Class II subdivision malocclusion types and evaluation of their asymmetries

Class II subdivision treatment and stability with asymmetric Herbst appliance: A case report

Non-surgical treatment of Class II subdivision may involve complex mechanics or asymmetric tooth extraction in its resolution. This report demonstrates the result and the short-term stability of Class II subdivision treated with asymmetrically installed Herbst appliance followed by conventional fixed orthodontic appliance. The approach allowed the correction of the unilateral Class II molar relationship and increased overjet, as well as the deviation of dental midlines, with improvement in lip posture and facial profile. The results remained stable two years after treatment, confirming the treatment success.

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.

Third molar angulation and retromolar space after functional orthodontic treatment : Evaluation of panoramic radiographs after monoblock or Herbst appliance

PURPOSE

The aim of this respectively cohort study was to evaluate the lower second and third molars and canine angulations, retromolar space and occlusal relationships after functional orthodontic treatments with the monoblock or Herbst appliance using panoramic radiographs.

METHODS

Pre- and posttreatment cephalometric and panoramic radiographs of 133 patients (mean age 13.89 ± 1.14 years) treated non-extraction with monoblock (n: 44), Herbst (n: 45) and fixed orthodontic appliances (control group; n: 44) were included to the study. Dental and skeletal measurements were performed on cephalometric radiographs. The angle between the third and second molars, and canines with the lower border of the mandible and the occlusal plane, gonial angle, the angle between the third and second molars and the retromolar space width were assessed on pre- and posttreatment panoramic radiographs. Paired and independent t tests were used for the statistical analysis of the data for intragroup and intergroup comparisons.

RESULTS

Functional treatment with both the monoblock and the Herbst appliances resulted in improvement of skeletal class II relationships. Retromolar space significantly increased in the functional appliance groups compared to the control group (p ≤ 0.001), but improvement of the angulations of posterior teeth was significant only in the monoblock group (p ≤ 0.001).

CONCLUSION

While both the Herbst and monoblock appliances led to an increase in retromolar space, monoblock treatment resulted in more favorable angulation of the third molars compared to the Herbst treatment.

Biomechanically and Periodontally-Based Orthodontic Treatment of a Patient with Upper Canine Affected by External Cervical Resorption (ECR): A Case Report

(1) Background: Orthodontic treatment may be a potential predisposing factor for ECR. The affected tooth goes to ankylosis, which could lead to a malocclusion. Although teeth severely affected by ECR (class IV Heithersay) are usually extracted, this case report aims to present the use of an ECR class IV upper canine, both as ankylosed to solve the malocclusion and the occlusal plane canting, as well as not ankylosed to correct its ridge defect with orthodontic extrusion. (2) Methods: A 14-year-old male, complaining of an ugly smile and a failed orthodontic attempt to recover an impacted canine, was referred to the orthodontic clinic. He was diagnosed with class II right subdivision, midline deviation, both upper and lower occlusal plane canting, and an upper left canine, previously impacted, showing ECR class IV. The treatment first included canting resolution with a cantilever and a spring, exploiting the anchorage offered by the ankylosed ECR canine. Then, a coronectomy, endodontic treatment, and orthodontic extrusion of that canine were performed to obtain the implant site development. (3) Results: Clinical and radiographic outcomes showed normocclusion and better bony conditions for safer implant placement in the aesthetic zone. (4) Conclusions: The high aesthetics and the periodontal and bony conditions obtained are probably not achievable by other therapeutic alternatives.

New Trend in Treating Class II Division 2 Subdivision: A Case Report

Class II correction in non-growing patients will always pose a challenge in treatment, especially in a subdivision condition where one quadrant will exhibit class II molar and canine, and the other side will exhibit class I. In such a scenario, a contemporary extraction protocol will face a challenge in symmetric space closure. This case report describes the management of class II subdivision malocclusion by the latest approach, i.e., extraction of a single premolar. At the end of the treatment, midlines were corrected and good functional class I canine relations on both sides were established.

The association between dental and facial symmetry in adolescents

INTRODUCTION

Facial aesthetics have become one of the most important objectives of orthodontic treatment. The correction of dental arches should be performed in accordance with the face. This study explored the association between occlusal and facial asymmetries in adolescents, particularly emphasizing a Class II subdivision.

