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

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.

Evaluation of occlusal force in Class II subdivision malocclusion

BACKGROUND

Class II subdivision is a malocclusion characterized by dental and functional asymmetry that is difficult to manage. Impaired muscle function can result in asymmetrical growth, leading to occlusal instability.

OBJECTIVE(S)

The study aimed to assess occlusal force in patients with Class II subdivision malocclusion using Innobyte. Additionally, the discrepancies of force generated at the position of maximum intercuspidation between the left and right sides of the arches were evaluated.

METHODS

The occlusal force of 66 patients with Class II subdivision malocclusion (group S) was measured and compared with that of 66 patients with Class I (group I) and 66 patients with Class II malocclusion (group II). The S group patients had a Class I molar on the right side and a Class II molar on the left side. ANOVA test, followed by the Games-Howell post hoc test, was performed to compare the mean of the total force among the groups. To assess the difference in force between the right and left arches, one-way ANOVA test followed by Tukey's post hoc comparison was performed. Finally, a boxplot was created to show the trend of occlusal force recorded in the three groups of patients.

RESULTS

The occlusal force differed significantly among the groups (p < .001). Post hoc Games-Howell analysis showed significant differences as follows: the total force in group S was 165.24 N greater than in group II and in group I was 218.06 N greater than in group II. The difference (right-left) in total force between the groups was statistically significant (p < .001). Tukey's post hoc test showed following significant correlation: in group S was 53.51 N greater than in group II and 63.12 N greater than in group I.

CONCLUSIONS

Among the analysed groups, patients with Class II malocclusion exhibited the lowest value of occlusal force. In patients with Class II subdivision malocclusion, force asymmetry, characterised by a higher value on the Class I side and a lower value on the Class II side was observed.

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.

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.

A 3D mirroring and colormap asymmetry study of Class II subdivision patients

INTRODUCTION

Patients with Class II subdivision malocclusion present skeletal and dental asymmetries. The purpose of this study is to assess those asymmetries by 3D mirroring and colormap quantification.

METHODS

This study analyzed 50 initial CBCTs divided into two groups: Class I (control group) and Class II subdivision (study group) malocclusion patients. CBCTs were oriented and full skull was segmented generating a 3D model. The right side of the 3D models was mirrored, using a midsagittal plane as reference, resulting in a perfectly symmetric skull based on two right sides. Original and mirrored models were superimposed on the unchanged right half, and differences were quantified using a colormap. Eight regions of interest were assessed: gonion, mandibular front, maxillary front, zygomatic process, maxillary and mandibular canine and molar areas.

RESULTS

Statistically significant differences using the Mann-Whitney test were found in six of the eight evaluated areas when comparing the control to the study group. The maxillary skeletal areas did not show any difference between the groups.

CONCLUSIONS

Patients with Class II subdivision malocclusion show true skeletal and dental asymmetries when comparing right and left sides. The maxilla showed no significant skeletal asymmetry, but the maxillary teeth were positioned more mesially on the Class II side. The maxillary canine on the Class II side was also more bucally positioned. The mandible showed significant asymmetries with both skeletal and dental areas in the Class II side more distally and bucally positioned.

Class II subdivision: Cone beam computed tomography- CBCT Analysis

Background

To estimate whether there is skeletal and/or dental asymmetry in class II subdivision patients, between the Class II side and the Class I side using of cone beam computed tomography (CBCT).

Material and Methods

A sample of 30 patients, from a private clinic, retrospectively selected; with a class II subdivision diagnosis requiring treatment, who underwent wide-field CBCT that met the inclusion criteria. The data was processed with Dolphin 3D version 11.95 Premium software. The craniometric points, as well as the spatial orientation scheme of the three-dimensional model were proposed by Craig Minich, et al. (1).

Results

The Class II subdivision side and the Class I side of each patient were compared through intramaxillary, intramandibular, and intermaxillary measurements, evaluating each one in three dimensions (sagittal, frontal, and axial). Also, the measurements made from the three-dimensional volume, were contrasted with those generated in the biplane views. The level of significance used was 0.05. Statistical analysis was performed using the R program (R Development Core Team), version 3.4.4. The intraoperative variability was previously verified using the Dahlberg formula. This error is 0.35 -1.10, so the spatial orientation and placement of craniometric points are repeatable and reliable.

