• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.48 no.1
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• pp.63-67
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• 2022

Controversies exist regarding the need for prophylactic extraction of mandibular third molars in patients who plan to undergo orthognathic surgery. An 18-year-old male patient was diagnosed with mandibular prognathism and maxillary retrognathism with mild facial asymmetry. He had a severely damaged mandibular first molar and a horizontally impacted third molar. After extraction of the first molar, the second molar was protracted into the first molar space, and the third molar erupted into the posterior line of occlusion. The orthognathic surgery involved clockwise rotation of the maxillomandibular complex as well as angle shaving and chin border trimming. Patients who are missing or have damaged mandibular molars should be monitored for eruption of third molars to replace the missing posterior tooth regardless of the timing of orthognathic surgery.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.14 no.1_2
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• pp.135-142
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• 1992

This study was performed to define the anatomical position of the mandibular canal and the findings during the sagittal split ramus osteotomy of the mandible. The mandibles of 20 adult Korean were used. The dimension of mandibular canal from the mandibular foramen to the 1st molar was measured at 4 specific coronal-sectional location by CT scan. The results were as follows ; 1. The distance from the mandibular canal to the medial aspect of the buccal cortical plate was greatest($4.5{\pm}1.1mm$) at 2nd molar area and was not significantly greater than at any other section. 2. Buccal cortex was thickest($3.8{\pm}0.9mm$) at 2nd molar and thinnest ($2.5{\pm}0.3mm$) mandibular foramen um 3. The distance from the mandibular canal to the medial aspect of the lingual cortical plate was not significant at any sections. 4. The distance from the mandible canal to the inferior border of mandible was greatest at the mandibular foramen($20.7{\pm}3.9mm$). The canal was located more closely to the inferior border at 1st, 2nd molar area 5. The diameter of the mandibular canal was between $2.5{\pm}0.3mm$ and $2.8{\pm}0.6mm$. 6. The total mandibular thickness was greatest($21.1{\pm}2.6mm$) at 2nd molar area and narrowest($17.2{\pm}3.2mm$) at mandibular foramen area.

• The korean journal of orthodontics
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• v.48 no.6
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• pp.357-366
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• 2018

Objective: The purpose of this study was to analyze the transverse dental compensation in reference to the maxillary and mandibular basal bones using cone-beam computed tomography (CBCT) and evaluate the correlations between transverse dental compensation and skeletal asymmetry variables in patients with skeletal Class III malocclusion and facial asymmetry. Methods: Thirty patients with skeletal Class I (control group; 15 men, 15 women) and 30 patients with skeletal Class III with menton deviation (asymmetry group; 16 men, 14 women) were included. Skeletal and dental measurements were acquired from reconstructed CBCT images using OnDemand3D 1.0 software. All measurements were compared between groups and between the deviated and nondeviated sides of the asymmetry group. Correlation coefficients for the association between skeletal and dental measurements were calculated. Results: Differences in the ramus inclination (p < 0.001), maxillary canine and first molar inclinations (p < 0.001), and distances from the canine and first molar cusp tips to the midmaxillary or midmandibular planes (p < 0.01) between the right and left sides were significantly greater in the asymmetry group than in the control group. In the asymmetry group, the ramus inclination difference (p < 0.05) and mandibular canting (p < 0.05) were correlated with the amount of menton deviation. In addition, dental measurements were positively correlated with the amount of menton deviation (p < 0.05). Conclusions: Transverse dental compensation was correlated with the maxillary and mandibular asymmetry patterns. These results would be helpful in understanding the pattern of transverse dental compensation and planning surgical procedure for patients with skeletal Class III malocclusion and facial asymmetry.

