Assessment of Dentoalveolar Compensation in Subjects with Vertical Skeletal Dysplasia: A Retrospective Cephalometric Study

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1 /jp-journals ORIGINAL ARTICLE JIOS Assessment of Dentoalveolar Compensation in Subjects with Vertical Skeletal Dysplasia: A Retrospective Cephalometric Study 1 Bhumi Narendra Modi, 2 AT Prakash, 3 Sadashiva Shetty, 4 ET Roy ABSTRACT Objective: This study was aimed at understanding the differences in dentoskeletal parameters in short face and long face individuals and to evaluate the factors governing overbite. Materials and methods: Pretreatment lateral cephalograms of 80 individuals were traced and analyzed. The sample was divided into four groups: short face male, short face female, long face male and long face female. The descriptive data for all the groups were obtained. Student s t-test (unpaired) was used to compare the dentoskeletal parameters of the groups and correlation analysis was used to study the factors governing overbite. Results: In this study, it was found that there were highly significant differences in the dentoskeletal parameters among the short face and long face groups. It was also revealed that not all short faces had deep bite and, similarly, not all long faces had open bite. Conclusion: Overbite was governed by a multitude of factors. In the long face group, the major factors governing overbite were lower anterior facial height and the height of anterior mandibular alveolar process. On the contrary, in the short face group, ANB angle and overjet were the governing factors. This study further highlights the interaction between the vertical and sagittal component of malocclusion. Keywords: Cephalometrics, Short face, Long face and overbite. How to cite this article: Modi BN, Prakash AT, Shetty S, Roy ET. Assessment of Dentoalveolar Compensation in Subjects with Vertical Skeletal Dysplasia: A Retrospective Cephalometric Study. J Ind Orthod Soc 2013;47(4): INTRODUCTION Vertical dimension of the face has been the most difficult to modify clinically with a multitude of orthodontic, orthopedic and surgical interventions. Problems in the vertical dimension include open bite and deep bite. 1 During growth, the vertical and sagittal relationship of the jaws is not always perfect. In cases where imperfections exist, the relationship between the jaws is secured through the eruption and positioning of the teeth along their own basal arches. This is referred to as dentoalveolar compensatory mechanism. 2 Subjects with anterior deep bite or open bite often deviate in the underlying skeletal pattern. In such patients, a surgical approach must be considered that requires presurgical 1 Lecturer, 2 Reader, 3 Principal and Head, 4 Professor 1 Department of Orthodontics, Goa Dental College and Hospital Bambolim, Goa, India 2-4 Department of Orthodontics and Dentofacial Orthopedics, Bapuji Dental College and Hospital, Davangere, Karnataka, India Corresponding Author: Bhumi Narendra Modi, Lecturer, Department of Orthodontics, Goa Dental College and Hospital, Bambolim, Goa, India modibhumi.5@gmail.com Received on: 29/11/11 Accepted after Revision: 31/6/12 decompensation. Alternatively, a nonsurgical treatment option would include further dentoalveolar compensation. The determination of the suitable option must be based on the feasibility of dentoalveolar compensation. 3 The role of compensation in the development of overbite has been demonstrated in previous studies. This can involve height, depth and volume of symphysis and anterior part of maxilla. 3 These studies, however, do not show the extent and mechanism of compensation in patients with extremes of long face and short face. There has also been conflicting literature on the factors which govern the overbite in such patients. Therefore, there is a need to study the differences in the dentoskeletal parameters in these patients and to evaluate the influence of various parameters on overbite in such groups and thus estimate the amount of compensation. This would provide us with valuable additional information for planning treatment. AIMS AND OBJECTIVES The purposes of the present study were as follows: 1. To evaluate the differences in the dentoalveolar and skeletal parameters in the short face and long face groups. 2. To study the factors governing overbite in long face and short face individuals and to elucidate whether dentoalveolar compensation can still render a normal incisor overbite. The Journal of Indian Orthodontic Society, October-December 2013;47(4):