Conclusions

Statistically significant differences have been found with respect to skeletal values and dentoalveolar position. Regarding the skeletal findings, the class II subdivision side is narrower and there is a shortening of the condylar branch. In the dentoalveolar position on this side, the upper molar and canine are in an advanced position, the lower molar is posterior and lower than the contralateral and the lower canine is in a delayed position. Furthermore, measurements made from a two-dimensional image cannot be extrapolated with those made directly from a three-dimensional volume. The problem is generated by a deviation in dental position as well as an underlying asymmetry.

Key words:Class II subdivision, cone beam computed tomography, skeletal asymmetry, dentoalveolar position.

Analysis of Three-Dimensional Morphological Differences in the Mandible between Skeletal Class I and Class II with CBCT Fixed-Point Measurement Method

This study was aimed at determining the three-dimensional differences in the mandible morphology between skeletal class I and II patients, at exploring the pathogenic mechanisms and morphological characteristics of skeletal class II, and at providing clinical references. The subjects were assigned to two groups according to the size of ANB angle: skeletal class I (2° < ANB angle < 5°) and skeletal class II (5° < ANB angle < 8°). After cone-beam computed tomography (CBCT) scanning, 31 landmarks and 25 measurement items were determined by In Vivo Dental 5.1 software (Anatomage, CA) for statistical analysis. The results were as follows: Co-Go, Go-Me, and CdM-CdD in skeletal class II cases were smaller than those in skeletal class I, and GoR-Me-GoL, GoR-Me-CoL, and, Ig-Men were larger than those in skeletal class I cases. In conclusion, there were significant differences in the three-dimensional morphology of the mandible between skeletal class I and class II patients. The vertical growth of the ramus, the horizontal growth of the mandibular body, and the condyle in skeletal class II patients were smaller than those in skeletal class I cases. In skeletal class II, the growth of the anterior part of the mandible in the vertical direction was larger than that in skeletal class I, and the shape of the mandible was more extended.

Analysis of facial skeletal asymmetry during foetal development using μCT imaging

OBJECTIVES

Asymmetry has been noted in the human craniofacial region in several pathological conditional and growth abnormalities, often with a directional predilection. Physiological asymmetry has also been reported in normal adults and adolescents, with certain regions of the cranioskeleton, such as the mandible, displaying prevalent asymmetry. However, the timing at which such asymmetries arise has not been evaluated. The objectives of this study were to assess the degree of asymmetry in facial bones during the foetal stages of human development.

MATERIAL AND METHODS

Twenty-one preserved conceptuses from the Congenital Anomaly Research Center at Kyoto University, between ages 15 and 20 weeks of gestation, were studied using high-resolution μCT imaging. Asymmetry analysis was performed on digitally segmented facial bone pairs, using geometric morphometric (GM) approaches as well as adapted deformation-based asymmetry (DBA) methods.

RESULTS

GM analysis revealed that the developing facial bones display statistically significant fluctuating and directional asymmetry. DBA methods suggest that the magnitude of asymmetry in facial bones is low and does not appear to be correlated to the estimate of overall size of conceptus. Additionally, the patterns of asymmetry are highly variable between individual specimens.

CONCLUSIONS

The developing foetal facial skeleton displays variable patterns of low magnitude asymmetry. GM and DBA methods offer unique advantages to assess facial asymmetry quantitatively and qualitatively.

Dentoalveolar changes in adults promoted by the use of auxiliary expansion arch: A cbct study

Background

The objective of this study was to evaluate the dentoalveolar effects and the changes of buccal cortical bone in the posterior area after expansion obtained with TMA auxiliary expansion arch in adult patients.

Material and Methods

A retrospective analysis of CT scans of 13 patients (6 male, 7 female) treated at a private clinic, taken immediately before and after the use of an auxiliary expansion archwire, was performed. Mean age at installation of TMA auxiliary expansion arch was 29.23 years (s.d.=9.13) and the mean age when the auxiliary arch was removed was 29.52 years (s.d.=9.16). Mean time of the use of the TMA auxiliary expansion arch was 0.29 years (s.d.=0.09). The patients used fixed appliances and after leveling and alignment, a TMA auxiliary expansion arch was installed, combined with the primary 0.017x0.025-inch thermoactivated Ni-Ti archwire. CBCT scans were taken at T1 and T2. Linear and angular measurements regarding the positioning of maxillary molar, premolars and canines were performed. Intragroup comparison of the variables at T1 and T2 was performed with dependent t tests.

