• Maxillofacial Plastic and Reconstructive Surgery
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• 제13권4호
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• pp.476-490
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• 1991

Although various technical details of the surgical procedures have been improved, Skeletal relapse is the most noteworthy complication of orthognathic surgery. It seems to be an imbalance of the perioral muscular groups resulting from changes in the cavitas oris propria after surgery. Among other factors, it is widely known with the changes of tongue posture, as indicated by the hyoid position. Ten patients that had undergone mandibular setbacks by way of Modified Obwegeser method were evaluated retrospectively. The serial cephalometric films were taken preoperatively, immediately postoperatively, after removal of IMF, and at a subsequent long-term follow-up period. The cephalometric evaluation of tongue posture were based on stable craniofacial landmarks. The relation between the 2-dimensional changes of tongue posture and hyoid position and the relapse of mandibular setback are discussed. Anatomic changes that were found to accompany such setback are as follows. 1.There are 2 cases of relapse in 10 patients at long-term follow-up(20%) 2.The tongue was moved posteriorly and its size was reduced anteriorly and posteriorly at immediate postoperative change and then the mandible shifted slightly toward the preoperative position, but the long was adapted to its new environment due to changing the position of its posterior part, and also the hyoid that moved posterioly and inferiorly was stabilized sightly posteriorly than its original position. 3.On the distance change of the suprahyoid muscle, the distance of P-H, ST-H was increased at immediate postoperative change(p<0.01) and decreased at IMF period(p<0.001), but the distance of H-Me, H-Ge was slightly decreased at IMF and long-term period(p<0.05). 4.On the width change of the pharyngeal air way, the width of the upper part of the pharyngeal space was lightly contracted at IMF and long-term period(p<0.05). 5.On the relation between mandibular setback and tongue posture and hyoid position, the significant correlation was found between the changes of some parts of mandibular setback and those of tongue posture, and not found those of hyoid position.

• Imaging Science in Dentistry
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• 제40권2호
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• pp.75-81
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• 2010

Purpose : This study is aimed to evaluate the position of mandibular foramen of mandibula prognathism patients using 3-dimensional CT images in order to reduce the chance of an anesthetic failure of the mandibular nerve and to prevent the damage to the inferior alveolar nerve during the orthognathic surgery. Materials and Methods : The control group consist of 30 patients with class I occlusion. The experimental group consist of 44 patients with class III malocclusion. Three-dimensional computed tomography was used to evaluate the position of the mandibular foramina. Results : The distance between mandibular plane and mandibular foramen, class I was 25.385 mm, class III was 23.628 mm. About the distance between occlusal plane and mandibular foramen, class I was 1.478 mm, class III was 5.144 mm. The distance between posterior border plan of mandibular ramus and mandibular foramen had not statistically significant. About the distance between sagittal plane of mandible and mandibular foramen did not also showed statistically significant. Conclusion : The result of this study could help the clinicians to apprehend more accurate anatomical locations of the foramina on the mandible with various facial skeletal types. thereby to perform more accurate block anesthesia of the mandibular nerve and osteotomy with minimal nerve damage. In addition, this study could provide fundamental data for any related researches about the location of the mandibular foramina for other purposes.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제19권4호
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• pp.351-361
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• 1997

This study was performed to evaluate the change of the soft tissue facial profile after mandibular set back surgery during time intervals. For this study, 33 patient, 8 males and 25 females, were selected and their lateral cephalograms were taken and analyzed periodically. Hard and soft tissue changes during postoperative time intervals, correlation between surgical skeletal changes and postoperative soft tissue changes, and prediction for long-term soft tissue changes were established through varying statistical methods. The results were as follow : 1. There were meaningful changes of anteroposterior skeletal position at 6 months and 2 years after mandibular set back by mandibular ramus osteotomy. Two years postoperatively, there was 30%, 32%, 29% relapse on B point, pogonion, menton each. 2. Two years after the mandibular ramus osteotomy, the relative changes of the soft tissue to their osseous counterparts showed 76% on the lower lip and 91% on the pogonion. 3. The movements of the mandibular landmarks in correlation to anteroposterior position of the lower lip and soft tissue of the chin showed to be effective on a long-term basis. 4. Using surgical changes of pogonion, prediction of changes in soft and hard tissue pogonion was useful and the coefficient of determination was 0.46 each and their reliability decreased 2 years postoperatively. 5. The upper lip position after the mandibular set back surgery was somewhat anterior 2 years postoperatively, but that has no statistical meanings.

