Correcting the Class II subdivision malocclusion

Asymmetry in Class II subdivision malocclusion: Assessment based on 3D surface models

INTRODUCTION

There is currently no consensus in the literature whether the aetiology of a Class II subdivision is dental, skeletal or both. The aim of this study was to identify and quantify skeletal and dental asymmetries in Class II subdivision malocclusions.

METHODS

CBCTs from 33 Class II subdivision malocclusion patients were used to construct 3D volumetric label maps. Eighteen landmarks were identified. The original scan and associated 3D volumetric label map were mirrored. Registration of the original and mirrored images relative to the anterior cranial base, maxilla and mandible were performed. Surface models were generated, and 3D differences were quantified. Statistical analysis was performed.

RESULTS

Anterior cranial base registration showed significant differences for fossa vertical difference, fossa roll, mandibular yaw, mandibular lateral displacement and lower midline displacement. Regional registrations showed significant differences for antero-posterior (A-P) mandibular length, maxillary roll, A-P maxillary first molar position, maxillary first molar yaw and maxillary first molar roll. Class II subdivision patients also show an asymmetric mandibular length as well as an asymmetric gonial angle. Moderate correlations were found between the A-P molar relationship and fossa A-P difference, mandibular first molar A-P difference, maxillary first molar A-P difference and maxillary first molar yaw.

CONCLUSIONS

This study suggests that Class II subdivisions can result from both significant skeletal and dental factors. Skeletal factors include a shorter mandible as well as posterior and higher displacement of the fossa on the Class II side, resulting in mandibular yaw. Dental factors include maxillary and mandibular first molar antero-posterior asymmetry.

Invisible treatment with lingual appliance for the correction of an adult class II subdivision with asymmetrical Wilson and Spee curves: A case report

This article describes a class II subdivision malocclusion successfully treated by an invisible lingual appliance. The combination of en-masse distalization by interradicular palatal mini-screws and inner unilateral class II auxiliaries, first by intermaxillary elastic, later by a class II coil spring, resulted in a dento-alveolar correction, allowing one to maintain the appliance completely invisible. At the same time, the inclination of buccal sectors was normalized by a correct torque expression with set-up overcorrections, resulting in a significant improvement of the buccal corridors. This case report demonstrates the possibility of successfully solving class II division 2 subdivision malocclusion in adult patients without surgery by means of a completely invisible appliance. It also demonstrates that correct levelling and torque expression, for the correction of asymmetrical Spee and Wilson curves, are achievable with an accurate set-up planning. On the other hand, it underlines the necessity of mini-screws, auxiliaries and set-up overcorrections in order to obtain the best results.

Asymmetric dental arch treatment with Forsus fatigue appliances: Long-term results

OBJECTIVES

To investigate the treatment efficacy and follow-up stability of the asymmetric Forsus appliance by evaluating longitudinal changes in dental arch asymmetry on digital dental models from 21 patients.

MATERIALS AND METHODS

Maxillary and mandibular reference lines were used for measurements of intra-arch asymmetry at pretreatment (T1), posttreatment (T2), and 4.2 years after treatment (T3). Maxillary and mandibular measurements were performed relative to the dental midline and anterior reference line on digital dental models. To determine the amount of asymmetry between the Class I and Class II sides of a given arch, all maxillary and mandibular parameters were measured on each side of the model separately. Repeated-measures analysis of variance/paired sample t-tests were performed to evaluate dental arch asymmetries at the P < .05 level.

RESULTS

The alveolar transverse dimensions of the posterior segment of both arches were increased during treatment (P < .05) and remained stable during the retention period. Class II subdivision malocclusion was caused by distal positioning of the mandibular canine, premolars, and first molar on the Class II side (P < .05). Asymmetry was resolved by treatment with asymmetric Forsus appliances. The resolved asymmetry remained stable over the long term. There were no significant differences between T2 and T3 (P > .05).

CONCLUSIONS

The asymmetric Forsus appliance can be used to treat dental arch asymmetry in patients with Class II subdivision malocclusions.

Dentoskeletal and soft tissue changes in class II subdivision treatment with asymmetric extraction protocols

Background

This study cephalometrically compared the dentoskeletal and soft tissue changes consequent to one and three-premolar extraction protocols of class II subdivision malocclusion treatment.