2 Bhumi Narendra Modi et al MATERIALS AND METHODS 1. Source of data: Lateral cephalograms of 80 orthodontically untreated individuals (both male and female) selected from pre-existing files from the Department of Orthodontics and Dentofacial Orthopedics, Bapuji Dental College and Hospital, Davangere. 2. Materials used in the study: Standardized lateral cephalograms of orthodontically untreated patients 0.003" thick acetate tracing paper 0.3 mm lead pencil Geometry box (scale, protractor, setsquares, eraser, sharpener) Scotch tapes Tracing board, scissors and calculator. 3. Sample: The sample was divided into four groups (Table 1). Fig. 1: Dental angular parameters CRITERIA FOR SELECTION OF ALL PATIENTS Age: 14 years and above Presence of at least one premolar and molar in each quadrant Presence of all maxillary and mandibular anterior teeth Atleast one maxillary and mandibular molar or premolar on both sides with occlusal contact in centric occlusion. Landmarks used in the Study Sella, nasion, orbitale, ANS (anterior nasal spine), PNS (posterior nasal spine), point A (subspinale), point B (supramentale), pogonion, gnathion, menton, gonion, condylion, porion, point D. SKELETAL LINEAR PARAMETERS Fig. 2: Skeletal linear parameters 1. Anterior upper face height (AUFH): Direct distance between nasion and anterior nasal spine. 2. Anterior cranial base length: Distance between nasion and sella. 3. Mandibular length: Distance between gonion and menton. 4. Anterior lower facial height (ALFH): Direct distance between anterior nasal spine and menton. 5. Ramal length: Distance between articulare and gonion (Fig. 2). 6. ANS-PNS: Distance between anterior and posterior nasal spine. SKELETAL ANGULAR PARAMETERS 1. ANB angle: It is the angle formed by the line N-A and N-B. It relates the anteroposterior position of mandible to the maxilla. Fig. 3: Skeletal angular parameters 256

3 JIOS Fig. 4: Dental linear parameters Fig. 5: Dental linear parameters: (5) Maxillary alveolar basal height (MxABH), (6) maxillary alveolar depth (MxAD), (7) mandibular alveolar basal height (MdABH), (8) mandibular alveolar depth (MdAD). Note: A horizontal line is drawn passing through point A (point 9) parallel to the palatal plane, which intersects the palatal cortical plate at point 10. Two perpendicular lines are drawn from points A and 10 to the palatal plane, thus forming a rectangle. The midpoint of the rectangle is considered the centre point of maxillary alveolus (point 11) Table 1: Sample details Groups Details Criteria for selection Size I Long face male Lower anterior facial height > 80 mm 20 II Short face male Lower anterior facial height < 62 mm 20 III Long face female Lower anterior facial height > 73 mm 20 IV Short face female Lower anterior facial height < 58 mm Mandibular plane angle: This is an angle formed between the FH plane and mandibular plane (Go-Me). This angle gives the inclination of the mandible to the anterior cranial base. 3. Basal plane angle: This is an angle formed between the palatal plane and the mandibular plane (Fig. 3). DENTAL LINEAR PARAMETERS Landmark 12 midpoint of alveolar meatus of maxillary central incisor (Fig. 5), Landmark 17 midpoint of alveolar meatus of mandibular central incisor (Fig. 5). 1. Overjet: This is determined by measuring the horizontal line drawn from incisal edges of maxillary incisor to mandibular incisor. 2. Overbite: This is determined by measuring the vertical line drawn from incisal edges of maxillary incisor to mandibular incisor. 3. The posterior dental maxillary vertical height: It is a perpendicular line from the maxillary mesiobuccal cusp tip to the nasal floor. 4. The posterior dental mandibular vertical height: It is the perpendicular length of a line through the mandibular first molar mesiobuccal cusp tip to mandibular plane. 5. Maxillary incisal alveolar basal height (MxABH): Distance between midpoint of alveolar meatus of maxillary central incisor and intersection between palatal plane and maxillary alveolar axis. 6. Maxillary alveolar depth (MxAD): Shortest line above apex of maxillary central incisors between maxillary midsagittal labial and palatal alveolar cortical bone. 7. Mandibular incisal alveolar basal height (MdABH): Distance between midpoint of alveolar meatus of mandibular central incisor and intersection between symphysial surface and mandibular alveolar axis. 8. Mandibular alveolar depth (MdAD): Shortest line below apex of mandibular central incisors between mandibular midsagittal labial and lingual alveolar cortical bone (Figs 4 and 5). DENTAL ANGULAR PARAMETERS 1. Maxillary incisor inclination: It is the angle formed between the axis of most prominent maxillary central incisor and a line from nasion to point A. 2. Mandibular incisor inclination: It is the angle formed between the axis of most prominent mandibular central incisor and line from nasion to point B. Descriptive data that included mean, standard deviation (SD) and range values were calculated for each group. The differences in skeletal and dentoalveolar parameters between The Journal of Indian Orthodontic Society, October-December 2013;47(4):