METHODS

Eighty-one adolescents (43 males, 38 females) with a median age of 15.9 (interquartile range, 15.17-16.33) years were enrolled. Of these patients, 30 had a Class II subdivision (right side, n = 12; left side, n = 18). Three-dimensional facial scans were analyzed using surface- and landmark-based methods. Chin asymmetry was determined using the chin volume asymmetry score. Three-dimensional intraoral scans were analyzed to assess occlusal asymmetry.

RESULTS

The surface matching scores were 59.0% ± 11.3% for the whole face and 39.0% ± 19.2% for the chin. Chin volume was larger on the right side than on the left side in most patients (n = 51, 63%), and it was associated with a dental midline shift to the corresponding subdivision side. A correlation between dental and facial asymmetries was noted. In addition, the dental midline shifted to the left in patients with a Class II subdivision, regardless of the side, and to the right in those with a symmetrical Class II subdivision. However, several patients did not possess asymmetrical occlusal traits sufficient for statistical analysis.

CONCLUSIONS

Dental asymmetry was weak but significantly correlated with facial asymmetry.

3D Facial Analysis in Class II Subdivision Malocclusion

Background:

Class II subdivision is an asymmetric condition presenting a Class I dental occlusion on one side and a Class II on the contralateral one. It presents a midline deviation that may be caused by a monolateral distalization of the mandible (type 1) or a mesialization of one side of the maxilla (type 2). The evaluation of asymmetry based on 2D radiographic records has been demonstrated to be less accurate than the one made using 3D radiographs.

Objective:

The aim of this work is to evaluate the facial asymmetry in a group of patients with Class II subdivision, compared to patients in Class I without evident asymmetry, by using 3D photographs of the face.

Methods:

32 young adults with Class II subdivision were compared to a group of 32 subjects with bilateral Class I molar relationship. 3D photograph of their face was acquired using a stereophotogrammetric camera (3dMDtrio System-3dMD Atlanta, GA, USA). 3D photographs were imported into the Geomagic Software to create mirror 3D photography. Independent T-tests were made to compare facial asymmetries measured on Class II subdivision group with the Class I group.

Results:

The results show that there is a statistically significant difference in landmarks location between the control group and the experimental group regarding the values measured at the level of the lips and the perioral area. The asymmetry was more marked in patients with mandibular midline deviation. This is in line with previous observations with radiographic investigations.

Conclusion:

For a correct assessment of the asymmetry, a study of 3D photographs cannot replace an evaluation by cone beam, but it can be an important aid to estimate possible asymmetries in the perioral area and in the lip area.

Differences in third molar development and angulation in class II subdivision malocclusions

PURPOSE

To assess and compare the developmental stages and angulations of third molars between the class II and class I sides in class II subdivision malocclusions.

METHODS

This retrospective study was performed using panoramic x‑rays of 38 individuals (mean age: 15.5 years; 24 females, 14 males) with class II subdivision malocclusions, which were further divided into type 1 and 2 subgroups according to midline deviation, and a control group of 42 individuals (mean age: 17.0 years; 30 females, 12 males) with normal occlusion. Third molars were categorized using the developmental stages defined by the Demirjian method. Angles between the third molars and horizontal reference lines and also to the second molars were measured.

RESULTS

No difference was found in developmental stages or angulations between the left and right third molars in the control group. In the class II subdivision malocclusion cases, no difference in third molar developmental stages was observed, but the angle between the long axes of the mandibular third and second molars was significantly greater on the class II side. In the type 2 subgroup, developmental stage of the maxillary third molar was more advanced on the class II side. In both subgroups, the angles of the maxillary third molars' long axis to the interorbital plane differed significantly between the two sides.

CONCLUSION

Class II subdivision malocclusion may cause differences in third molar development and angulations between the two sides. Orthodontic treatment should be planned considering the third molars in this malocclusion.

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.