• Journal of Oral Medicine and Pain
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• 제20권1호
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• pp.159-169
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• 1995

The purpose of this study was investigating the effects of pivot splint on width of the temporomandibular joint space in order to get the basic data for clinical applications. Pivot splint could be used for treating the patients with temporomandibular disorders, especially for chronic closed lock which would not be reduced by joint manipulation or with other methods. So it is necessary to have a lot of underlying data for using pivot splint, but there is few available reports related to mechanical principle or clinical results of the splint. Healthy twenty dental students wee collected for this study and pivot splint with 2.5mm high right-side pivot was used. Next, transcanial projection was taken and width of joint space at there mandibular positions were measured : habitual occlusion position, clenching position with splint, and clenching position with splint and mandibular force. The data were processed with SAS statistical program. The obtained results were as follows : 1. Ipsilateral posterior joint space width was increased on clenching the pivot splint, but joint space widths of contralateral side were not significantly changed. 2. Superior and posterior joint space width were increased on clenching the pivot splint with mandibualr force on both ipsilateral and contralateral side. 3. Ipsilateral joint space widths were not significantly changed from habitual occlusion position to clenching the pivot splint with active mandibular force, but in case of with passive mandibular force, posterior joint space width was significantly increased. 4. Correlationships between mandibular positions were more significant at anterior joint space than at superior or posterior joint space. But the correlation between clenching and clenching with mandibular force was significant at all the three joint space.

• 대한치과보철학회지
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• 제27권2호
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• pp.143-154
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• 1989

The purpose of this study was to investigate the mandibular opening and closing movements at mandibular incisor region and clinical rest position in normal subject using the newly developed electric mandibular movement analyzing device, (M.K.G.-K6 diagnostic system, Myo-tronics Inc. Seattle, WA, U.S.A.) The 58 normal subjects, who were students of the College of Dentistry, Chonbuk National University, were selected according to sampling criteria. The obtained results were as follows: 1. There was no significant difference of distribution of opening and closing movement patterns at mandibular incisor region between male and female. There was significant difference between habitual and maximum movement patterns both in sagittal and frontal plane. 2. Although the percentage of distribution of crossover pattern was highest in all cases, but there were significant differences between patterns only at habitual opening and closing movement in sagittal plane. 3. The mean of maximum opening was $47.29{\pm}4.68mm$ in male and $42.15{\pm}4.95mm$ in female. Therefore the mean of maximum opening was larger in male than in female. 4. The mean of maximum laterotrusion in frontal trajectory was larger to the left than to the right. Also the proportion of left deviation at maximum opening position was larger than that of other cases. 5. The mean of maximum opening and closing velocity was higher in male than in female and the mean of closing velocity was higher than that of opening velocity. Also the amount of separation from the centric occlusion was higher in maximum closing velocity than in maximum opening velocity. 6. Clinical rest position was $1.70{\pm}0.99mm$ inferior, $0.74{\pm}0.57mm$ anterior, $0.99{\pm}0.51mm$ right from centric occlusion and the A/V ratio was 1:2.7.

• 대한치과교정학회지
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• 제47권1호
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• pp.21-30
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• 2017

Objective: The aim of this study was to investigate the three-dimensional (3D) position of the center of resistance of 4 mandibular anterior teeth, 6 mandibular anterior teeth, and the complete mandibular dentition by using 3D finite-element analysis. Methods: Finite-element models included the complete mandibular dentition, periodontal ligament, and alveolar bone. The crowns of teeth in each group were fixed with buccal and lingual arch wires and lingual splint wires to minimize individual tooth movement and to evenly disperse the forces onto the teeth. Each group of teeth was subdivided into 0.5-mm intervals horizontally and vertically, and a force of 200 g was applied on each group. The center of resistance was defined as the point where the applied force induced parallel movement. Results: The center of resistance of the 4 mandibular anterior teeth group was 13.0 mm apical and 6.0 mm posterior, that of the 6 mandibular anterior teeth group was 13.5 mm apical and 8.5 mm posterior, and that of the complete mandibular dentition group was 13.5 mm apical and 25.0 mm posterior to the incisal edge of the mandibular central incisors. Conclusions: Finite-element analysis was useful in determining the 3D position of the center of resistance of the 4 mandibular anterior teeth group, 6 mandibular anterior teeth group, and complete mandibular dentition group.