4 Bhumi Narendra Modi et al 258 Table 4: Comparison between long and short face women Parameters Long face Short face Mean difference *p-value Sig N-ANS >0.05 NS ANS-Me <0.001 HS N-S <0.05 S Ar-Go >0.05 NS Go-Me >0.05 NS ANS-PNS <0.001 HS ANB(0) <0.05 S BP angle <0.001 HS MP angle <0.001 HS OJ >0.05 NS OB >0.05 NS MxABH <0.001 HS MxABD <0.001 HS MdABH <0.001 HS MdABD <0.001 HS 1-NA >0.05 NS 1-N _ B <0.001 HS MxMH <0.001 HS MdMH <0.001 HS HS: Highly significant; S: Significant; NS: Not significant Table 3: Comparison between long and short face men (*Student s unpaired t-test) Parameters Long face Short face Mean difference *p-value Sig N-ANS <0.05 S ANS- Me <0.001 HS N-S >0.05 NS Ar-Go >0.05 NS Go-Me >0.05 NS ANS-PNS <0.001 HS ANB(0) >0.05 NS BP angle <0.001 HS MP angle <0.001 HS OJ >0.05 NS OB <0.001 HS MxABH <0.001 HS MxABD <0.05 S MdABH <0.001 HS MdABD <0.001 HS 1-NA >0.05 NS 1-N _ B <0.05 NS MxMH <0.001 HS MdMH <0.001 HS HS: Highly significant; S: Significant; NS: Not significant; *p < 0.05 Table 2: Descriptive values for long and short faces Parameters Long face (men) Short face (men) Long face (women) Short face (women) Mean SD Mean SD Mean SD Mean SD N-ANS ANS-Me N-S Ar-Go Go-Me ANS-PNS ANB(0) BP angle MP angle OJ OB MxABH MxABD MdABH MdABD NA _ -NB MxMH MdMH

5 JIOS Table 5: Regression model for long face (*p < 0.01 sig.) Overbite as dependent variable Predictor Multiple R 2 Change in R 2 F change* Beta ANS-Me MdABH BP angle _ - NB MxABH ANS-PNS Table 6: Regression model for short face Overbite is dependent variable Predictor Multiple R 2 Change in R 2 F change* Beta ANB OJ NB MxABH *p < 0.01 significant the short face and long face subjects were assessed using t- tests for men and women separately. Regression analysis was then done to investigate the influence of various parameters on overbite. A p-value of less than 0.05 was considered as statistically significant difference. RESULTS The results have been tabulated and presented as Tables 2 to 6. DISCUSSION Growth is a process requiring intimate morphogenic interrelationships among all of its components. This means that the various parts developmentally merge into a functional whole, with each part complementing the other as they all grow and function together. 4 Orthodontists have investigated the relationship between dental occlusion and skeletal balance of the face. However, as the most popular classification of malocclusion introduced by Angle was defined in the anteroposterior dimension, it was not surprising that most orthodontists looked at malocclusion in that dimension. By comparison, little work had been done in the vertical aspect of malocclusion. 5 It was FF Schudy 6 who stated that we must consider, understand and appreciate the value of vertical growth as it relates to anteroposterior growth. He said Growth of the dentofacial complex does not proceed strictly vertically and anteroposteriorly, these two factors should be considered not as allied but as opposing forces, each vying for the control of pogonion. Problems in the vertical dimension include open bite and deep bite malocclusions. They can be dentoalveolar or skeletal in nature. 1 Vertical dysplasias mainly due to skeletal components are termed short face syndrome and long face syndrome or hypodivergent and hyperdivergent facial types respectively. 7,8 Subjects with vertical dysplasia often deviate in underlying skeletal pattern. 9,10 However, a normal overbite can be attained and maintained as a result of dentoalveolar compensation. 3 These compensatory variations include dentoalveolar height and proclination or retroclination of the maxillary and mandibular incisors. 11 There has been conflicting literature on the parameters which will influence the overbite and to what extent can the compensations mask the discrepancy in the vertical plane. Therefore, there was a need for a study to investigate the influence of skeletal and dentoalveolar parameters on overbite in long-face and short-face individuals and to evaluate whether natural development in an untreated subject can compensate for severe vertical skeletal dysplasia and still render a normal incisor overbite in the present population sample. This study was done on 80 subjects, where the subjects were divided into short and long faces, based on their lower anterior facial height and each group was further subdivided on gender basis. In the present study, it was noted, that in both males and females, the lower anterior facial height showed highly significant differences, with the values being higher in the long face group. The fact that the upper facial height is not necessarily increased in long face shows that not all long faces have a component of vertical maxillary excess in them. The long face could have been due to the inherent growth pattern of the mandible itself, or due to inferior rotation of the posterior maxilla or due to the supraeruption of the posterior teeth. 10 The Journal of Indian Orthodontic Society, October-December 2013;47(4):