Cone-beam computed tomographic evaluation of the temporomandibular joint and dental characteristics of patients with Class II subdivision malocclusion and asymmetry

OBJECTIVE

Treating Class II subdivision malocclusion with asymmetry has been a challenge for orthodontists because of the complicated characteristics of asymmetry. This study aimed to explore the characteristics of dental and skeletal asymmetry in Class II subdivision malocclusion, and to assess the relationship between the condyle-glenoid fossa and first molar.

METHODS

Cone-beam computed tomographic images of 32 patients with Class II subdivision malocclusion were three-dimensionally reconstructed using the Mimics software. Forty-five anatomic landmarks on the reconstructed structures were selected and 27 linear and angular measurements were performed. Paired-samples t-tests were used to compare the average differences between the Class I and Class II sides; Pearson correlation coefficient (r) was used for analyzing the linear association.

RESULTS

The faciolingual crown angulation of the mandibular first molar (p < 0.05), sagittal position of the maxillary and mandibular first molars (p < 0.01), condylar head height (p < 0.01), condylar process height (p < 0.05), and angle of the posterior wall of the articular tubercle and coronal position of the glenoid fossa (p < 0.01) were significantly different between the two sides. The morphology and position of the condyle-glenoid fossa significantly correlated with the three-dimensional changes in the first molar.

CONCLUSIONS

Asymmetry in the sagittal position of the maxillary and mandibular first molars between the two sides and significant lingual inclination of the mandibular first molar on the Class II side were the dental characteristics of Class II subdivision malocclusion. Condylar morphology and glenoid fossa position asymmetries were the major components of skeletal asymmetry and were well correlated with the three-dimensional position of the first molar.

Relationship between molar occlusion and masticatory movement in lateral deviation of the mandible

INTRODUCTION

The relationship between molar occlusion and chewing patterns was examined in subjects with laterally deviated mandibles.

METHODS

Twenty-three patients with mandibular deviation from the midline (4 mm or more) and skeletal Class I (0° ≤ANB ≤4°) were divided into 2 groups: normal bite and crossbite. The chewing pattern was classified as normal, reversed, or crossover.

RESULTS

The normal bite group had a normal chewing pattern on the affected side 100% of the time and a reversed chewing pattern on the affected and unaffected sides 0% and 7.2% of the time, respectively. Additionally, the normal bite group showed no evidence of a crossover chewing pattern and also had significantly less axial inclination of the mandibular teeth on the affected side compared with the crossbite group; lingual inclination was also evident. The crossbite group had a normal chewing pattern on the affected and unaffected sides 0% and 55.6% of the time, respectively, and reversed and crossover chewing patterns on the affected side 55.6% and 44.4% of the time, respectively.

CONCLUSIONS

A normal chewing pattern tends to result in lingual axial inclination of the mandibular molars on the affected side, as well as a more consistent chewing pattern.

Analysis of potential dynamic concealed factors in the difficulty of lower third molar extraction

BACKGROUND

The purpose of this study was to identify potential concealed variables associated with the difficulty of lower third molar (M3) extractions.

MATERIAL AND METHODS

To address the research purpose, we implemented a prospective study and enrolled a sample of subjects presenting for M3 removal. Predictor variables were categorized into Group-I and Group-II, based on predetermined criteria. The primary outcome variable was the difficulty of extraction, measured as extraction time. Appropriate univariate and multivariate statistics were computed using ordinal logistic regression.

RESULTS

The sample comprised of 1235 subjects with a mean age of 29.49 +/- 8.92 years in Group-I and 26.20 +/- 11.55 years in Group-II subjects. The mean operating time per M3 extraction was 21.24 +/- 12.80 and 20.24 +/- 12.50 minutes for Group-I and Group-II subjects respectively. Three linear parameters including B-M2 height (distance between imaginary point B on the inferior border of mandibular body, and M2), lingual cortical thickness, bone density and one angular parameter including Rc-Cs angle (angle between ramus curvature and curve of spee), in addition to patient's age, profile type, facial type, cant of occlusal plane, and decreased overbite, were found to be statistically associated ( p < or = 0.05) with extraction difficulty under regression models.

CONCLUSIONS

In conclusion, our study indicates that the difficulty of lower M3 extractions is possibly governed by morphological and biomechanical factors with substantial influence of myofunctional factors.

