• The korean journal of orthodontics
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• v.51 no.4
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• pp.250-259
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• 2021

Objective: The aim of this study was to compare the differences in mandibular posterior anatomic limit (MPAL) distances stratified by vertical patterns in patients with skeletal Class III malocclusion by using cone-beam computed tomography (CBCT). Methods: CBCT images of 48 patients with skeletal Class III malocclusion (mean age, 22.8 ± 3.1 years) categorized according to the vertical patterns (hypodivergent, normodivergent, and hyperdivergent; n = 16 per group) were analyzed. While parallel to the posterior occlusal line, the shortest linear distances from the distal root of the mandibular second molar to the inner cortex of the mandibular body were measured at depths of 4, 6, and 8 mm from the cementoenamel junction. MPAL distances were compared between the three groups, and their correlations were analyzed. Results: The mean ages, sex distribution, asymmetry, and crowding in the three groups showed no significant differences. MPAL distance was significantly longer in male (3.8 ± 2.6 mm) than in female (1.8 ± 1.2 mm) at the 8-mm root level. At all root levels, MPAL distances were significantly different in the hypodivergent and hyperdivergent groups (p < 0.001) and between the normodivergent and hyperdivergent groups (p < 0.01). MPAL distances were the shortest in the hyperdivergent group. The mandibular plane angle highly correlated with MPAL distances at all root levels (p < 0.01). Conclusions: MPAL distances were the shortest in patients with hyperdivergent patterns and showed a decreasing tendency as the mandibular plane angle increased. MPAL distances were significantly shorter (~3.16 mm) at the 8-mm root level.

• Journal of the korean academy of Pediatric Dentistry
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• v.50 no.4
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• pp.469-482
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• 2023

This study aimed to investigate the treatment options for the delayed eruption of mandibular premolars and identify the predictors of spontaneous eruption using panoramic radiography. The prevalence of delayed mandibular premolar eruption in this retrospective analysis, comprising 254 patients (aged 9 - 15 years), was 5.19%, with no significant difference based on gender. The mandibular second premolars were most affected (4.39%) compared to the first premolars (0.76%). No significant difference in prevalence was observed between the left and right sides. Among the treated mandibular premolars, primary molar-related lesions were identified as the leading cause (7.85%) of delayed tooth eruption. The treatment duration varied based on the Nolla stage, eruption stage, and treatment method. Teeth with Nolla stage 7 or lower had a treatment duration of 22.89 ± 11.96 months, whereas those with stage 8 or higher had a 15.02 ± 6.34 month duration. The deeper the tooth was located in the bone, the longer the treatment period became. The treatment duration varied depending on the treatment method, and statistically, there was no significant difference. The treatment durations for affected mandibular premolars increased with the depth of impaction angle of inclination. In this study, the treatment duration for delayed eruptions varied depending on the Nolla stage, eruption stage, and treatment method. Variations in the impaction depth and inclination angle across various treatment approaches, as explored in this study, might offer valuable insights into the selection of the most suitable management options for delayed tooth eruptions.

• Imaging Science in Dentistry
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• v.54 no.2
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• pp.181-190
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• 2024

Purpose: This study compared sequential changes in skeletal stability and the pharyngeal airway following mandibular setback surgery involving fixation with either a titanium or a bioabsorbable plate and screws. Materials and Methods: Twenty-eight patients with mandibular prognathism undergoing bilateral sagittal split osteotomy by titanium or bioabsorbable fixation were randomly selected in this study. Lateral cephalometric analysis was conducted preoperatively and at 1 week, 3-6 months, and 1 year postoperatively. Mandibular stability was assessed by examining horizontal (BX), vertical (BY), and angular measurements including the sella-nasion to point B angle and the mandibular plane angle (MPA). Pharyngeal airway changes were evaluated by analyzing the nasopharynx, uvula-pharynx, tongue-pharynx, and epiglottis-pharynx (EOP) distances. Mandibular and pharyngeal airway changes were examined sequentially. To evaluate postoperative changes within groups, the Wilcoxon signed-rank test was employed, while the Mann-Whitney U test was used for between-group comparisons. Immediate postoperative changes in the airway were correlated to surgical movements using the Spearman rank test. Results: Significant changes in the MPA were observed in both the titanium and bioabsorbable groups at 3-6 months post-surgery, with significance persisting in the bioabsorbable group at 1 year postoperatively (2.29°±2.28°; P<0.05). The bioabsorbable group also exhibited significant EOP changes (-1.21±1.54 mm; P<0.05) at 3-6 months, which gradually returned to non-significant levels by 1 year postoperatively. Conclusion: Osteofixation using bioabsorbable plates and screws is comparable to that achieved with titanium in long-term skeletal stability and maintaining pharyngeal airway dimensions. However, a tendency for relapse exists, especially regarding the MPA.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.7 no.1
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• pp.39-42
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• 1977

