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GROWTH MODULATION USING FUNCTIONAL

APPLIANCES - CEPHALOMETRIC PREDICTORS OF

SUCCESSFUL RESPONSE

Dr. Sharanya Ajit Kumar, Dr. K. Sadashiva Shetty, Dr. A.T. Prakash

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Authors

Dr. Sharanya Ajit KumarDr. K. Sadashiva Shetty Dr. A.T. Prakash

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Authors

Dr. Sharanya Ajit Kumar, B.D.S, M.D.S, Senior Lecturer, Dept of Orthodontics and Dentofacial Orthopedics, , Vydehi Institute of Dental Sciences & Research Centre, #82, E.P.I.P Area, Nallurahalli, Whitefield Bangalore - 560066, Karnataka, India

Email – drsharanyaortho@gmail.com Dr. K. Sadashiva Shetty, M.D.S, Professor and

Head, Dept of Orthodontics and Dentofacial Orthopedics, and Principal, Bapuji Dental College & Hospital, Davangere, Karnataka, India. Email- bapujidental@gmail.com

Dr. A.T. Prakash, M.D.S, MOrth RCSEd, Reader, Dept of Orthodontics and Dentofacial Orthopedics, Bapuji Dental College & Hospital, Davangere, Karnataka, India, Email- atportho@gmail.com

Corresponding author- Dr. Sharanya Ajit Kumar

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INTRODUCTION

Control and modification of growth of the skeletal structures of the craniofacial complex, Prominent but controversial area of

interest and activity within the field of orthodontics since its inception.

Growth modulation : functional appliances -topic of much debate.

key factors to its success - correct diagnosis, case selection, appliance design and patient co-operation.

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Selecting cases that will ensure a successful response to functional appliance therapy remains a problem because the treatment results are often variable and unpredictable.

A treatment outcome that has been particularly questioned is the enhancement of mandibular growth.

Differing responses due to the design of the appliances. different functional appliance designs act in dissimilar

ways and are not directly comparable Individual differences in sensory and neuromuscular

response

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Assuming that a patient is compliant, pre-treatment skeletal morphological

factors are responsible for a favourable or an unfavourable treatment outcome.

Categorizing cases according to the orthopedic response to treatment provides an opportunity for comparing characteristics and identifying differences between those that responded with a skeletal change and those that did not.

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OBJECTIVES

To determine whether there are any skeletal morphologic features evident on a pre-treatment lateral cephalogram that may be used to predict a successful improvement in the sagittal dental base relationship during functional appliance therapy in patients with a Class II skeletal pattern.

To compare the treatment changes between cases which responded favorably to growth modulation using functional appliances and those which did not.

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METHODOLOGY

SOURCE OF DATA

24 patients with class II skeletal pattern treated with functional appliance therapy were selected for the study, from the Department of Orthodontics and Dentofacial Orthopedics, Bapuji Dental College and Hospital, Davangere.

Two sets of lateral cephalograms- Pre-treatment and Post-functional cephalograms were used for the study.

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CRITERIA FOR SELECTION OF DATA

Class II skeletal bases

Growing patients treated with functional appliance to advance the mandible – Twin Block or Frankel Appliance.

All patients were compliant.

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METHOD OF COLLECTION OF DATA

Pre-treatment and post-functional lateral cephalograms were analyzed and the change in the ANB angle was used to determine the skeletal response to treatment with functional appliance.

Based on the change in the ANB angle the patients were divided into two groups of 12 patients each: Group 1- 12 patients who demonstrated a

change in ANB angle of 4° or more were identified as the Skeletal group.

Group 2- 12 patients who demonstrated a change in ANB angle of 1° or less were identified as the Non Skeletal group.

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2 parts of study

Comparisons were made between the mean pre-treatment (T1) parameters of Group I (Skeletal) and Group II (Non skeletal) to assess any pre-treatment parameters which were significantly different between the groups.

Changes due to functional appliance therapy from pre-treatment (T1) to post-functional (T2) stage was measured as T2-T1 in both Group I (Skeletal) and Group II (Non skeletal). The mean changes seen in Group I (Skeletal) and Group II (Non skeletal) were then compared to assess the difference between changes brought about by growth modulation using functional appliances between both groups.

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STATISTICAL ANALYSIS

Descriptive data that included mean and standard deviation values were calculated for the linear, angular and percentage parameters.

Results were expressed as mean and Standard deviation. Comparative statistical analysis of the data between both groups was done using One Way Analysis Of Variance (ANOVA) – F-TEST.