PRACTICAL IMPLICATIONS

Preoperative evaluation of dynamic concealed factors may not only help in envisaging the difficulty and planning of surgical approach but might also help in better time management in clinical practice.

Class II subdivision treatment with the Forsus Fatigue Resistant Device vs intermaxillary elastics

OBJECTIVE

To compare the effectiveness of comprehensive fixed appliance treatments implemented in combination with Forsus or intermaxillary elastics in Class II subdivision subjects.

MATERIALS AND METHODS

Twenty-eight Class II subdivision patients were allocated to two groups using matched randomization: Forsus group (mean age, 14.19 ± 1.02 years) and elastics group (mean age, 13.75 ± 1.16 years). Patients received fixed appliance therapy in combination with either Forsus or intermaxillary elastics. The study was conducted on lateral cephalograms and digital models acquired before orthodontic treatment and 10-12 weeks after the fixed appliances were removed.

RESULTS

The treatment phase comprising the use of Forsus (4.53 ± 0.91 months) was significantly shorter compared with elastics application (6.85 ± 1.08 months). This was also true for comparing duration of overall comprehensive treatment in both groups. Extrusion and palatal tipping of maxillary incisors and clockwise rotation of the occlusal plane were greater in the elastics group (P < .05). The mandibular incisors were proclined in both groups (P < .001), but no significant difference was observed between groups (P > .05). The mandibular incisors showed intrusion in the Forsus group and extrusion in the elastics group; the difference between groups was significant (P < .05). Overbite was decreased in both groups (P < .001) in similar amounts. Improvement in overjet, mandibular midline deviation, and correction of molar relationship on the Class II side were greater in the Forsus group (P < .05).

CONCLUSION

Forsus is more effective for correcting Class II subdivision malocclusion in a shorter treatment period with minimal patient compliance required.

Efficiency of Class II subdivision malocclusion treatment with 3 and 4 premolar extractions

INTRODUCTION

In this study, we compared the efficiency of Class II subdivision malocclusion treatment with symmetric and asymmetric extractions.

METHODS

A sample of 71 patients with complete Class II subdivision malocclusion was selected: group 1 consisted of 40 patients treated with 4 premolar extractions with an initial mean age of 13.37 years, and group 2 had 31 patients treated with 3 premolar extractions (2 maxillary premolars and 1 mandibular premolar on the Class I side) with an initial mean age of 14.44 years. To compare the efficiency of each treatment protocol, the initial and final occlusal results were evaluated on dental casts with the Peer Assessment Rating occlusal index, and time spent in treatment was calculated from the clinical charts. The amounts of initial and final midline deviation and improvement of midline deviation correction were also evaluated. Efficiency was calculated as the rate between occlusal improvement by the treatment time. The groups were compared with t and Mann-Whitney tests.

RESULTS

The results showed that group 2 had a significantly smaller final amount of midline deviation and a greater correction of midline deviation.

CONCLUSIONS

Treatment efficiency of type 1 Class II subdivision malocclusions with 3 or 4 premolar extractions is similar. However, treatment with 3 premolar extractions provides a better occlusal success rate.

Lateral cephalometric diagnosis of asymmetry in Angle Class II subdivision compared to Class I and II

INTRODUCTION

Lateral cephalometric radiographs are traditionally required for orthodontic treatment, yet rarely used to assess asymmetries.

OBJECTIVE

The objective of the present study was to use lateral cephalometric radiographs to identify existing skeletal and dentoalveolar morphological alterations in Class II subdivision and to compare them with the existing morphology in Class I and II relationship.

MATERIAL AND METHODS

Ninety initial lateral cephalometric radiographs of male and female Brazilian children aged between 12 to 15 years old were randomly and proportionally divided into three groups: Group 1 (Class I), Group 2 (Class II) and Group 3 (Class II subdivision). Analysis of lateral cephalometric radiographs included angular measurements, horizontal linear measurements and two indexes of asymmetry that were prepared for this study.

RESULTS

In accordance with an Index of Dental Asymmetry (IDA), greater mandibular dental asymmetry was identified in Group 3. An Index of Mandibular Asymmetry (IMA) revealed less skeletal and dental mandibular asymmetry in Group 2, greater skeletal mandibular asymmetry in Group 1, and greater mandibular dental asymmetry in Group 3.