Results

There was statistically significant transverse increase and buccal inclination of all teeth. The cortical bone showed adaptability and displacement in the same direction of tooth movement, but in smaller amounts.

Conclusions

The auxiliary expansion arch proved to be effective to correct dentoalveolar constriction in adult patients, by increasing the buccal dental inclination with larger displacements than the bone crest adaptation and with significant transverse gains.

Key words:Cone-Beam Computed Tomography, Maxillary Expansion, Adult treatment.

[Research progress on the relationship between centric relation and orthodontic treatment]

Centric relation (CR) is one of the core research contents in orthodontics, prosthodontics, and gnathology, acting as an important physiological factor in reconstructing the occlusion and adjusting the occlusal relationship. For over a century, CR is still a controversial subject in dentistry. CR has been redefined for several times, and recently, its application has been widened in orthodontics, including orthodontic diagnosis, clinical examination and analysis, and treatment goals. The purpose of this article is to review the definition of CR, its relationship with malocclusion, and the application of this relationship in orthodontic treatment.

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.

Biomechanics of Extra-alveolar Mini-Implant Use in the Infrazygomatic Crest Area for Asymmetrical Correction of Class II Subdivision Malocclusion

Asymmetric malocclusion has always represented a challenge to orthodontists, with different dental, skeletal, or dentoskeletal factors being probable causes for the condition. It is a key to distinguish between dental and skeletal asymmetry before determining a predictable force system for corrective treatment. The use of mini-implants (MIs) to address anchorage needs in modern orthodontic practice has become an important tool for orthodontists. They have been widely used for anchorage reinforcement purposes and placed in the dentoalveolar region, especially between tooth roots. However, placement sites other than root areas allow more versatility of orthodontic movement since tooth roots do not interfere in tooth displacement. The objective of the present study is to present a clinical case of asymmetric malocclusion (Class II division 1 subdivision), in which a MI placed in the infrazygomatic crest area was used for correction of the maxillary asymmetry by means of unilateral distalization. Biomechanics of unilateral molar distalization combined with skeletal anchorage has allowed predictable outcomes to be achieved with minimal need for patient’s compliance and minor side effects.

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.

Three-dimensional positional assessment of glenoid fossae and mandibular condyles in patients with Class II subdivision malocclusion

OBJECTIVES

To test the null hypotheses that the positions of the glenoid fossae and mandibular condyles are identical on the Class I and Class II sides of patients with Class II subdivision malocclusion.

MATERIALS AND METHODS

Retrospective three-dimensional (3D) assessments of the positions of the glenoid fossae and mandibular condyles were made in patients with Class II malocclusion. Relative to a fiducial reference at the anterior cranial base, distances from the glenoid fossae and condyles were calculated in pretreatment cone beam computed tomographic scans of 82 patients: 41 with Class II and 41 with Class II subdivision malocclusions. The 3D distances from glenoid fossae to sella turcica in the X (right-left), Y (anterior-posterior), Z (inferior-superior) projections were calculated.

RESULTS

Patients with Class II malocclusion displayed a symmetric position of the glenoid fossae and condyles with no statistically significant differences between sides (P > .05), whereas patients with Class II subdivision showed asymmetry in the distance between the glenoid fossae and anterior cranial base or sella turcica (P < .05), with distally and laterally positioned glenoid fossae on the Class II side. (P < .05). Male patients had greater distances between glenoid fossae and anterior cranial fossae (P < .05). The condylar position relative to the glenoid fossae did not differ between the two malocclusion groups nor between males and females (P > .05).

CONCLUSIONS

The null hypotheses were rejected. Patients with Class II subdivision malocclusion displayed asymmetrically positioned right- and left-side glenoid fossae, with a distally and laterally positioned Class II side, although the condyles were symmetrically positioned within the glenoid fossae.

Effects of surgically assisted rapid maxillary expansion on mandibular position: a three-dimensional study

Background

This study aimed to evaluate three-dimensional changes in mandibular position after surgically assisted rapid maxillary expansion (SARME).

Methods

A retrospective study was carried out with tomographic records of 30 adult patients with maxillary transverse deficiency who underwent SARME. Cone beam computed tomography scans were obtained preoperatively (T1), after expansion (T2) and 6 months after expansion (T3). Mandibular landmarks were measured with respect to axial, sagittal, and coronal planes. Repeated measures ANOVA was used for statistical analysis.