  A ‘P’ value of < 0.05 was set for statistical

significance.

 

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LANDMARKS USED

REFERENCE LINES PLANES

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LINEAR PARAMETERS

1. Sella-Nasion2. Sella-Articulare3. Upper anterior

facial height (UAFH)

4. Lower anterior facial height (LAFH)

5. Condylion-Gonion 6. Condylion-

Gnathion7. Gonion-Gnathion8. Overbite9. Overjet

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ANGULAR PARAMETERS

1. Nasion-Sella-Articulare2. S-Ar-Go3. SNA4. SNB5. ANB6. SN-MxP 7. SN-MnP 8. MxP-MnP (Basal Plane

angle)9. UI to MxP10.LI to MnP11.Mandibular arc

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PERCENTAGE PARAMETER

Jarabak Ratio:

Posterior facial height (S-Go) multiplied by 100 and divided by Anterior facial height (N-Me).

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RESULTS

Comparisons were made between the mean pre-treatment (T1) parameters of Group I (Skeletal) and Group II (Non skeletal) to assess any pre-treatment parameters which were significantly different between the groups which may help in predicting the response to growth modulation.

Table 1 presents comparative data for the pretreatment cephalometric measurements at the start of treatment (T1) for the two groups.

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Pre-treatment (T1) Cephalometric Variables

VariableGroup 1 Group 2

F value P value SignificanceMean SD Mean SD

S-N (mm) 69.30 3.20 68.60 3.40 0.25 0.65 NS

S-Ar (mm) 34.10 3.10 33.10 2.50 0.76 0.39 NS

UAFH (mm) 48.30 2.30 49.50 3.70 0.88 0.36 NS

LAFH (mm) 51.80 6.30 53.90 3.80 1.04 0.32 NS

Cd-Go (mm) 49.80 4.10 48.80 3.90 0.38 0.54 NS

Cd-Gn (mm) 101.00 3.50 101.40 8.50 0.03 0.88 NS

Go-Gn (mm) 67.40 2.50 68.20 6.20 0.15 0.7 NS

overbite (mm) 3.60 1.70 3.30 2.10 0.19 0.67 NS

overjet (mm) 10.10 1.30 8.30 3.10 3.22 0.09 NS

NSAr (deg) 126.00 4.00 125.30 4.40 0.15 0.7 NS

SArGo (deg) 142.20 7.00 146.60 4.90 3.21 0.09 NS

SNA (deg) 80.30 3.50 79.80 3.00 0.1 0.76 NS

SNB (deg) 73.70 2.90 73.70 3.30 0 1 NS

ANB (deg) 6.60 1.40 6.20 1.30 0.57 0.46 NS

SN-MxP (deg) 8.10 3.90 9.80 2.00 1.94 0.18 NS

SN-MnP (deg) 30.00 3.90 34.40 3.60 8.28 0.05 S

Basal plane angle (deg)

21.90 4.40 25.30 2.30 5.76 0.05 S

Mand arc (deg) 31.70 3.40 31.10 4.10 0.12 0.74 NS

UI-MxP (deg) 55.80 8.30 60.80 4.20 3.35 0.08 NS

LI-MnP (deg) 104.80 2.90 100.30 7.00 4.07 0.06 NS

Jarabak ratio (%) 67.20 3.70 63.90 3.00 5.75 0.05 S

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Pre-treatment angular parameters

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Pre-treatment percentage parameter

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Changes due to functional appliance therapy from pre-treatment (T1) to post-functional (T2) stage was measured as T2-T1 in both Group I (Skeletal) and Group II (Non skeletal).

The mean changes seen in Group I (Skeletal) and Group II (Non skeletal) were then compared in Table 2 to assess the difference between changes brought about by growth modulation using functional appliances between both groups.

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Changes in Cephalometric Variables from Pre-Rx to Post-functional