CONCLUSION

Both IDA and IMA revealed greater mandibular dental asymmetry for Group 3 in comparison to Groups 1 and 2. These results are in accordance with those found by other diagnostic methods, showing that lateral cephalometric radiography is an acceptable method to identify existing skeletal and dentoalveolar morphological alterations in malocclusions.

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.

Radiographic assessment of lower third molar eruption in different anteroposterior skeletal patterns and age-related groups

OBJECTIVE

To analyze radiographic predictors for lower third molar eruption among subjects with different anteroposterior skeletal relations and of different age groups.

MATERIALS AND METHODS

In total, 300 lower third molars were recorded on diagnostic digital orthopantomograms (DPTs) and lateral cephalograms (LCs). The radiographs were grouped according to sagittal intermaxillary angle (ANB), subject age, and level of lower third molar eruption. The DPT was used to analyze retromolar space, mesiodistal crown width, space/width ratio, third and second molar angulation (α, γ), third molar inclination (β), and gonion angle. The LC was used to determine ANB, angles of maxillar and mandibular prognathism (SNA, SNB), mandibular plane angle (SN/MP), and mandibular lengths. A logistic regression model was created using the statistically significant predictors.

RESULTS

The logistic regression analysis revealed a statistically significant impact of β angle and distance between gonion and gnathion (Go-Gn) on the level of lower third molar eruption (P < .001 and P < .015, respectively). The retromolar space was significantly increased in the adult subgroup for all skeletal classes. The lower third molar impaction rate was significantly higher in the adult subgroup with the Class II (62.3%) compared with Class III subjects (31.7%; P < .013).

CONCLUSION

The most favorable values of linear and angular predictors of mandibular third molar eruption were measured in Class III subjects. For valid estimation of mandibular third molar eruption, certain linear and angular measures (β angle, Go-Gn), as well as the size of the retromolar space, need to be considered.

Frequency evaluation of different extraction protocols in orthodontic treatment during 35 years

BACKGROUND

Studies that show frequencies of different orthodontic treatment protocols can be used as valuable parameters in the interpretation of treatment tendency with time. The purpose of this retrospective study was to evaluate all orthodontic treatment planning conducted at the Orthodontic Department at Bauru Dental School, University of São Paulo, Brazil, since 1973, in order to investigate extraction and non-extraction protocol frequencies selected at each considered period.

METHODS

The sample comprised 3,413 records of treated patients and was evaluated according to the protocol choice, divided into 10 groups: Protocol 0 (non-extraction); Protocol 1 (four first premolar extractions); Protocol 2 (two first maxillary and two second mandibular premolars); Protocol 3 (two maxillary premolar extractions); Protocol 4 (four second premolars); Protocol 5 (asymmetric premolar extractions); Protocol 6 (incisor or canine extractions); Protocol 7 (first or second molar extractions); Protocol 8 (atypical extractions) and Protocol 9 (agenesis and previously missing permanent teeth). These protocols were evaluated in seven 5-year intervals: Interval 1 (1973 to 1977); Interval 2 (1978 to 1982); Interval 3 (1983 to 1987); Interval 4 (1988 to 1992); Interval 5 (1993 to 1997); Interval 6 (1998 to 2002); Interval 7 (2003 to 2007). The frequency of each protocol was compared between the seven intervals, using the proportion test (P < 0.05).

RESULTS

The results showed that 10 protocol frequencies were significantly different among the 7 time intervals.

CONCLUSIONS

The non-extraction protocol frequency increased gradually with consequent reduction of extraction treatments. The four premolar extraction protocol frequency decreased gradually while the two maxillary premolar extraction protocol has maintained the same frequency of indications throughout time.

Longitudinal evaluation of dental arch asymmetry in Class II subdivision malocclusion with 3-dimensional digital models

INTRODUCTION

Class II subdivision malocclusions with their asymmetric occlusal relationships often pose treatment difficulties. The aim of this study was to evaluate the longitudinal changes of dental arch asymmetry in untreated subjects with Class II subdivision malocclusion.