Results

Clockwise rotation and lateral displacement of the mandible were observed immediately after SARME. However, mandibular displacements tended to return close to their initial values at T3.

Conclusions

Clockwise rotation and lateral shift of the mandible are transient effects of SARME.

Craniofacial features affecting mandibular asymmetries in skeletal Class II patients

OBJECTIVES

The aim of this study was to evaluate the characteristics affecting different intensities of mandibular asymmetry in skeletal Class II adults using three-dimensional images. This study is clinically relevant since it allows professionals to evaluate the morphological components related to these deformities and more carefully obtain correct diagnosis and treatment plan for such patients.

METHODS

Cone-beam computed tomography data of 120 Class II patients (40 with relative symmetry, 40 with moderate asymmetry, and 40 with severe asymmetry) were imported to SimPlant Ortho Pro^® 2.0 software (Dental Materialise, Leuven, Belgium). Three reference planes were established and linear measurements were performed from specific landmarks to these planes, comparing the deviated side and the contralateral side in each group, as well as the differences between groups. The correlation between midline mandibular asymmetry and other variables was also evaluated. Statistical analyses considered a significance level of 5%.

RESULTS

Comparing the values obtained on the deviated side and on the contralateral side, there were significant differences for patients with moderate asymmetry and severe asymmetry. However, differences were seen more often in severe mandibular asymmetries. In those patients, there was a significant correlation of the gnathion deviation with lower dental midline deviation, difference in the lateral gonion positions, difference in the mandibular rami heights, and difference in the jugale vertical displacements.

CONCLUSIONS

For skeletal Class II patients with mandibular asymmetry, some craniofacial features are related to chin deviation and require proper evaluation, including the bilateral differences in the ramus height, mandibular body length, transverse and vertical positioning of the gonion and jugale points.

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.

Unilateral Maxillary First Molar Extraction in Class II Subdivision: An Unconventional Treatment Alternative

The asymmetrical intra-arch relationship in Class II subdivision malocclusion poses challenges in the treatment planning and mechanotherapy of such cases. This case report demonstrates a treatment technique engaging unilateral extraction of a maxillary first molar and Begg fixed appliances. The outcome stability and the enhancing effect on the eruption of the third molar in the extraction segment were confirmed by a 4-year follow-up examination.

Alveolar bone changes after asymmetric rapid maxillary expansion

OBJECTIVE

To quantitatively evaluate the effects of asymmetric rapid maxillary expansion (ARME) on cortical bone thickness and buccal alveolar bone height (BABH), and to determine the formation of dehiscence and fenestration in the alveolar bone surrounding the posterior teeth, using cone-beam computed tomography (CBCT).

MATERIALS AND METHODS

The CBCT records of 23 patients with true unilateral posterior skeletal crossbite (10 boys, 14.06 ± 1.08 years old, and 13 girls, 13.64 ± 1.32 years old) who had undergone ARME were selected from our clinic archives. The bonded acrylic ARME appliance, including an occlusal stopper, was used on all patients. CBCT records had been taken before ARME (T1) and after the 3-month retention period (T2). Axial slices of the CBCT images at 3 vertical levels were used to evaluate the buccal and palatal aspects of the canines, first and second premolars, and first molars. Paired samples and independent sample t-tests were used for statistical comparison.

RESULTS

The results suggest that buccal cortical bone thickness of the affected side was significantly more affected by the expansion than was the unaffected side (P < .05). ARME significantly reduced the BABH of the canines (P < .01) and the first and second premolars (P < .05) on the affected side. ARME also increased the incidence of dehiscence and fenestration on the affected side.

CONCLUSIONS

ARME may quantitatively decrease buccal cortical bone thickness and height on the affected side.

Reliability of CBCT in the diagnosis of dental asymmetry

Objective

The aim of this study was to validate a method used to assess dental asymmetry, in relation to the skeletal midline, by means of CBCT.

Methods

Ten patients who had CBCT scans taken were randomly selected for this study. Five different observers repeated 10 landmarks (x, y and z variables for each) and 12 linear measurements within 10 days. Measurements were taken in both arches to evaluate symmetry of first molars, canines and dental midline in relation to the skeletal midline. Intraclass correlation coefficient (ICC) was carried out to assess intra- and interobserver reliability for landmarks and distances. Average mean difference was also assessed to check measurement errors between observers.

