Maxillary molar intrusion and transverse decompensation to enable mandibular single-jaw surgery with rotational setback and transverse shift for a patient with mandibular prognathism and asymmetry

Classification and characterization of facial asymmetry in adult patients with skeletal Class III malocclusion using cluster analysis

INTRODUCTION

This study aimed to analyze the comprehensive maxillofacial features of patients with skeletal Class III malocclusion and facial asymmetry to develop a classification system for diagnosis and surgical planning.

METHODS

A total of 161 adult patients were included, with 121 patients in the asymmetry group (menton deviation >2 mm) and 40 patients in the symmetry group (menton deviation ≤2 mm). Twenty-eight variables were determined, including transverse translation, roll and yaw of each facial unit, transverse width, mandibular morphology, and transverse dental compensation. Principal component (PC) analysis was conducted to extract PCs, and cluster analysis was performed using these components to classify the asymmetry group. A decision tree was constructed on the basis of the clustering results.

RESULTS

Six PCs were extracted, explaining 80.622% of the data variability. The asymmetry group was classified into 4 subgroups: (1) atypical type (15.7%) showed an opposite roll direction of maxillary dentition than of menton deviation; (2) compound type (34.71%) demonstrated significant ramus height differences, maxillary roll, and mandibular roll and yaw; (3) mandibular yaw type (44.63%) showed slight mandibular yaw without mandibular morphology asymmetry; and (4) maxillary-shift type (4.96%) shared similarities with the compound type but showed significant maxillary translation. The classification and regression tree model achieved a prediction accuracy of up to 85.11%.

CONCLUSIONS

This study identified 4 distinct phenotypes using cluster analysis and proposed tailored treatment recommendations on the basis of their specific characteristics. The classification results emphasized the importance of spatial displacement features, especially mandibular yaw, in diagnosing facial asymmetry. The established classification and regression tree model enables clinicians to identify patients conveniently.

Changes in masseter muscle morphology after surgical-orthodontic treatment in patients with skeletal Class III malocclusion with mandibular asymmetry: The automatic masseter muscle segmentation model

INTRODUCTION

This study evaluated the masseter muscle changes after surgical-orthodontic treatment in patients with a skeletal Class III malocclusion using automatic segmentation.

METHODS

Images of 120 patients with skeletal Class III malocclusion were obtained and reconstructed at T0 (pretreatment), T1 (presurgery), and T2 (6-12-month postsurgery). The patients were divided into symmetrical and asymmetrical groups. The volume, major axis length, maximum cross-sectional area, horizontal cross-sectional area 5 mm above the mandibular foramen (CSAF), and orientation were calculated automatically.

RESULTS

In the asymmetrical group, the volume and major axis length on the deviated side were lower than on the nondeviated side at T0, T1, and T2 (P <0.05). There were no significant differences in maximum cross-sectional area and CSAF bilaterally. The orientation was coronally more vertical and sagittally more forward on the deviated side (both P <0.001). In the symmetrical group, there were no significant bilateral differences at T0, T1, and T2. The volume, major axis length, and CSAF decreased, and the coronal orientation was more vertical on the nondeviated side at T2 than at T0 in both groups (P <0.05). The coronal plane orientation was more inclined on the deviated side at T2 than at T0 in the asymmetrical group (P <0.05).

CONCLUSIONS

The smaller volume on the deviated side at T2 indicates the need for myofunctional training after surgery. The masseter muscle volume and the cross-sectional area did not recover to the preorthodontic levels. Studies with longer follow-up durations are needed to confirm these findings.

Facial deformity correction and genioplasty; a case report and literature review

Introduction

dentofacial deformities are mainly congenital problems that distort the face structure. However, they have many adverse effects on adolescents' quality of life and self-esteem.

Case presentation

We report a case of an 18-year-old female with no family history or previous surgical method. She presented to our hospital with a facial deformity, including a midline shift of 1.5 teeth to the left side and a malalignment of dentation. Orthopantomography (OPG) X-ray and cephalometric X-ray assessed the deformity extent and determined the appropriate surgical procedure. As a result, the patient underwent genioplasty and bimaxillary (BiMax) surgery to correct the problem.

Discussion

Facial deformities occur during the normal embryonic phase and develop clearly when the patient reaches puberty due to a growth spurt. Some researchers encourage early correction, while others recommend the surgery only after completing the growth. However, the perfect age for this surgery is 19 years old for boys and 17 for girls after the cessation of facial growth. Therefore, our patient underwent surgery at 18 years old, which is the desirable age.

Conclusion

Genioplasty and BiMax are reasonable procedures to treat facial deformities and correct malalignment of dentation in an 18-year-old patient without major complications.

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Dentofacial deformities are rare congenital problems that can be improved significantly with the right procedure.

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The combination of genioplasty and bimaxillary (BiMax) surgery is effective as a treatment for facial asymmetry class 1.

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The combination of genioplasty and bimaxillary (BiMax) surgery can achieve an uneventful recovery without major complications.

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Age 18 is a suitable age for the combination of genioplasty and bimaxillary (BiMax) surgery with favorable outcomes.

