• 치과방사선
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• 제11권1호
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• pp.23-32
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• 1981

The purpose of this study was to assess temporomandibular joint subluxation by means of cephalometry using two lateral cephalograms from each person with in centric occlusion and wide-open mouth position, and to compare patient group with subluxation to normal control group in the measurements and correlation coefficient. The 200 cephalograms of 100 Korean adults, patient group consisted of 24 females and 26 males ranged from 17 to 63 years age and the normal control group consisted of 20 females and 30 males ranged from 18 to 56 years age, were studied and analyzed statistically. The results were as follows; 1. In the comparison of patient group vs normal control group in the measurements, statistically significant differences were found in C-C', C'-PTM, K-FH, K-PTM, Gn-Gn', C-S-C', Gn-S-Gn', Gn-K-Gn', GoGn-SN, and GoGn-Go'Gn'. K-point* of patient group was located antero - superiorly than of normal control group, and the significance level was higher in K-PTM than in K-FH. There was no statistically significant difference found in local relationship of C-point between patient group and normal control group. The values of correlation coefficient among all measurements were in 0.958≥r≥-0.760, and the highest value was in Gn-Gn' to GoGn-Go'Gn' and Gn-K-Gn' to Gn-Gn', and the lowest value was in C'-PTM to Gn-K-Gn' of normal control group. K was determined as a point of intersection by a perpendicular bisector of Gn-Gn' and a perpendicular bisector of C-C'.

• 대한치과교정학회지
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• 제51권2호
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• pp.77-85
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• 2021

Objective: To evaluate the accuracy of a multi-stage convolutional neural network (CNN) model-based automated identification system for posteroanterior (PA) cephalometric landmarks. Methods: The multi-stage CNN model was implemented with a personal computer. A total of 430 PA-cephalograms synthesized from cone-beam computed tomography scans (CBCT-PA) were selected as samples. Twenty-three landmarks used for Tweemac analysis were manually identified on all CBCT-PA images by a single examiner. Intra-examiner reproducibility was confirmed by repeating the identification on 85 randomly selected images, which were subsequently set as test data, with a two-week interval before training. For initial learning stage of the multi-stage CNN model, the data from 345 of 430 CBCT-PA images were used, after which the multi-stage CNN model was tested with previous 85 images. The first manual identification on these 85 images was set as a truth ground. The mean radial error (MRE) and successful detection rate (SDR) were calculated to evaluate the errors in manual identification and artificial intelligence (AI) prediction. Results: The AI showed an average MRE of 2.23 ± 2.02 mm with an SDR of 60.88% for errors of 2 mm or lower. However, in a comparison of the repetitive task, the AI predicted landmarks at the same position, while the MRE for the repeated manual identification was 1.31 ± 0.94 mm. Conclusions: Automated identification for CBCT-synthesized PA cephalometric landmarks did not sufficiently achieve the clinically favorable error range of less than 2 mm. However, AI landmark identification on PA cephalograms showed better consistency than manual identification.

• 대한치과교정학회지
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• 제51권1호
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• pp.15-22
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• 2021

Objective: The aim of this study was to evaluate the correlation between the vertical position of maxillary first molar and vertical skeletal measurements in lateral cephalograms by using new linear measurements on the vertical axis of coordinates with calibration. Methods: The vertical position of maxillary first molar (U6-SN), and the conventionally used variables (ConV) and the newly derived linear variables (NwLin) for vertical skeletal patterns were measured in the lateral cephalograms of 103 Korean adults with normal occlusions. Pearson correlation analyses and multiple linear regression analyses were performed with and without calibration using the anterior and posterior cranial base (ACB and PCB, respectively) lengths to identify variables related to U6-SN. Results: The PCB-calibrated statistics showed the best power of explanation. ConV indicating skeletal hyperdivergency was significantly correlated with U6-SN. Six NwLin regarding the position of palatal plane were positively correlated with U6-SN. Each multiple linear regression analysis generated a two-variable model: sella and nasion to palatal plane. Among the three models, the PCB-calibrated model yielded highest adjusted R2 value, 0.880. Conclusions: U6-SN could be determined by the vertical position of the maxilla, which could then be used to plan the amount of molar intrusion and estimate its clinical stability. Cephalometric calibration on the vertical axis of coordinates by using PCB for vertical linear measurements could strengthen the analysis itself.