Results

ICC landmarks was ≥ 0.9 for 27 (90%) and 25 (83%) variables for intra- and interobserver, respectively. ICC for distances was ≥ 0.9 for 7 (58%) and 5 (42%), respectively. All ICC landmarks for distances were >0.75 for both intra- and interobserver. The mean difference between observers was ≤ 0.6 mm for all the distances.

Conclusion

The method used to assess dental asymmetry by means of CBCT is valid. Measurements of molars, canines and dental midline symmetry with the skeletal midline are reproducible and reliable when taken by means of CBCT and by different operators.

The use of three-dimensional cephalometric references in dentoskeletal symmetry diagnosis

OBJECTIVE:

The aim of this study is to assess dentoskeletal symmetry in cone-beam computed tomography (CBCT) scans of Brazilian individuals with Angle Class I malocclusion.

MATERIAL:

A total of 47 patients (22 females and 25 males) aged between 11 and 16 years old (14 years) seen in a private radiology service (CIRO, Goiânia, GO, Brazil) were assessed. All CBCT scans were obtained from January, 2009 to December, 2010. Cephalometric measurements were taken by multiplanar reconstruction (axial, coronal and sagittal) using Vista Dent3DPro 2.0 (Dentsply GAC, New York, USA). Minimum, maximum, mean and standard deviation values were arranged in tables, and Student t-test was used to determine statistical significance (P < 0.05).

RESULTS:

Data were homogeneous, and differences between the right and left sides were not significant.

CONCLUSIONS:

Cephalometric measurements of Brazilian individuals with Angle Class I malocclusion can be used to establish facial symmetry and three-dimensional standard references which might be useful for orthodontic and surgical planning.

Effects of early unilateral mandibular first molar extraction on condylar and ramal vertical asymmetry

Objective:

The objective of the following study is to investigate the mandibular vertical asymmetry in a group of patients with early unilateral mandibular first molar extractions.

Materials and Methods:

Mandibular asymmetry index measurements (condylar, ramal and condylar-plus-ramal) were performed on the panoramic radiographs of a study group including 51 patients (mean age: 18.60 ± 1.11 years) and a control group of 51 patients (mean age: 18.53 ± 1.29 years). Group I included patients with a unilateral mandibular first molar extracted before the age of 12 years. Group II included patients with no extractions and had excellent Class I relationships, no missing teeth and slight or moderate anterior crowding. A paired t-test was used to determine possible statistically significant differences between the sides for the measurements. Student's t-test was used for the comparison of asymmetry index values between the groups and genders.

Results:

No group showed statistically significant sex-or side-specific differences for posterior vertical height measurements. Condylar asymmetry index and ramal asymmetry index measurements were not statistically different between the groups, while condylar-plus-ramal asymmetry index (CRAI) measurements were statistically different between the groups (P = 0.019).

Conclusions:

A slight difference for CRAI value was found in patients with early unilateral mandibular first molar extractions.

Quantification of skeletal asymmetries in normal adolescents: cone-beam computed tomography analysis

BACKGROUND

The detection and quantification of skeletal asymmetries is a fundamental component to diagnosis and treatment planning in orthodontics. The purpose of this study was to identify and quantify the characteristics of facial and dental asymmetries in a normal, adolescent population using 3D imaging.

METHODS

Thirty consecutive Class I patients (mean age 14.32 years, SD 1.67) meeting the inclusion criteria were analyzed by three-dimensional cone-beam computed tomography (CBCT). Dental, maxillary, mandibular, and cranial base variables were measured with Dolphin 3D. CBCT analysis consisted of the localization of 34 anatomical landmarks. All reference points were digitized in 3D and analyzed using 67 skeletal and dental measurements. Student's t tests for paired samples were used with a significance level of p < 0.05.

RESULTS

Minor right-left discrepancies were noted in all planes. The most anterior point of the glenoid fossa and most condylar points were positioned more superior and lateral on the right side, compared to the left side. Porion was also located more superiorly on the right side relative to the left side. The posterior nasal spine was found to be located to the right of the midsagittal plane. Slight dental midline discrepancies were found, and the dental arch lengths were slightly longer on the left side compared to the right. The height of the ramus, in both 3D and 2D, and the inclination of the ramus were greater on the right than that on the left side.