Methods

A sample of 126 lateral cephalometric radiographs from 63 patients was selected and divided into two groups. Group 1 consisted of 31 type 1 class II subdivision malocclusion patients treated with asymmetric extractions of two maxillary premolars and one mandibular premolar on the class I side, with an initial mean age of 13.58 years. Group 2 consisted of 32 type 2 class II subdivision malocclusion patients treated with asymmetric extraction of one maxillary first premolar on the class II side, with an initial mean age of 13.98 years. t test was used for intergroup comparison at the pre- and posttreatment stages and to compare the treatment changes.

Results

Group 1 had greater maxillomandibular sagittal discrepancy reduction and greater maxillary first molar extrusion. Group 2 had mandibular incisor labial inclination and protrusion, and group 1 had mandibular incisor lingual inclination and retraction. Maxillary molar asymmetry increased in group 2, while mandibular molar asymmetry increased in group 1.

Conclusions

The treatment changes produced by these two class II subdivision protocols are different to adequately satisfy the different needs for types 1 and 2 class II subdivision malocclusions.

Effects of unilateral premolar extraction treatment on the dental arch forms of Class II subdivision malocclusions

INTRODUCTION

A retrospective study evaluating posttreatment symmetry in dental arch form and midlines was carried out in Class II subdivision patients treated with unilateral and bilateral maxillary premolar extractions.

METHODS

Using Geomagic (version 14; Geomagic, Research Triangle Park, NC) and MATLAB (version 8.4; MathWorks, Natick, Mass) software, best-fit curves expressed as quartic polynomials were generated for 13 Class II subdivisions treated with unilateral extractions and 20 treated with bilateral maxillary premolar extractions. Transverse and sagittal measurements were recorded to assess symmetry. Dental models were superimposed on constructed reference planes to generate average posttreatment arches. Statistical comparisons were performed with the significance level set at P ≤0.05.

RESULTS

The unilateral extraction group showed significant differences in transverse arch forms between the right and left sides in the anterior, anterior-middle, and middle segments of the arch, and all regions other than the posterior segment in the sagittal dimension. Significant differences were found between groups in the anterior and anterior-middle segments of the arch transversely, the middle and middle-posterior segments sagittally, and the midline deviation relative to the midsagittal plane. Superimposed average arches showed similar results.

CONCLUSIONS

Unilateral maxillary extraction treatment generally results in a narrower and more posteriorly displaced arch form on the extraction side, with a deviated maxillary midline toward the extraction side of the arch.

Dental, skeletal asymmetries and functional characteristics in Class II subdivision malocclusions

Treatment outcomes of Angle Class II subdivision malocclusions may be compromised because of the uncertainty of the aetiology. Previous studies have reported controversial ideas about the origins, but the existence of a primary contributor still remains unknown. Functional factors have been mentioned as a probable cause, but until now, there have been no supporting data. This study was a cross-sectional investigation of the characteristics of Angle Class II subdivision malocclusion, including dental, skeletal and functional factors, by comparison of the subdivision group and the normal occlusion group. The evaluations of dental and skeletal asymmetries of both groups were carried out by cone-beam computed tomography (CBCT) and analysis of dental casts. The functional deviations were evaluated by cast mounting and measuring. In the subdivision group, the asymmetric position of the glenoid fossa was found to be the most significant skeletal asymmetry. No dentoalveolar asymmetry was found in this group. The most important finding was that, in subdivision malocclusions, functional deviation resulting in pseudoasymmetry occurred in 32.86% of the study participants. This deviation is probably related to the disharmonious arch width between maxillary and mandibular dental arches in the premolar section. The origin of Angle Class II subdivision malocclusion is multifactorial, with dental, skeletal and functional factors included. Functional deviation occurs, probably due to dental arch width disharmony. Asymmetric position of the glenoid fossa may account for most of the skeletal asymmetry.

Stability of class II subdivision malocclusion treatment with 3 and 4 premolar extractions

BACKGROUND

The purpose of this study was to compare the occlusal stability of class II subdivision malocclusion treatment with 3 and 4 first premolar extractions. A sample of 156 dental casts from 52 patients with class II subdivision malocclusion was divided into two groups according to the extraction protocol. Group 1 comprised 24 patients treated with 3 premolar extractions and group 2 included 28 patients treated with 4 premolar extractions.

METHODS

Peer assessment rating (PAR) indexes were measured on the dental casts obtained before (T1) and after treatment (T2) and at a mean of 6.9 years after the end of treatment (T3). The groups were matching regarding sex distribution, pretreatment, posttreatment and long-term posttreatment ages, and treatment and long-term posttreatment times. They were also comparable concerning the initial malocclusion severity and the occlusal results at the end of treatment. Stability evaluation was calculated by subtracting the posttreatment from the long-term posttreatment index values (T3 - T2). T tests were used to compare the amount and percentage of long-term posttreatment changes.