• The korean journal of orthodontics
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• v.22 no.1
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• pp.229-239
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• 1992

This study was performed to define the adaptation patterns of each skeletal components to the flexures of cranial bases, using 91 males from the ages of 17 to 36 and 64 females from the ages of 16 to 34, without orthodontic or prosthetic treatment experiences and with pleasant profiles as subjects. The conclusions are as follow: 1. When considering the changes of flexure of cranial base (Ba-SE-FMN) in both sexes, changes in the anterior cranial base angle to the PM Vertical line (SE-FMN/PMV) were greater than the changes in the posterior cranial base angle to the PM Vertical line (Ba-SE/PMV). Subsequently the nasomaxillary complex showed antero-superior rotating effect as the cranial base angles were increased and postero-inferior rotating effect as they were decreased. 2. Horizontal mandibular angle (Ba-SE-Me) was increased in both sexes as cranial base angle increases (Ba-SE-FMN) and it decreased as the latter was decreases. There by indicating compensatory effects. 3. Maxillary angle (SE-FMN-A) was decreased in both sexes as cranial base angle (Ba-SE-FMN) increases and it increased as the latter was decreased. There by indicating compensatory effects. 4. Mandibular ramus angle to posterior cranial base was decreased in both sexes as cranial base angle increases. There by indicating compensatory effect to anteriorly displaced maxilla and the mandibular ramus angle was increased as the cranial base angle decreases. There by indicating compensatory effect to posteriorly displace maxilla. 5. The length of posterior upper facial height was decreased in both sexes as the cranial base angle increases and it increased as the latter was decreased.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.40
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• pp.36.1-36.5
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• 2018

Background: Botulinum toxin-A (BTX-A) injection into muscle reduces muscular power and may prevent post-operative complication after orthognathic surgery. The purpose of this study was (1) to evaluate BTX-A injection into the masseter muscle on the prevention of plate fracture and (2) to compare post-operative relapse between the BTX-A injection group and the no injection group. Methods: Sixteen patients were included in this study. Eight patients received BTX-A injection bilaterally, and eight patients served as control. All patients received bilateral sagittal split ramus osteotomy for the mandibular setback and additional surgery, such as LeFort I osteotomy or genioplasty. Post-operative plate fracture was recorded. SNB angle, mandibular plane angle, and gonial angle were used for post-operative relapse. Results: Total number of fractured plates in patients was 2 out of 16 plates in the BTX-A injection group and that was 8 out of 16 plates in the no treatment group (P = 0.031). However, there were no significant differences in post-operative changes in SNB angle, mandibular plane angle, and gonial angle between groups (P > 0.05). Conclusions: BTX-A injection into the masseter muscle could reduce the incidence of plate fracture.

• The korean journal of orthodontics
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• v.52 no.2
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• pp.85-101
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• 2022

Objective: To classify facial asymmetry (FA) phenotypes in adult patients with skeletal Class III (C-III) malocclusion. Methods: A total of 120 C-III patients who underwent orthognathic surgery (OGS) and whose three-dimensional computed tomography images were taken one month prior to OGS were evaluated. Thirty hard tissue landmarks were identified. After measurement of 22 variables, including cant (°, mm), shift (mm), and yaw (°) of the maxilla, maxillary dentition (Max-dent), mandibular dentition, mandible, and mandibular border (Man-border) and differences in the frontal ramus angle (FRA, °) and ramus height (RH, mm), K-means cluster analysis was conducted using three variables (cant in the Max-dent [mm] and shift [mm] and yaw [°] in the Manborder). Statistical analyses were conducted to characterize the differences in the FA variables among the clusters. Results: The FA phenotypes were classified into five types: 1) non-asymmetry type (35.8%); 2) maxillary-cant type (14.2%; severe cant of the Max-dent, mild shift of the Man-border); 3) mandibular-shift and yaw type (16.7%; moderate shift and yaw of the Man-border, mild RH-difference); 4) complex type (9.2%; severe cant of the Max-dent, moderate cant, severe shift, and severe yaw of the Man-border, moderate differences in FRA and RH); and 5) maxillary reverse-cant type (24.2%; reverse-cant of the Max-dent). Strategic decompensation by pre-surgical orthodontic treatment and considerations for OGS planning were proposed according to the FA phenotypes. Conclusions: This FA phenotype classification may be an effective tool for differential diagnosis and surgical planning for Class III patients with FA.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.33 no.2
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• pp.190-197
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• 2011