METHODS

From 706 files from the University of Michigan Growth Study, longitudinal records of 17 untreated subjects with Class II subdivision malocclusion were included this study. Dental arch changes at 3 consecutive longitudinal intervals, defined by the cervical vertebral maturation method, were analyzed on digital dental models. The average ages of the subjects were 12.4, 15.1, and 19.1 years at the 3 time periods, respectively. Maxillary and mandibular reference lines were constructed and used for the intra-arch asymmetry measurements. The Friedman test and analysis of variance with repeated measures were used to determine dental arch asymmetries at the P <0.05 level.

RESULTS

All subjects were found to have a type 1 Class II subdivision malocclusion characterized by distal positioning of the mandibular first molar on the Class II side. No statistically significant intra-arch asymmetry changes were found for the maxillary and mandibular dental arches in any time period. Between the baseline and the final follow-up, the data indicated decreases in maxillary and mandibular intercanine arch widths and arch lengths symmetrically.

CONCLUSIONS

The results of this study indicate that the dental arch asymmetry in patients with Class II subdivision malocclusions did not improve or worsen with growth.

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.

Asymmetry assessment using cone beam CT. A Class I and Class II patient comparison

OBJECTIVE

To estimate possible differences in skeletal asymmetry between patients with skeletal Class I and skeletal Class II relationships.

MATERIALS AND METHODS

Cone beam computed tomography (CBCT) images were examined from 70 consecutive patients who presented for orthodontic care and fit the inclusion criteria. Asymmetry was quantified using an asymmetry index developed by Katsumata et al. Anatomic landmarks were defined and reference planes were established to determine the asymmetry of the landmarks using a constructed coordinate plane system. Thirty randomly selected patients were reanalyzed to assess the reliability of the method.

RESULTS

Statistical analysis did not find any significant relationship between asymmetry and A-P skeletal relationship for any of the landmarks. Asymmetry index scores were reproducible within a certain range of agreement for each landmark.

CONCLUSIONS

Based on this study, the discrepant jaw growth resulting in a Class II skeletal pattern results in no more skeletal asymmetry than Class I skeletal patterns.

Determination of midsagittal plane for evaluation of facial asymmetry using three-dimensional computed tomography

PURPOSE

The aim of the present study was to investigate the disagreement of cephalometric analysis depending on the reference determination of midsagittal plane on three-dimensional computed tomography.

MATERIALS AND METHODS

A total of 102 young women with class III dentofacial deformity were evaluated using three-dimensional computed tomography. The cranial and facial midsagittal planes were defined and the amounts of jaw deviation were calculated. The amounts of jaw deviation were compared with paired t-test (2-tailed) and Bland-Altman plot was drawn.

RESULTS

The landmark tracing were reproducible (r≥.978). The jaws relative to the cranial midsagittal plane were 10-17 times more significantly deviated than to the facial midsagittal plane (P<.001). Bland-Altman plot demonstrated that the differences between the amounts of jaw deviation from two midsagittal planes were not normally distributed versus the average of the amounts of jaw deviation from two midsagittal planes.

CONCLUSION

The cephalometric analyses of facial asymmetry were significantly inconsistent depending on the reference determination of midsagittal plane. The reference for midsagittal plane should be carefully determined in three-dimensional cephalometric analysis of facial asymmetry of patients with class III dentofacial deformity.

Mandibular third molar space in different antero-posterior skeletal patterns

Retromolar space has long been identified as a major factor in the aetiology of mandibular third molar impaction. The aims of this study were to compare mandibular third molar space between the different antero-posterior (A-P) skeletal patterns, between erupted and impacted third molars in the different A-P skeletal patterns, and to report on the status of third molar eruption/impaction among the studied subjects. A total of 432 mandibular third molars in 270 subjects (132 females and 138 males) were investigated from dental pantomograms (DPTs) and lateral cephalograms (LC). The average age for the total sample was 20.80 ± 2.03 years. The subjects were divided into three groups according to their ANB angle as follows: skeletal Class I (144 third molars in 90 subjects), skeletal Class II (145 third molars in 95 subjects), and skeletal Class III (143 third molars in 85 subjects). Each group was subdivided into impacted and erupted subgroups. DPT and LC were traced and the following variables were measured: retromolar space width, third molar width and angulation, β angle, second molar angulation, mandibular length, and gonial angle. Independent t-test, analysis of variance, and chi-square test were used for statistical analysis. Retromolar space width in the Class III subjects was smaller than in the Class I subjects (P < 0.05). Mandibular third molars were recorded as impacted in 26, 32, and 42 per cent of the Class I, II, and III subjects, respectively (P < 0.001). The impacted groups had a reduced retromolar space width, increased β angle, and reduced third molar angulation in all A-P skeletal patterns. Class III subjects showed increased mandibular third molar impaction with reduced retromolar space width.