Authors have obserbed a rare case of unilateral hypertrophy occured in the left mandibular condyle of 25 years old man. In the serial roentenograms, Authors have drawn following conclusions. 1. The patients face is markedly asymmetrical. This asymmetry consisted of an elongation and widening of the left mandibular ramus, neck and head of condyle which pushed the chin to the other side. 2. Left mandibular angle is flattened and mandibular inferior border is lower than right. 3. In the relationship of the left posterior teeth, severe mesioocclusion is occured.

• The Journal of Korean Academy of Prosthodontics
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• v.29 no.1
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• pp.39-52
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• 1991

The purpose of this study were to compare the condylar path and the anterior angle of glenoid fossae, and analyze the condylar path, and classify the patterns of condylar path. Thirty-three male and female dental students with normal occlusion and masticatory system ranging in age from 24 to 27, without present symptoms and any history of TM joint disturbance, were selected for this study. Then, sixty-six TM joint were examed. Transcranial radiographs of TM joint and Cephalometric radiographs under mandibular protrusive movement were obtained. They were taken at six positions on protrusive movement. The results obtained were as follows : 1. The sequence of the frequeny of condylar movement patterns were concave curve, "S"shape curve, convex curve, and reverse "S"shape. 2. The horizontal distance of the greatest changed position of condylar angle averaged 2.6mm. 3. The condylar path angle averaged 36.91 degree. 4. The angle of the anterior slope of glenoid fossae averaged 37.28 degree. 5. The distance fo condylar movement averaged 5.98mm and the distance of condylar horizontal movement averaged 4.71mm. 6. The slope of articular eminence was correlated to the condyalr path and three were no significant differences between right and left side of the anterior slope of articular eminence, and the condyalr path angle.

• The korean journal of orthodontics
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• v.28 no.6 s.71
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• pp.937-946
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• 1998

The patient with an anterior open bite has one of the most difficult orthodontic problem to correct. Previous studies have yielded different conclusions as to exactly where the morphologic problems associated with vertical dysplasia-high angle cases are located. In order to identify the cephalometric features of high angle cases and highlight the measurements that characterize high angle cases, 109 pretreatment cephalograms, 35 high angle, 37 average angle, and 37 low angle cases, were analyzed and compared statistically. As the mandibular plane was steeper, the anterior facial height, especially lower anterior facial height, became greater, and the posterior facial height became smaller. All the dentoalveolar vertical dimensions, especially in upper, increased. And all the skeletal angular measurements increased. Especially Lower genial angle had most positive correlation to mandibular Plane angle. Upper incisor was lingually inclined, and lower incisor was labially inclined in high angle cases.

• Imaging Science in Dentistry
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• v.36 no.1
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• pp.55-62
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• 2006

Purpose : To find the cause of root curvature by use of panoramic and lateral cephalometric radiograph. Materials and Methods : Twenty six 1st graders whose mandibular 1st molars .just emerged into the mouth were selected. Panoramic and lateral cephalometric radiograph were taken at grade 1 and 6, longitudinally. In cephalometric radio graph, mandibular plane angle, ramus-occlusal plane angle, gonial angle, and gonion-gnathion distance (Go-Gn distance) were measured. In panoramic radio graph, elongated root length and root angle were measured by means of digital subtraction radiography. Occlusal plane-tooth axis angle was measured, too. Pearson correlations were used to evaluate the relationships between root curvature and elongated length and longitudinal variations of all variables. Multiple regression equation using related variables was computed. Results : The Pearson correlation coefficient between curved angle and longitudinal variations of occlusal plane-tooth axis angle and ramus-occlusal plane angle was 0.350 and 0.401, respectively (p<0.05). There was no significant correlation between elongated root length and longitudinal variations of all variables. The resulting regression equation was $Y=10.209+0.208X_1+0.745X_2$ (Y: root angle, $X_1$: variation of occlusal plane-tooth axis angle, $X_2$: variation of ramus-occlusal plane angle). Conclusion : It was suspected that the reasons of root curvature were change of tooth axis caused by contact with 2nd deciduous tooth and amount of mesial and superior movement related to change of occlusal plane.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.14 no.4
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• pp.327-339
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• 1992

