months intervals.

The measurements of arch length from initial and follow up





Table 1: Space changes in (mm) from initial to follow up examination - control side and extraction side

Case Control side Extraction side

Initial 2nd 4th 6th 8th Initial 2nd 4th 6th 8th

month month month month month month month month 1 9 9 9 9 9 9 7 6.5 6-5 6

2 8 8 8 8 8 8.5 7.2 6.5 6 6

3 8 8 8 8 8 8 8 7.5 7 6

4 7 7 7 7 7 8 8 7.5 7.5 7

5 8 8 8 8 8 8.5 8 7.5 7.5 7

6 9 9 9 9 9 8.5 8 7 7 6.5

7 8.5 8.5 8 8 8 7 6 6 6 6

8 8 8 8 8 8 8.5 8 8 7.5 7

9 8.5 8.5 8.5 8.5 8.5 9 8 7 6 6

10 8 8 8 8 8 9 8.5 8 7 6.5

11 8.5 8.5 8.5 8.5 8.5 8 8 7.5 6 6

12 8 8 8 8 8 8 7 6.5 6 6

13 9 9 9 9 9 9 8 7 6 6

14 9 9 9 9 9 8.5 8 7.5 7 7

15 9 9 9 9 9 8 8 7.5 7 7

16 8 8 8 8 8 8 7 7 6.5 6

17 8.5 8.5 8.5 8.5 8.5 7.5 7 7 6.6 6

18 8 8 8 8 8 7 6.5 6 6 6

19 7 7 7 7 7 7 7 6.5 6 6

20 9 9 9 9 9 8 7.5 7 7

21 9 9 9 9 9 8 8 7 6 6

22 9 9 9 9 9 9 8 7.5 7 6.5

23 8.5 8.5 8.5 8 8 8 8 7.5 7 7

24 8.5 8.5 8.5 8.5 8.5 8.5 8 7.5 7 7

25 8 8 8 8 8 8.5 8.5 8 7.5 7

26 7.5 7 7 7 7 8.5 8 8 7 7

27 9 9 9 9 9 8.5 8 7 7 6.5

28 8.5 8 8 8 8 8 7 6.5 6 6

29 8 8 8 8 8 8 7 6.5 6 6

30 9 9 9 9 9 9 8.5 8 7 6

Mean 8.31 8.32 8.33 8.28 8.23 7.72 7.03 6.62 6.4

SD 0.62 0.62 0.58 0.55 0.56 0.71 0.56 0.44 P value 0.21 0.32 0.22 0.57 0.001 0.001 0.001 0.001

Table 2: Comparisons of the space changes of lower first primary molar in different intervals - control side and extraction side

Period Control side P value Extraction side P value Initial 8.31 ± 0.52 0.05** 8.23 ± 0.52 0.021 2 months 8.33 ± 0.62 0.21** 7.77 ± 0.56 0.001 4 months 8.32 ± 0.62 0.32** 7.03 ± 0.56 0.001 6 months 8.33 ± 0.58 0.22** 6.62 ± 0.56 0.001 8 months 8.28 ± 0.55 0.57** 6.4 ± 0.44 0.001

examinations reveal no statistically significant change.

No statistically significant changes observed in the arch pe

rimeter in the initial examination to follow up examinations.

Discussion

Research dealing with space changes in the dental arch is

difficult to perform accurately because of the multifactorial

variance influencing the results. Most of the reports of re-

Table 3: Quantity of space loss from Initial to eight months - extraction side

Period between the Mean Percentage measurements 2 months 1.31 mm 39 4 months 1.69 mm 50 6 months 1.41 mm 42 8 months -1.22 mm 36

search studies were based on cross sectional data, limited

sample size and crude methodology that had led to miscon

ceptions of space changes of the dental arch in maxillary or





Table 4: Changes in arch width (mm) from the initial to follow up examinations

Case no. Initial 2 months 4 months 6 months 8 months 1 38 38 39 39.5 39.5 2 34 34 35.5 35.5 36 3 33 33 32.5 32.5 32 4 36 36 35 35 34 5 34 34 35 35 34 6 36 36 37 38 38.5 7 33 33 32 32 32 8 34 34 33 32 32 9 32 33 33 34 35 10 34 33 32 32 32 11 34 33 33 32 32 12 34 43 35.5 33 33 13 33 35 36 36 36 14 36 37 38 38 39 15 38 38 39 39 39 16 35 34 34 33 33 17 35 35 34 34 33 18 33 33 33 32 32 19 34 33 33 32 32 20 36 36 35 35 35 21 33 33 32 31 31 22 38 37 37 36 35 23 33 33 33 33 32 24 34 35 35 36 36 25 34 34 33 32 31 26 36 36 35 35 34 27 33 33 33 32 32 28 35 34 34 34 34 29 38 37 37 37 36 30 36 36 35 35 33 Mean 34.73 . 34.67 34.35 34.35 34.1 SD 1.72 1.64 2.02 2.33 2.49