Comparison of one-jaw and two-jaw orthognathic surgery in patients with skeletal Class III malocclusion using data from 10 multi-centers in Korea: Part I. Demographic and skeletodental characteristics

Objective

To investigate demographic and skeletodental characteristics of one-jaw (1J-OGS) and two-jaw orthognathic surgery (2J-OGS) in patients with skeletal Class III malocclusion.

Methods

750 skeletal Class III patients who underwent OGS at 10 university hospitals in Korea between 2015 and 2019 were investigated; after dividing them into the 1J-OGS (n = 186) and 2J-OGS groups (n = 564), demographic and skeletodental characteristics were statistically analyzed.

Results

2J-OGS was more frequently performed than 1J-OGS (75.2 vs. 24.8%), despite regional differences (capital area vs. provinces, 86.6 vs. 30.7%, p < 0.001). Males outnumbered females, and their mean operation age was older in both groups. Regarding dental patterns, the most frequent maxillary arch length discrepancy (ALD) was crowding in the 1J-OGS group (52.7%, p < 0.001) and spacing in the 2J-OGS group (40.4%, p < 0.001). However, the distribution of skeletal pattern was not significantly different between the two groups (all p > 0.05). The most prevalent skeletal patterns in both groups were hyper-divergent pattern (50.0 and 54.4%, respectively) and left-side chin point deviation (both 49.5%). Maxillary spacing (odds ratio [OR], 3.645; p < 0.001) increased the probability of 2J-OGS, while maxillary crowding (OR, 0.672; p < 0.05) and normo-divergent pattern (OR, 0.615; p < 0.05) decreased the probability of 2J-OGS.

Conclusions

In both groups, males outnumbered females, and their mean operation age was older. The most frequent ALD was crowding in the 1J-OGS group, and spacing in the 2J-OGS group, while skeletal characteristics were not significantly different between the two groups.

Three-dimensional surgical management of a patient with Pruzansky I hemifacial microsomia and severe facial asymmetry: A 4-year follow-up

Treatment of hemifacial microsomia is challenging and often requires multiple interventions to restore function and facial esthetics. In this article, the combined orthodontic-surgical treatment of a young patient exhibiting Pruzansky I hemifacial microsomia is reported. The patient was aged 15 years, but his bone age was determined to be 18 years. His facial asymmetry was severe, with the nose and a retrusive chin deviated to the left side and a canted smile. The presurgical phase was aimed at centering the mandibular midline to the center of the chin through the distal movement of the mandibular left buccal dentition. The surgery was planned with 3-dimensional computer-aided surgical simulation and included a LeFort I and unilateral sagittal split osteotomies combined with a genioplasty. This report illustrates the therapeutic stages and a 4-year follow-up of a unique and complex orthognathic surgical approach, chosen among other alternatives and leading to improved function and appearance and stable results.

Root proximity of the anchoring miniscrews of orthodontic miniplates in the mandibular incisal area: Cone-beam computed tomographic analysis

Objective

This outcome analysis study evaluated the actual positions of the orthodontic miniplate and miniplate anchoring screws (MPASs) and the risk factors affecting adjacent anatomic structures after miniplate placement in the mandibular incisal area.

Methods

Cone-beam computed tomographic images of 97 orthodontic miniplates and their 194 MPASs (diameter, 1.5 mm; length, 4 mm) in patients whose miniplates provided sufficient clinical stability for orthodontic treatment were retrospectively reviewed. For evaluating the actual positions of the miniplates and analyzing the risk factors, including the effects on adjacent roots, MPAS placement height (PH), placement depth (PD), plate angle (PA), mental fossa angle (MA), and root proximity were assessed using the paired t-test, analysis of variance, and generalized linear model and regression analyses.

Results

The mean PDs of MPASs at positions 1 (P1) and 2 (P2) were 2.01 mm and 2.23 mm, respectively. PA was significantly higher in the Class III malocclusion group than in the other groups. PH was positively correlated with MA and PD at P1. Of the 97 MPASs at P1, 49 were in the no-root area and 48 in the dentulous area; moreover, 19 showed a degree of root contact (19.6%) without root perforation. All MPASs at P2 were in the no-root area.

Conclusions

Positioning the miniplate head approximately 1 mm lower than the mucogingival junction is highly likely to provide sufficient PH for the P1-MPASs to be placed in the no-root area.

A surgery-first approach using single-jaw rotational mandibular setback in low-angle mandibular prognathism

For the treatment of low-angle mandibular prognathism, rotational mandibular setback surgery is usually performed with Le Fort I maxillary osteotomy to rotate the maxillomandibular complex simultaneously. However, this maxillary surgery can be replaced with the orthodontic intrusion of maxillary posterior teeth. Single-jaw rotational mandibular setback surgery can be done with a surgery-first approach by planning orthodontic rotation of the maxillary occlusal plane with the simulation of the postsurgical forward mandibular rotation. This case report describes this approach applied to a 19-year-old female patient with low-angle mandibular prognathism but without maxillary deficiency. A Class II open bite was formed by the rotational setback surgery. During postsurgical orthodontic treatment, the maxillary total arch was distalized with maxillary molar intrusion using palatal mini-implants and lever. This case report demonstrates that orthodontic rotation of the maxillary occlusal plane and simulation of mandibular rotation can replace maxillary surgery and enable single-jaw rotational mandibular setback surgery with a surgery-first approach.