Mandibular Deviation and Unilateral Posterior Crossbite Treated with Intraoral Vertical Ramus Osteotomy and Sagittal Split Ramus Osteotomy

Adult patients with severe mandibular asymmetry are often treated with a combination of surgery and orthodontic treatment to improve facial esthetics and occlusion. Intraoral vertical ramus osteotomy is a useful surgical procedure for mandibular setback in patients with mandibular prognathism or mandibular asymmetry. A 17-year-old woman presented with a Class III malocclusion with facial asymmetry and a unilateral posterior crossbite. The patient was treated orthodontically with edgewise appliances and surgically with intraoral vertical ramus osteotomy and sagittal split ramus osteotomy. The combined surgical-orthodontic treatment resulted in facial symmetry and optimal occlusion

A Unique Case of Primary Failure of Tooth Eruption with Mandibular Deformity

Primary failure of tooth eruption, which is extremely rare, has serious consequences and several possible causative factors. Teeth in the posterior quadrants of the upper and lower jaw are preferentially affected and when it occurs it usually results in an open bite extending from anterior to posterior. We report the case of a 29-year-old female patient who presented with primary failure of tooth eruption and mandibular deformity. The patient, who had no family history of tooth eruption failure, presented with impactions of the mandibular left molars. We discuss the clinical and radiographic features of this patient and describe the limitations of treatment for patients with eruption failure

Long-term Follow-up of a Temporomandibular Joint Cyst

We report a case of cystic lesion in a 23-year-old female, consisting of an oval-shaped lesion adjacent to the temporomandibular joint (TMJ). She presented with a Class III malocclusion with facial asymmetry and tenderness to palpation on the right TMJ. The patient was treated conservatively with a splint for the TMJ-associated cyst and combined surgical-orthodontic treatment for the facial asymmetry. The post-treatment course was uneventful. The authors recommend a conservative approach as one of the treatment options for TMJ cyst

Relationship between the position of the maxillary molars and the infrazygomatic crest morphology

This study aimed to evaluate the morphological characteristics of the infrazygomatic crest with various jaw morphologies, occlusal forces, and maxillary first molar position in three dimensions to explore various factors that affect the morphology of the infrazygomatic crest, and to obtain knowledge regarding the ideal maxillary first molar position. Seventy-three Japanese subjects （32males with a mean age of 22.50±6.23 years and 41 females with a mean age of 25.17±6.78 years） had their occlusal force measured and underwent cone-beam CT for orthodontic treatment. The subjects were categorized into the following three groups based on the mandibular plane angle （Mp）: hypodivergent group （Mp＜23°）, normodivergent group （Mp 23°‒30°）, and hyperdivergent group （Mp≥30°）. Subjects were also divided into two groups based on the maxillary first molar positions: mesial and distal. The thickness of the infrazygomatic crest was evaluated using cross-sectional cone-beam CT images obtained in the coronal and axial planes. The thickness of the infrazygomatic crest in the coronal plane significantly differed among the hypodivergent, normodivergent, and hyperdivergent groups and between the mesial and distal groups. The thickness of the infrazygomatic crest in the axial plane significantly differed among the hypodivergent, normodivergent, and hyperdivergent groups. In conclusion, differences in the maxillary first molar position and the vertical skeletal pattern may affect the morphology of the infrazygomatic crest

Eye-tracking system-based evaluation of orthodontists’ and patients’ visual attention to facial features before and after orthognathic surgery treatment

This research aims to determine the differences between the patient and orthodontist in terms of their visual attention using an eye-tracking system-based evaluation system for assessing facial features before and post orthognathic surgery. The participants included patients who underwent orthognathic treatment （n＝26; mean age, 26.04±6.6 years） at the Showa University Dental Hospital and orthodontists with ≥5 years of experience at our department （n＝10, mean age, 31.4±2.2 years）. Visual attention was assessed using an eyeglass-type device （eye tracker）. Facial photographs of each patient, both frontal and side views, were shown on a monitor to the patients and orthodontists, and their respective visual attention was comparatively assessed. SPSS Statistics 25 was used for the study data statistical analysis. The results were contrasted between the patients and the orthodontists using a linear mixed model, with photographs labeled with the same number serving as repeat factors. Total fixation analysis demonstrated that patients focused more on the lower face postoperatively （P＝0.044）, while orthodontists focused more on the entire face both postoperative and preoperatively. The postoperative findings also demonstrated significant differences in many areas. There was a significant difference in how orthodontists and patients examined the face. This study found differences in visual attention between patients and orthodontists when they examined facial features before and after orthognathic surgery

Experimental Verification of Finite Element Analysis for a Thermoplastic Orthodontic Aligner

In recent years, good outcomes have been reported using transparent and removable orthodontic appliances known as aligners. However, unpredicted tooth movement that contradicted 3-dimensional image simulations was observed in some cases. These anomalies could relate to biomechanical factors ; in particular, the characteristics of mechanical loading applied to the periodontal ligament and the tooth crown by aligners remain unclear. This study examines the biomechanical characteristics of aligners by a new method as follows : 1) development of an experimental model using artificial teeth and plastic aligners ; 2) finite element (FE) modeling and analysis using computed tomography (CT) images of the experimental model ; and, 3) comparison among observations of this actual model and standard FE analysis results. Roots of two artificial teeth were covered by silicone material at 1.0 mm intervals for each coronal proximal surface and plastic clear aligners were manufactured based on another model in which the interval was reduced to 0.0 mm to simulate bodily movement. An FE analysis model of this 1.0 mm teeth interval was reconstructed from the CT images. A virtual aligner based on the FE model was also generated with a 0.0 mm interval. Changes in space between the root surface and silicone in both the actual and FE model were compared with the aligner fitted in the initial model. Identical tendencies of movement were observed in both experimental results - the artificial teeth and computational results of FE analysis. Our method using an experimental and computational approach proved useful to examine aligner characteristics ; the use of such a biomechanical approach could further our understanding of aligner treatments