P Value 0.88 0.71 0.47 0.26

Table 5: Changes in arch length (mm) from initial to follow up examinations

Case no. Initial 2 months 4 months 6 months 8 months 1 22 21 20 19 19 2 20 19 22 19 19.5 3 21 20 20 19 20 4 18 18 18 19 20 5 18 18 18 17 17 6 18 19 20 22 22 7 19 19 18 17 17 8 19.5 19.5 19 19 19 9 21 21 20 19 19 10 17.5 18 19 20 20 11 20.5 19 19 18 18 12 20 19.5 19 18 18 13 18 19 19.5 19 19 14 22 20 19 19 19 15 19 20 20 21 21 16 18 18 17.5 17 17 17 19 19 20 21 21 18 18 17.5 17 17 17 19 17.5 17 17 17 17 20 19 20 20 21 22 21 21 20 20 20 21 22 16 16 17 17 18 23 19 20 19 19 19 24 19 20 21 21 21 25 18 17 17 16 16 26 16 16.5 16.5 16.5 16.5 27 17.5 17 17 16.5 16.5 28 19 19 18 18 18 29 22 21 21 20 20 30 20 21 20 19 19 Mean 19.08 18.97 18.92 18.47 18.9 SD 1.62 1.4 1.45 1.56 1.68

P Value 0.77 0.68 0.31 0.67





mandibular arch. The present study tried to minimize the

errors conducting a longitudinal study by using strict ho

mogenous samples and focusing on unilateral extraction of

the mandibular first primary molar.

The present study was carried out to find out the space loss

due to the unilateral premature extraction of the lower first

primary molar. There is statistically significant space loss in

the extraction side (P value<0.01) and no significant space

loss in the control side (P value>0.05). The space changes

in the extraction side measured by the first primary molar

space after eight months (6.4 ± 0.44 mm) have shown sig

nificant space loss compared to the initial first primary mo

lar space (8.23 ± 0.52 mm) and the control side (8.31 ±

0.52 mm).

The result of the present study confirm with the conclusion

of the studies of Helm, Owen and Yng-Tzer J, Lin and Li-

Ching Chang.[11,12,14] They reported that space loss was more

common in the mandibular arch after the premature loss of

first primary molar. The results of the present study partly

support the conclusions that space in the mandible is lost

by both mesial migration of posterior teeth and distal move

ment of anterior teeth as reported by Osmar Aparecide

Cuoghi et al.[13]

The mean changes of space loss in the present study are

1.31 mm after 2 months, 1.69 mm after 4 months, 1.41 mm

after 6 months and 1.22 mm after 8 months. It is noted that

space loss is maximum during the first four months and

minimum is last four months. Concerning the rate of space

change, the greatest space loss occurred in the first four

months. The study reveals significant space loss during the

average eight months of experimental period.

It appears in the present study that the space loss in the

mandible is mostly due to distal movement of primary cus

pid during the following eight months. The possible expla

nation is that the erupting anterior incisors pushed the pri

mary cuspid towards the distal more than the erupting first

permanent molar did on the second primary molar towards

the mesial. The findings of the present study support the

findings to Johnsen[15] that the space changes occurred mainly

by the distal migration of primary cuspid in the intial stage.