The management of mandibular prognathism was revolutionized by the advent of the of sagittal split ramus osteotomy (SSRO) technique as described by Obwegesser and Trauner in 1957. Facial nerve palsy following SSRO is a rare but serious problem. In the event of post-operative facial palsy, careful clinical and neurophysiological investigations such as a nerve condunction test for facial function is mandatory. The authors examined patients with facial palsy following SSRO. Patients recovered after 3~4 months and we had performed clinical examinations with electromyography and nerve conduction tests during follow-up period.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.33 no.6
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• pp.505-511
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• 2011

Purpose: This study evaluated correlation and risk factors between position of the mandibular third molars and mandibular angle fractures using clinical and radiographic findings. Methods: Medical records and panoramic radiographs of 188 patients with mandibular fractures were retrospectively reviewed. The presence and position of the third molars were assessed for each patient and were related to the occurrence of mandibular angle fractures. Results: The incidence of mandibular angle fracture was found to be greater when a lower third molar was present, particularly at the occlusal plane positioned on the $2^{nd}$ molar occlusal surface (by Archer system) and the third molar is impacted in mandibular ramus (by Pell & Gregory system). Of the 192 sites with a lower third molar, 32 (16%) had an angle fracture. Of the 184 site without lower third molars, 16 (8%) had an angle fracture. Conclusion: This study confirmed an increased risk of angle fractures in the presence of a lower third molar as well as variable risk for angle fracture, depending on positioning of the third molar.

• Journal of The Korean Dental Society of Anesthesiology
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• v.9 no.1
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• pp.24-29
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• 2009

When performing the inferior alveolar nerve block anesthesia, surgeon often faced a difficulty of the surgical operation due to the incomplete anesthesia. One of the reason is the variety of mandibular canal anatomy. Up to now, there are some reports of index cases about bifid mandibular canal among mandibular canal anatomic variation, and some classification is applied according to anatomical location and configuration. When surgical operation is performed involving mandible such as dantal implant treatment, extraction of an impacted third molar, sagittal split ramus osteotomy, etc, the position of mandibular canal should be considered. Bifid mandibular canal clinically causes troublesome cases of anesthesia when inferior alvelor nerve block, especially is performed extraction of an impacted third molar. Therefore, It is important for clinicians to recognize the presence of bifid canals on radiographys. Nowadays, the position of mandibular canal can be measured precisely by using Dental CT. It is not found by panorama image but is found by Dental CT sometimes. Among the patients, which take panorama and Dental CT simultaneously, for tooth extraction of lower impacted third molar in our department, we report the case that did not identifying in panorama but identifying it in Dental CT.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.44 no.4
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• pp.167-173
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• 2018

Objectives: Classification of the degree of postoperative nerve damage according to contact with the mandibular canal and buccal cortical bone has been studied, but there is a lack of research on the difference in postoperative courses according to contact with buccal cortical bone. In this study, we divided patients into groups according to contact between the mandibular canal and the buccal cortical bone, and we compared the position of the mandibular canal in the second and first molar areas. Materials and Methods: Class III patients who visited the Dankook University Dental Hospital were included in this study. The following measurements were made at the second and first molar positions: (1) length between the outer margin of the mandibular canal and the buccal cortical margin (a); (2) mandibular thickness at the same level (b); (3) Buccolingual $ratio=(a)/(b){\times}100$; and (4) length between the inferior margin of the mandibular canal and the inferior cortical margin. Results: The distances from the canal to the buccal bone and from the canal to the inferior bone and mandibular thickness were significantly larger in Group II than in Group I. The buccolingual ratio of the canal was larger in Group II in the second molar region. Conclusion: If mandibular canal is in contact with the buccal cortical bone, the canal will run closer to the buccal bone and the inferior border of the mandible in the second and first molar regions.