RESULTS

There were no intergroup differences regarding the amount and percentage of long-term posttreatment changes.

CONCLUSION

Treatment of class II subdivision malocclusion with 3 and 4 premolar extractions have a similar long-term posttreatment occlusal stability.

Evaluation of skeletal and dental asymmetries in Angle Class II subdivision malocclusions with cone-beam computed tomography

INTRODUCTION

The purpose of this study was to determine whether Angle Class II subdivision malocclusions have skeletal or dental asymmetries between the Class II and Class I sides.

METHODS

A sample of 54 untreated Angle Class II subdivision patients with pretreatment photos and cone-beam computed tomography (CBCT) scans was used. The photos were used to identify the Class II subdivision malocclusion and to record the amount of crowding per quadrant. Landmarks were plotted on each CBCT volume so that direct 3-dimensional measurements could be made to compare the positions and dimensions of the skeletal and dental structures on the Class II side vs the Class I side.

RESULTS

Significant differences were found for 2 skeletal measurements: the position of the maxilla relative to the cranial base, and the mandibular dimension from the mandibular foramen to the mental foramen. Statistically significant dental differences were found for the position of the mandibular first molars and canines in relation to the maxilla and the mandible. Statistically significant differences were found for the maxillary first molars and canines in relation to the mandible.

CONCLUSIONS

There were significant skeletal and dental differences between the Class I and Class II sides. The dental asymmetries accounted for about two thirds of the total asymmetry.

Class II subdivision treatment with the Herbst appliance

OBJECTIVE

To assess the effectiveness of Class II subdivision Herbst nonextraction treatment and its short-term stability retrospectively.

MATERIALS AND METHODS

Twenty-two Class II subdivision (SUB: right-left molar difference ≥0.75 cusp width) and 22 symmetric Class II patients (SYM: ≥0.75 cusp width bilaterally) were matched according to gender and pretreatment handwrist radiographic stage. The mean treatment duration of the Herbst and subsequent multibracket phase was 8 months and 14 months, respectively. The mean retention period amounted to 36 months. Dental casts from before treatment (T1), after Herbst treatment (T2), after Multibracket treatment (T3), and after retention (T4) were evaluated.

RESULTS

A bilateral Class I or super Class I molar relationship was seen in 72.7% (SUB) and 77.3% (SYM) at T3. The corresponding values at T4 were 63.7% (SUB) and 72.7% (SYM). A unilateral or bilateral Class III molar relationship was more frequent in the SUB group (T3: +4.6%; T4: +13.6%). For overjet, similar mean values were seen in both groups after treatment (T3: SUB, 2.7 mm; SYM, 2.3 mm) and after retention (T4: SUB, 3.0 mm; SYM, 3.4 mm). This was also true for the midline shift (T3: SUB, -0.4 mm; SYM, 0.0 mm; T4: SUB, -0.3 mm; SYM, 0.0 mm).

CONCLUSION

Class II subdivision Herbst treatment was successful similarly to symmetric Class II Herbst treatment. However, a slight overcompensation of the molar relationship (Class III tendency) was more frequent in the subdivision patients (original Class I side).

Orthodontic-orthognathic surgical treatment in a patient with Class II subdivision malocclusion: occlusal plane alteration

Despite the different orthodontic treatment options for patients with Class II subdivision malocclusions, the involvement of the skeletal structures is significant. It is desirable to combine orthodontic and surgical treatment to achieve a stable and better esthetic result, as illustrated in this case report. The occlusal plane was canted to the right as a part of the patient's facial asymmetry. Consequently, a 3-mm differential impaction of the maxilla on the left side allowed occlusal plane leveling. Mandibular rotation with advancement on the right side corrected the right Class II malocclusion. The successful attainment of the treatment goals was accomplished through teamwork and integration between the orthodontist and the maxillofacial surgeon.

Má oclusão Classe II, 2ª divisão de Angle com sobremordida exagerada e discrepância acentuada

Este artigo relata o tratamento de uma jovem paciente, com 13,8 anos de idade, que apresentava uma má oclusão Classe II, segunda divisão de Angle, retenção prolongada de dentes decíduos, mordida cruzada dentária, sobremordida exagerada, dentre outros desvios da normalidade. Inicialmente, a abordagem ortodôntica envolveu uma expansão da maxila, seguida pelo uso do aparelho extrabucal de Kloehn e aparelhagem ortodôntica fixa. O resultado obtido demonstra a importância de um diagnóstico e planejamento criteriosos, bem como a necessidade de colaboração do paciente durante o tratamento ortodôntico. Este caso clínico foi apresentado à Diretoria do Board Brasileiro de Ortodontia e Ortopedia Facial (BBO), representando a categoria livre, como parte dos requisitos para a obtenção do título de diplomado pelo BBO.