The present study also investigated the changes in the arch

width, arch length and arch perimeter. No significant change

in the arch width, arch length and arch perimeter from ini

tial and the follow up examinations at 2 months, 4 months,

6 months and 8 months was observed. Lundstrom[16] em

phasized the importance of inheritance of dental arch, the

Table 6: Changes of arch perimeter (mm) from initial to follow up examination

Case no. Initial 2 months 4 months 6 months 8 months 1 85 83 82 82 82 2 72 74 74 75 75 3 84 83 82 82 83 4 75 75 74 75 75 5 76 76 74 74 75 6 76 76 77 77 78 7 78 77 75 75 75 8 75 75 77 77 77 9 74 75 74 73 72 10 72 72 73 73 72 11 79 78 78 77 77 12 72 72 70 69 70 13 70 72 73 74 74 14 75 76 77 78 78 15 80 80 79 78 78 16 71 70 68 68 68 17 73 72 72 71 70 18 71 70 69 68 68 19 75 75 76 76 76 20 73 73 72 72 72 21 74 73 72 72 72 22 73 72 71 70 70 23 71 72 73 75 76 24 74 73 73 72 72 25 75 76 76 77 77 26 75 75 74 77 78 27 74 76 77 77 78 28 72 74 74 75 75 29 71 70 69 69 68 30 74 75 77 76 78 Mean 74.63 74.67 74.4 74.5 74.5 SD 3.58 3.27 3.4 3.62 3.89 P value 0.97 0.8 0.89 0.94





exfoliation period, occlusal developmental stages and influ

ences in the dental arch perimeter.

Briefly, the space loss is mainly, by movement of the pri

mary cuspids distally and by a lesser degree by movement

of the first permanent molar and second primary molar

mesially, depending on the period of the referred tooth ab

sence.

The following conclusions are drawn from the present study

1. The premature loss of the lower first primary molar in

the mixed dentition resulted in statistically significant

space loss in the extraction side than in the control side.

2. The early space change of the mandibular dental arch

after premature loss of the mandibular primary first

molar is mostly by distal movement of the primary cus

pid towards the extraction space.

3. There is significant space change during the average

eight months of experimental period. The greatest space

loss is observed in the first four months after the pre

mature extraction.

4. There is no significant space change in arch width, arch

length and arch perimeter in the mandibular arch after

premature loss of the primary first molar during the ex

perimental period of eight months after extraction.

The present study challenges the use of a space mainte

nance under the circumstances of premature loss of man

dibular primary molar for preventing space loss.

Further studies are needed to be done, regarding not only

on space problems of primary first molars, but also involv

ing the second primary molars in either the maxillary or

mandibular arch.

References

1. Foster TD, Hamilton MC. Occlusion in primary dentitions. Br Dent

J 1960;126:76-9. 2. Moyers RE. Ortodontia. 4th ed. Cuanabara Koogan: Rio de

Janeiro; 1991. p. 107-8. 3. Baume U. Physiological tooth migration and its significance for

the development of occlusion. The biogenetic course of the deciduous dentition. J Dent Res 1950;29:123-32.

4. Johnsen DC. Space observation following loss of the mandibular first primary molars in mixed dentition. J Dent Child 1980;47:247.

5. Singh IJ. Space maintenance a review. J All India DA 1960;32:191-7.

6. Colisti UP, Cohen MM, Fales MH. Correlation between malocclusion oral habits and socioeconomic level of preschool children. J Dent Res 1960;39:450-4.

7. Keonfeld SM. Effects of premature loss of primary teeth and sequence of eruption of permanent teeth on malocclusion. J Dent Child 1953;20:2-13.

8. Richardson. The relationship between the relative amount of space present in the deciduous dental arch and the rate and degree of space closure to the extraction of a deciduous molar. Dent Pract Dent Rec 1965;16:111-8.

9. Love WD, Adams RL. Tooth movement into edentulous areas. J Prosthet Dent 1971;25:271-8.

10. Ronnerman A, Thilander B. Early loss of primary molars relationship to space conditions, dental development, facial morphology and the need for orthodontic treatment. Thesis: Gotherburg; 1977.

11. Helm S. Prevalence of malocclusion in relation to the development of the dentition. Acta Odont Scand 1970;28:1.

12. Owen DG. The incidence and nature of space closure following the premature extraction of deciduous teeth. A literature survey. J Orthod 1971;59:37-49.

13. Cuoghi OA, Bertoz FA, de Mendonca MR, Santos EC. Loss of space and dental arch length after the loss of the lower first primary molar: A longitudinal study. J Clin Pediatric Dent 1998;22:117-20.

14. Lin YT, Chang LC. Spaces after premature loss of the mandibular primary first molar: A longitudinal study. J Clin Pediat Dent 1998;22:311-6.

15. Johnsen DC. Space observation following loss of the mandibular first primary molars in mixed dentition. J Dent Child 1980;47:247.

16. Lundstrom A. The significance of early loss of deciduous teeth in the etiology of malocclusion. Am J Orthod 1955;41:819-26.

Reprint requests to: B. Padma Kumari, Dept. of Pedodontics Govt. Dental College, Trivandrum, India




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