Skeletal and dental asymmetries in Class II subdivision malocclusions using cone-beam computed tomography

INTRODUCTION

The objective of this study was to compare the degrees of skeletal and dental asymmetry between subjects with Class II subdivision malocclusions and subjects with normal occlusions by using cone-beam computed tomography.

METHODS

Thirty subjects with Angle Class II subdivision malocclusions (mean age, 13.99 years) and 30 subjects with normal occlusions (mean age, 14.32 years) were assessed with 3-dimensional cone-beam computed tomography scans. Independent t tests were used to compare orthogonal, linear, and angular measurements between sides and between groups.

RESULTS

Total mandibular length and ramus height were shorter on the Class II side. Pogonion, menton, and the mandibular dental midline were deviated toward the Class II side. Gonion and the anterior condyle landmark were positioned more posteriorly on the Class II side. The mandibular dental landmarks were located more latero-postero-superiorly, and the maxillary dental landmarks more latero-antero-superiorly on the Class II side. There was loss of maxillary arch length, and the mandibular molar was closer to the ramus on the Class II side.

CONCLUSIONS

The etiology of Class II subdivision malocclusions is primarily due to an asymmetric mandible that is shorter and positioned posteriorly on the Class II side. A mesially positioned maxillary molar and a distally positioned mandibular molar on the Class II side are also minor contributing factors.

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.

Orthodontic treatment alternative to a class III subdivision malocclusion

Class III malocclusions are considered one of the most complex and difficult orthodontic problems to diagnose and treat. Skeletal and/or dental asymmetries in patients presenting with Class III malocclusions can worsen the prognosis. Recognizing the dentoalveolar and skeletal characteristics of subdivision malocclusions and their treatment possibilities is essential for a favorable nonsurgical correction. Therefore, this article presents a nonsurgical asymmetric extraction approach to Class III subdivision malocclusion treatment which can significantly improve the occlusal and facial discrepancies.

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.

Third molar availability in Class II subdivision malocclusion

INTRODUCTION

In this study, we compared retromolar available space and third molar angulation between the Class I and Class II sides in patients with Class II subdivision malocclusion.

METHODS

Two samples were obtained from 46 subjects grouped according to the following characteristics: group 1 comprised 29 subjects (17 male, 12 female) with Class II subdivision malocclusion at a mean age of 14.73 years. Group 2 was the control to assist in the asymmetry evaluation and included 17 subjects (11 female, 6 male) with normal occlusion at a mean age of 21.73 years. Corrected oblique radiographs of each patient side were obtained to evaluate right and left retromolar available space and third molar angulation. The retromolar space and third molar angulations in the Class I and Class II sides in each group were compared with paired t and Wilcoxon tests. Asymmetry between the Class I and Class II sides of the Class II subdivision malocclusion group was compared with asymmetry between the right and left sides of the normal occlusion group with independent t and Mann-Whitney tests.

RESULTS

The results demonstrated significant differences between the Class I and Class II retromolar available spaces in the Class II subdivision malocclusion group. Significant angular asymmetry between these sides was observed only for the mandibular third molars. However, when retromolar space asymmetry and third molar angular asymmetry were compared between the Class II subdivision malocclusion and the normal occlusion groups, there were significant differences only for retromolar space asymmetry.

CONCLUSIONS

Patients with Class II subdivision malocclusion have asymmetric amounts of maxillary and mandibular retromolar available space and asymmetric angulation of the mandibular third molars between the Class I and Class II sides.