6 Bhumi Narendra Modi et al The ramal length did not show any significant differences between the short face and long face groups, this is in contradiction to Isaacson study. 12 This reflects that there can be a normal growth of the ascending ramus which can in fact help in getting a positive overbite by rotating the mandible in a counterclockwise direction but the divergency of skeletal bases and the increased posterior dentition height could have an upper hand and this can result in a long face. Thus, not all long faces have reduced ramal height. The mandibular length in both the groups did not show any significant difference. This was in agreement with the study done by Sassouni and Nanda. 5 Even though the mandibular length in both groups is same, in long face the backward rotating mandible moves pogonion backward and downward giving a less prominent chin 12 and creating an illusion that the mandible is deficient in length. In this study, it was found that the basal plane in low angle cases was significantly reduced as compared to in high angle irrespective of the gender. This was in agreement with the study done by Nanda. 10 This showed that the low angle group is more susceptible to develop a deep bite, and high angle susceptible to open bite. 13 The mandibular plane angle showed highly significant differences in both groups. The mandibular plane angle would also depend on ramal height. In long face individuals, if the ramal height is increased then there can be a possibility of getting a normal mandibular plane angle, 7 similarly in shortface, one group can be characterized by a short ramus and a slightly reduced or normal mandibular plane angle and the other group by a long ramus height and an extremely low mandibular plane angle. 8 Bjork 14 believed that there were lot of remodeling changes in the lower border of the mandible and this could mask the underlying skeletal discrepancy, and thus the angle may not reveal a true picture. In the present study, as the ramal height did not show significant differences and only extremes of short and long faces were taken, the remodeling changes as suggested by Bjork may not have totally masked the underlying skeletal dysplasia. In this study, the vertical height of maxillary and mandibular molars were significantly more in long face as compared to the short face group. The molars can then act as a fulcrum resulting in backward rotation of mandible and a long face; this is more pronounced in nongrowing individuals. 10 This difference in posterior dentoalveolar development could be associated with weaker musculature in high angle cases as opposed to stronger musculature in low angle groups as suggested by Möller 15 and Ingervall. 16 In this study, it was observed that the upper incisor to NA did not show any significant difference. However, the lower incisor to NB angle was more in long face; indicating proclination of lower incisors. This was in contrary to Bjork findings. 12 This difference could be because the long face group had a sagittal component of Class II malocclusion also and as a means of natural compensation, the lower incisors could have proclined. Thus, it is always prudent to consider the vertical and sagittal components of malocclusion together. In the long face group, the strongest predictor of overbite was lower face height, followed by mandibular incisal alveolar height, basal plane angle and lower incisor inclination. The regression equation showed that lower facial height more than mm, would lead to an open bite, unless the mandibular alveolar height also increased. In the short face group, the regression equation showed that the most important predictor of overbite was ANB angle, followed by overjet, lower incisor inclination and maxillary alveolar basal height. This shows that in short face group, the sagittal malocclusion plays a major role. The lower anteriors could have thus supraerupted as there was no positive contact with the maxillary incisors due to increased overjet and this could have also caused bite deepening. CONCLUSION The present study revealed that not all short faces had deep bite and, similarly, not all long faces presented with an open bite. There are many factors which determine the overbite, like the anterior lower facial height, the inherent growth pattern of the mandible, the posterior dentition eruption and the lower incisor inclination. In long face individuals, the most important factor governing overbite is the lower anterior facial height and the mandibular alveolar process can to some extent compensate for this increase and still render a normal overbite. In short face individuals, the overjet and the ANB angle were the factors governing overbite. It was also observed that compensations in vertical plane in the form of supraeruption of the anterior dentition could make the alveolar process narrow and thus impose limitations on sagittal and transverse corrections. Thus, the treatment plan should keep in mind correction in all the three planes of space. REFERENCES 1. McNamara AJ, Brudon WL. Orthodontics and dentofacial orthopedics. Needham Press, Inc Mirzen AZ, Meliha R. 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