This study was undertaken to investigate the effect of orthognathic surgery on occlusal force. The maximum bite force was measured in 26 dentofacial deformity patients, aged 14-26(mean age 20.3) years, before surgery and at IMF removal, 3, 6, and 12months postsurgery. To grope the correlation of bite force and skeletal change after orthognathic surgery, the cephalometric headplates were measured, tabulated and statistically analyzed. The results were as follows. 1. The presurgical maximum bite force was 13.7kg in upper first molar(rt. Side 12.7kg, it. Side 14.6kg). There was remarkable difference with that of normal occlusion. 2. The recovery of bite force was very significant in according to the operation method and the duration of IMF that was 7.6kg at IMF removal, 14.2kg at 3 months, 19.7kg at 6 months. 26.1kg at 12 months postsurgery. 3. To fasten the recovery and to increase the bite force after orthognathic surgery, the long IMF time and the injury to the masticatory muscle should be avoided by the internal rigid fixation and early physical exercise. 4. The bite force was positively correlated to the changes of mandibular plane angle, the angle between platatal plane and mandibular plan, the angle between occlusal plane and mandibular plane, and negatively correlated to the changes of mandibular body length in craniofacial structure. 5. There was no correlationship between bit force and mesial inclination of tooth long axis of first molar in this subject. 6. There was no correlation between the changes of bite force and the changes of mechanical advantage of the temporal and masseter muscle.

• The korean journal of orthodontics
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• v.22 no.1
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• pp.205-227
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• 1992

This study was aimed to investigate the characteristics & the causative areas of the adult skeletal class III malocclusions with different facial divergency. The lateral cephalograms of 80 subjects with skeletal class III malocclusion from 17 to 29 years of age were classified into 3 groups according to SN-MP angle; hypodivergent group $(21.65{\pm}3.52^{\circ})$, neutrodivergent group $(30.50{\pm}2.29^{\circ})$ and hyperdivergent group $(40.02{\pm}3.98^{\circ})$. The data were gathered by digitizing of the traced cephalograms and were statistically analyzed. The results were as follows: 1. The anterior cranial base of the hyperdivergent group was shortest & tipped upwardly to the FH plane. 2. The maxilla of hyperdivergent group was shortest anteroposteriorly and positioned posteriorly to the anterior cranial base. 3. The degree of the mandibular prognathism in hyperdivergent group was less than the hypodivergent group. The hyperdivergent group showed the downward & backward rotated mandible. 4. The mandibular ramus & body was short & slender in the hyperdivergent group and the gonial angle was greatest in the hyperdivergent group. 5. The temporomandibular joint was positioned more superiorly to the anterior cranial base in the hyperdivergent group. 6. The cranial base, palatal plane, occlusal plane and mandibular plane were diverged in the hyperdivergent group. And this group had a great anterior total facial height, especially anterior lower facial height. 7. The craniofacial characteristics of skeletal class III malocclusion were critical in the vertical structure than the horizontal.

• Imaging Science in Dentistry
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• v.39 no.2
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• pp.81-87
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• 2009

Purpose: To evaluate the anteroposterior length and buccal angle of the anterior loop, and the size and location of the mental foramen using cone beam computed tomography (CBCT). Materials and Methods: 100 CBCT images from 87 adults (43 males and 44 females) ranging in age from 20 to 73 years (average 50 years) with edentulous ridge of the mandibular premolar region were obtained. Axial, sagittal, coronal images were reconstructed from Dental and Block Images of CBCT. The anteroposterior length, shape and buccal angle of the anterior loop, and the size and location of the mental foramen were calculated from reconstructed images of axial, sagittal and coronal CBCT. Results: The anteroposterior length and buccal angle of the mental canal was 4.0${\pm}$1.2mm, 37.8${\pm}$11.60$^{\circ}$respectively. The loop type with straight course was the most common shape of the mental canal. The location of the mental foramen below the apex of the lower second premolar (78%) was the most common. The maximum size of the mental foramen was 4.6${\pm}$1.0 mm in width and 3.0${\pm}$0.6 mm in height. The inner size of the mental canal was 2.6${\pm}$0.6 mm in width and 2.1 mm${\pm}$0.4 mm in height. Conclusion: CBCT is useful to evaluate the anterior loop and mental foramen of the mandibular canal. Safe guideline of 4 mm from the most anterior point of the mental foramen is recommended for implant and surgical treatment. (Korean J Oral Maxillofac Radiol 2009; 39: 81-7)