• Imaging Science in Dentistry
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• 제50권2호
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• pp.125-132
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• 2020

Purpose: The positions of the mandibular foramen (MnF) and the lingula affect the success rate of inferior alveolar nerve block. The objective of this study was to investigate aspects of the MnF and the lingula relevant for mandibular block anesthesia using cone-beam computed tomography (CBCT). Materials and Methods: Fifty CBCT scans were collected from a picture archiving and communications system. All scans were taken using an Alphard Vega 3030 (Asahi Roentgen Co. Ltd., Kyoto, Japan). Fifty-eight MnFs of 30 subjects were included in the study. The position of the MnF, the size of the MnF, the position of the lingula, the size of the lingula, and the shape of the lingula were measured and recorded. All data were statistically analyzed at a significance level of P<0.05. Results: The position of MnF was 0.1 mm and 0.8 mm below the occlusal plane in males and females, respectively. The horizontal position of the MnF was slightly anterior to the center of the ramus in males and in the center in females (P<0.05). The vertical position of the MnF was lower in females than in males(P<0.05). The MnF was an oval shape with a longer anteroposterior dimension. The height of the lingula was 9.3 mm in males and 8.2 mm in females. The nodular type was the most common shape of the lingula, followed by the triangular, truncated, and assimilated types. Conclusion: CBCT provided useful information about the MnF and lingula. This information could improve the success rate of mandibular blocks.

• 대한치과교정학회지
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• 제23권4호
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• pp.693-705
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• 1993

The purpose of this study was to investigate the functional adaptation of the tongue, the hyoid bone, the digastric muscle and the upper airway and the variables predicting postoperative stability following orthognathic surgery in patients with mandibular prognathism. 18 patients were selected(8 men and 10 women) for this study, who had received orthognathic surgery. Their lateral cephalograms, those were taken preoperatively, immediate postoperatively and over 6 months follow-up, were traced and analysed. The results were as follows : 1. The downward displacement of the hyoid bone and extended head posture were recognized, right after operation. Statistically significant correlations were found between the changes of the mandibular position and the digastric muscle and the change of head posture during operation. 2. The tongue was displaced downward following the hyoid displacement postoperatively. Statistically significant correlations were found between the change of the mandibular position and the change of the distance of the tongue and hard palate, and between the change of head posture and the changes of the upper airway sizes, the digastric muscle and the hyoid position during over 6 month's follow-up. 3. The change of the distance of the tongue and hard palate was the most significant factor for prognosis during over 6 month's follow-up. 4. There were no variables before operation to predict the postoperative stability and the constriction of the upper airway.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제22권4호
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• pp.411-419
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• 2000

Purpose: This study was aimed at analysis of the changes in the condyle position in subjects with mandibular setback osteotomies Method: Twenty patients were evaluated retrospectively for their changes in the condyle position who underwent surgical mandibular setback using bilateral sagittal split osteotomies with a manual condyle repositioning technique and rigid fixation. The cephalometric and panoramic analysis was performed preoperatively, 1 week, 6 months, and 1 year postoperatively. And postoperative noise, temporomandibular joint pain, and mouth opening were clinically examined 2 months, 4 months, 6 months, 8 months, 10 months, and 12 months postoperatively. Result: The condyles rotated posteriorly and laterally immediately after surgery, and they returned to the preoperative position during follow-up period but it is not significant. The statistical analysis (Paired t-test) showed no significant effects in postsurgical stability. The changes in the condyle position didn't have a significant harmful influence on temporomandibular joint disorder. Conclusion: A careful surgical mandibular setback using manual condyle repositioning and fixation technique will move condyle minimally and that will decrease the relapse and temporomandibular joint disorder.

• 대한치과교정학회지
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• 제23권4호
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• pp.633-644
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• 1993

There has been so much controversies about the position of upper and lower jaws, and their first permanent molars in normal occlusion and Angle's class $I{\cdot}II{\cdot}III$ malocclusions. So, the purpose of this study is to compare the position of upper and lower jaws, and their first molars in normal occlusion and Angle's class $I{\cdot}II{\cdot}III$ malocclusions by lateral cephalometric analysis. The sample consisted of one hundred and twenty girls(thirty in each group) who had completed growth. The findings of this study were as follows : 1. In class I malocclusion, both maxilla and mandible were slightly posterior position than normal occlusion, but they showed harmonious relationship. 2. In class II malocclusion, the mandible was greatly retruded, and the maxilla was also slightly retruded to the cranial base as compared with normal occlusion. 3. In class III malocclusion, the maxilla was significantly retruded to the cranial base, but no significant difference was found in mandibular position as compared with normal occlusion. 4. The maxillary first molar was located at posterior position in class II malocclusion, and anterior position in class III malocclusion to the cranium, so that the rotation of mandible was influenced by that. 5. The mandibular first molar showed constant relationship to the mandible in all four groups, but different position to the cranial base in direct proportion to the mandibular position. 6. On the treatment planning of class III malocclusion, it seems to be better to promote the mandibular horizontal growth by inhibiting the vertical growth of maxillary molar area, and on the treatment planning of class III malocclusion, it seems to be better to promote the antero-inferior growth of maxilla mi to promote the mandibular vertical growth by inducing the vertical growth of maxillary molar area.