Association between mandibular asymmetry and occlusal asymmetry in young adult males with class III malocclusion

OBJECTIVE

Our aim was to assess the association between mandibular asymmetry and sagittal and transverse occlusal asymmetry in young adult males with class III malocclusion. Our hypotheses were that (1) mandibular asymmetry increases with increasing mandibular length and (2) occlusal asymmetry is correlated with mandibular asymmetry.

MATERIAL AND METHODS

On lateral cephalograms of 54 subjects, skeletal class and mandibular length were measured. Mandibular asymmetry was evaluated on orthopantomograms as right-left difference between condylar or ramus heights. Occlusal asymmetry was assessed on dental casts by differences between right and left canine and molar relationship, anterior and posterior crossbite as well as midline deviation.

RESULTS

Mandibular asymmetry was significantly correlated with sagittal and transverse occlusal asymmetry (p < 0.05), but not with mandibular length (p > 0.05). Condylar asymmetry due to a longer condyle on one side was correlated with asymmetric aggravation of canine and molar class III on the ipsilateral side (r = -0.53 and -0.62, respectively). In contrast, ramus asymmetry was related to contralateral aggravation of canine and molar class III relationships (r = 0.27 and 0.29, respectively). Correlations existed between asymmetry in total height of the condyle and ramus and asymmetric aggravation of anterior crossbite (r = -0.33), posterior crossbite (r = -0.30) and lower midline deviation (r = -0.27) to the contralateral side (p < 0.05).

CONCLUSIONS

Mandibular asymmetry is associated with occlusal asymmetry, especially in the sagittal plane. Condylar asymmetry had 28% and 38% of variance in common with sagittal canine and molar asymmetry, respectively. Asymmetry in total height of the condyle and ramus was related to transverse occlusal asymmetry.

Treatment of a Class II subdivision malocclusion with multiple congenitally missing teeth

This case report describes the treatment of a patient with a Class II Division 1 subdivision right malocclusion with 8 congenitally missing teeth, incompetent lips, and incisor protrusion. The treatment plan included extractions and space closure with retraction of the anterior teeth; symmetric mechanics were used in the mandibular arch and asymmetric mechanics in the maxillary arch. Because of the mechanics used, some midline deviations were expected. Knowledge of diagnosis and treatment planning of asymmetric malocclusions and dental esthetics are essential for success when correcting asymmetic problems, but, even so, small clinical compromises should be expected.

An orthodontic-surgical approach to Class II subdivision malocclusion treatment

Despite the different orthodontic approaches to Class II subdivision malocclusions one has also to consider the skeletal components before undertaking any treatment protocol. Significant involvement of the skeletal structures may require a combined surgical orthodontic treatment, which has remained stable for more than four years, as illustrated in this case report.

Mandibular Asymmetry in Class II Subdivision Malocclusion

Objective: To evaluate the condylar and ramal mandibular asymmetry in a group of patients with Class II subdivision malocclusion to identify possible gender differences between male and female subjects.

Materials and Methods: Mandibular asymmetry measurements (condylar, ramal, and condylar-plus-ramal asymmetry values) were performed on the panoramic radiographs of 80 subjects (34 male and 46 female). The study group consisted of 40 Class II subdivision patients (18 male and 22 female; mean age 14.53 ± 3.14 years). The control group consisted of 40 subjects with normal occlusion (16 male and 24 female; mean age 14.43 ± 3.05 years). The Kruskal-Wallis test was used to determine the possible statistically significant differences between the groups for condylar, ramal, and condylar-plus-ramal asymmetry index measurements. Identified differences between groups were further analyzed using the Mann-Whitney U-test at the 95% confidence interval (P &lt; .05).

Results: No gender-related difference was found for any of the asymmetry indices. Comparison of condylar, ramal, and condylar-plus-ramal asymmetry index values and gonial angle measurements for Class I and Class II sides in the Class II subdivision group and for right and left sides in the Class I group showed no statistically significant differences. However, the Class II subdivision group has longer values for condylar, ramal, and condylar-plus-ramal height measurements and only these differences were statistically significant (P &lt; .001).

Conclusions: Except for condylar ramal and condylar-plus-ramal height measurements, Class II subdivision patients have symmetrical condyles when compared to normal occlusion samples according to Habbet's mandibular asymmetry indices.