VariableGroup 1 Group 2

F value P value SignificanceMean SD Mean SD

S-N (mm) 1.7 1.7 1.3 1 0.53 0.47 NS

S-Ar (mm) 1.7 1.6 1 1.8 0.97 0.34 NS

UAFH (mm) 1.8 1.5 2 1.5 0.16 0.69 NS

LAFH (mm) 5.1 3.5 4.3 2 0.52 0.48 NS

Cd-Go (mm) 4.5 3.3 1.9 1.8 5.8 <0.05 S

Cd-Gn (mm) 6.4 4.8 4.8 2.6 1.01 0.33 NS

Go-Gn (mm) 3.2 2.4 2.8 2.1 0.13 0.72 NS

overbite (mm) -1.1 2.1 -0.7 2 0.25 0.62 NS

overjet (mm) -6.5 2.8 -3.7 2.5 6.64 <0.05 S

NSAr (deg) -0.9 1.9 -0.2 2 0.88 0.36 NS

SArGo (deg) 1.2 5.6 -1.1 2.4 1.64 0.21 NS

SNA (deg) -0.3 1.8 0.4 1 1.63 0.22 NS

SNB (deg) 3.8 1.9 1 0.9 23.2 <0.001 HS

ANB (deg) -4.2 0.4 -0.6 0.5 369.8 <0.001 HS

SN-MxP (deg) -0.6 2.7 -0.6 2.1 0 1 NS

SN-MdP (deg) -1.2 3.5 0.3 2.3 1.34 0.26 NS

Basal plane angle (deg) -0.6 2.1 0.2 3.3 0.45 0.51 NS

Mand arc (deg) 0.4 3.6 0 4.2 0.07 0.8 NS

UI-MxP (deg) 8.3 7.9 4.9 5.6 1.42 0.25 NS

LI-MnP (deg) 3.8 5.8 0.3 3.4 3.08 0.09 NS

Jarabak ratio (%) 2.6 2.2 0.3 1.5 8.94 <0.01 S

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Change in linear parameters

 

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Change in linear parameters

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Change in angular parameters

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Change in percentage parameter

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Discussion

Comparison of ramus height (Cd-Go) between the 2 groups at pre-treatment stage revealed no significant difference. Thus the cases all had a short ramus at the start of

treatment.

But as a result of treatment the Cd-Go in the skeletal group increased a mean of 4.5 mm but in the non skeletal the mean increase was only 1.9 mm. - statistically significant. - successful cases the ramus growth in the vertical direction contributes to correction.

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In the skeletal group the overjet decreased to a significant extent (6.5mm) compared to the non skeletal group (3.7mm). the decrease in overjet can be attributed partly to the

forward position of the mandible in the skeletal group.

The mean change in SNB in skeletal group was found to be 3.8 +/- 1.9 deg and for non skeletal group was found to be 1 +/- 0.9 deg. -statistically highly significant. For those who responded skeletally, there is a much greater forward movement of B point.

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The comparison of the SN-MnP values between the groups at the pre- treatment stage showed that the mean value of SN-MnP in the skeletal group was 30 deg and for the non skeletal group was 34.4 deg.

The difference was statistically significant. This was in agreement with studies by Pancherz

and Franchi L. and Baccetti. They believed that the prognosis of treating class II malocclusions is partly dependant on mandibular plane angle.

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The mean pre-treatment value of basal plane angle in the skeletal group was found to be 21.9 deg and for the non skeletal group was found to be 25.3 deg.

The difference was statistically significant. This also goes to prove that the skeletal group at the pre-treatment stage had more converging jaw bases which reflect a more horizontal growth direction.

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The mean value of Jarabak’s ratio in the skeletal group was found to be 67.2 % and for the non skeletal group was found to be 63.9 %. The difference was statistically significant showing that at the pre-treatment stage the skeletal group had an increased PFH to AFH ratio indicating a more horizontal growth pattern compared to the non skeletal group.

The mean value of the change in Jarabak’s ratio in the skeletal group was found to be 2.6 % and for the non skeletal group was found to be 0.3 %. The difference was statistically significant implying that in the skeletal group a significant increase in the posterior facial height was achieved compared to in the non-skeletal group.

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Conclusion

The pre-treatment parameters which related to a favourable response were low mandibular

plane angle, low basal plane

angle, high Jarabak’s ratio

 

Also in those cases which responded favorably the changes seen were increase in Cd-Go, decrease in overjet, increase in SNB, increase in Jarabak’s

ratio

Pre treatment parameters

Changes seen

The opposite was true in cases which did not respond favorably.

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Significance

The significance of these results will only have clinical use if patients with high growth potential can be identified at the start of treatment.

Further work on a greater number of patients would be required to attempt to relate mandibular variables to such successful outcomes, eventually allowing the production of an index for mandibular features for various age groups.

This would give the most accurate prediction perhaps of whether or not growth modification with functional appliances would be possible in any individual case.

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SCOPE FOR FUTURE STUDY

A prospective study could be planned with sample size categorized uniformly considering the gender.

Increasing the sample size could facilitate more substantial results.

A three dimensional representation like Computed Tomography (CT) scan could give better results and less errors.

An index could be prepared to be used for case selection for growth modulation.

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