CONCLUSIONS

The findings of this study suggest minor asymmetries exist and are likely a common occurrence in the normal human craniofacial complex. Additionally, a natural compensatory mechanism may exist which controls the size and shape of specific tissues in order to maintain functional symmetry.

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.

Evaluation of alveolar bone loss following rapid maxillary expansion using cone-beam computed tomography

Objective

To evaluate the changes in cortical bone thickness, alveolar bone height, and the incidence of dehiscence and fenestration in the surrounding alveolar bone of posterior teeth after rapid maxillary expansion (RME) treatment using cone-beam computed tomography (CBCT).

Methods

The CBCT records of 20 subjects (9 boys, mean age: 13.97 ± 1.17 years; 11 girls, mean age: 13.53 ± 2.12 year) that underwent RME were selected from the archives. CBCT scans had been taken before (T1) and after (T2) the RME. Moreover, 10 of the subjects had 6-month retention (T3) records. We used the CBCT data to evaluate the buccal and palatal aspects of the canines, first and second premolars, and the first molars at 3 vertical levels. The cortical bone thickness and alveolar bone height at T1 and T2 were evaluated with the paired-samples t-test or the Wilcoxon signed-rank test. Repeated measure ANOVA or the Friedman test was used to evaluate the statistical significance at T1, T2, and T3. Statistical significance was set at p < 0.05.

Results

The buccal cortical bone thickness decreased gradually from baseline to the end of the retention period. After expansion, the buccal alveolar bone height was reduced significantly; however, this change was not statistically significant after the 6-month retention period. During the course of the treatment, the incidence of dehiscence and fenestration increased and decreased, respectively.

Conclusions

RME may have detrimental effects on the supporting alveolar bone, since the thickness and height of the buccal alveolar bone decreased during the retention period.

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).

Effects of early bilateral mandibular first molar extraction on condylar and ramal vertical asymmetry

OBJECTIVES

This study aims to investigate the mandibular vertical asymmetry in a group of adult patients who had early bilateral mandibular first molar extractions.

METHODS

Mandibular asymmetry index measurements (condylar, ramal, and condylar plus ramal) were made on the panoramic radiographs of a study group including 30 subjects (mean age, 18.22 ± 1.30 years) and a control group of 25 subjects (mean age, 18.24 ± 1.17 years). Group I comprised the control group patients with no extractions and had excellent class I relationships, no missing teeth, and slight or moderate anterior crowding. Group II included patients with a bilateral mandibular first molar teeth extracted before the age of 12 years. Student's t test was used for the comparison of asymmetry index values between the groups. A paired t test was used to determine possible statistically significant differences between the sides for condylar, ramal, and condylar plus ramal height measurements.

RESULTS

No group showed statistically significant side-specific differences for posterior vertical height measurements. Condylar asymmetry index (CAI), ramal asymmetry index, and condylar plus ramal asymmetry index measurements were not statistically different between the groups (p > 0.05).

CONCLUSIONS

CAI values were significantly high when compared with the 3 % threshold value in the both groups, but comparisons between the groups were not statistically significant.

CLINICAL RELEVANCE

This article investigates the effects of early bilateral mandibular molar teeth extraction that has never been investigated in the literature. The present study showed that the lengths of the condylar, ramal, and condylar plus ramal height were less in the study group than in a well-matched control group of without extraction.

Mandibular lateral shift induces the increased expression of TGF-β, VEGF, and Col-II in the condyle of rat temporomandibular joints

OBJECTIVE

The present study evaluates histologic changes to and expression of angiogenic factors in rats with mandibular functional shift (MFS).

STUDY DESIGN

After 1, 2, and 4 weeks of MFS, rats in the experimental and control groups were killed. Histologic micrographs of the ipsilateral condyle cartilage were obtained. The localization and expression of vascular endothelial growth factor (VEGF), transforming growth factor beta (TGF-β), and type-II collagen (Col-II) in temporomandibular joints (TMJs) were evaluated through immunohistochemical staining.

RESULTS

The results showed that structural changes in the condyle cartilage could be observed 2 weeks after MFS. TGF-β expression reached its peak 2 weeks post-MFS, whereas VEGF and Col-II reached their peaks 4 weeks posttreatment.

CONCLUSIONS

Compressive forces applied to the TMJ could enhance the expressions of VEGF, TGF-β, and Col-II, and activate angiogenesis. The proteins appear to play important roles in the remodeling of the TMJ.