• 대한치과교정학회지
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• 제52권2호
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• pp.112-122
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• 2022

Objective: This study aimed to present and evaluate a new deep learning model for determining cervical vertebral maturation (CVM) degree and growth spurts by analyzing lateral cephalometric radiographs. Methods: The study sample included 890 cephalograms. The images were classified into six cervical stages independently by two orthodontists. The images were also categorized into three degrees on the basis of the growth spurt: pre-pubertal, growth spurt, and post-pubertal. Subsequently, the samples were fed to a transfer learning model implemented using the Python programming language and PyTorch library. In the last step, the test set of cephalograms was randomly coded and provided to two new orthodontists in order to compare their diagnosis to the artificial intelligence (AI) model's performance using weighted kappa and Cohen's kappa statistical analyses. Results: The model's validation and test accuracy for the six-class CVM diagnosis were 62.63% and 61.62%, respectively. Moreover, the model's validation and test accuracy for the three-class classification were 75.76% and 82.83%, respectively. Furthermore, substantial agreements were observed between the two orthodontists as well as one of them and the AI model. Conclusions: The newly developed AI model had reasonable accuracy in detecting the CVM stage and high reliability in detecting the pubertal stage. However, its accuracy was still less than that of human observers. With further improvements in data quality, this model should be able to provide practical assistance to practicing dentists in the future.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제34권6호
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• pp.421-425
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• 2012

Purpose: The aim of this study is to compare the soft tissue changes of the midfacial area at the repose position and the natural smiling position for the improvement of evaluation and planning in the orthognathic surgery. Methods: The total of 30 subjects, 15 male and 15 female, were included in this study. The metal point landmarks were placed at the cheek, orbital rim, subpupil, and nasal base. The movements of the landmarks were evaluated at the repose position and smiling position in the lateral and posteroanterior cephalograms. Paired t test and correlation analysis were used for the evaluation of the soft tissue changes statistically. Results: In the lateral cephalograms, the cheek point (4.49 mm in female, 4.87 mm in male) showed the most distant movement. All points presented significant movements, except the orbital rim and nasal base point in male. Cheek point presented significant positive correlation between the horizontal and vertical change in male. Subpupil point presented significant positive correlation between horizontal and vertical change in both male and female. In the posteroanterior cephalograms, the nasal base point (5.41 mm in female, 6.30 mm in male) showed the most distant movement. Subpupil point and nasal base point presented significant movements in both female and male. Nasal base point presented significant negative correlation between the horizontal and vertical change in both male and female. In the lateral and posteroanterior cephalograms, the positional changes of all points presented significant positive correlation with each other in both female and male. Conclusion: The cheek point in the sagittal view and the nasal base point in the frontal view showed the most distant movement on smile. In the sagittal view, the subpupil point and cheek point moved anteriorsuperiorly on smile. In the frontal view, the nasal base points moved laterosuperiorly on smile. In both the sagittal and frontal view, the positional changes of all point were highly correlated to each other. These results may be used in the soft tissue references for the treatment planning of the dentofacial deformity patients.

• 대한치과교정학회지
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• 제17권2호
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• pp.321-333
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• 1987

The purpose of this study was to observe the changes of the lower 3rd molars following the extraction of the lower 2nd molars by Lateral Cephalograms and Orthopantomograms. The subjects consisted of twenty malocclusion, 7 males 13 females, were 19 year 5 month old at the removal of the lower 2nd molars, 19 year 1 month old at the end of the orthodontic supervision after the removal of the lower 2nd molars (mean age) The obtained results were as follows, 1 It is recommended to extract the lower 2nd molars when the lower 3rd molars are Nolla's Stage 4 or 5 2 With the pre-extraction variables obtained by factor analysis, it was possible to predict the long axis of the lower 3rd molars after 2nd molar extraction. 3 There were no impacted 3rd molars.

• 대한치과교정학회지
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• 제21권2호
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• pp.447-455
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• 1991

This research was carried out in order to study the effects of Rapid Maxillary Expansion on maxilla and it's surrounding skeletal structures. The sample for this study consists of 14 patients who were in retention period after rapid maxillary expansion. Following results were obtained after performing comparative analysis of cephalograms taken before and after rapid maxillary expansion. 1. In almost every cases, inferior displacement of palatal planes with concurrent changes in their inclination were observed. 2. Changes in the inclination of palatal plane can be categorized into inferiorty inclined group, superiorly inclined group and constant group in relation to the states before rapid masillary expansion. 3. Decrease in < Se-FMN/PMV and increase in < Se-FMN-A were evident in the superiorly inclined group and vice versa for the inferiorly inclined group.

• 대한치과교정학회지
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• 제10권1호
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• pp.65-70
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• 1980

The purpose of this study was giving some helpful datas in analysing the degree of anteroposterior jaw disharmony with the 'Wits' appraisal. The cephalograms of 105 Korean adults with normal occlusion ranging from 17 to 20 years of age and 76 Koreans with various malocclusion ranging from 12 to 24 years of age were studied and analyzed statistically. The results were as follows; 1. The mean value of 'Wits' appraisal in normal occlusion group was -0.82mm in males and -0.17mm in females. 2. There was no significant difference between the males and females in normal occlusion group. 3, The mean value of 'Wits' appraisal in Angles class II malocclusion group was 2.67mm and higher than normal group. 4. The mean value of 'Wits' appraisal in Angles class III malocclusion group was -8.11 mm and lower than normal group.

• 대한치과교정학회지
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• 제13권2호
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• pp.201-204
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• 1983

To study the calcification of second molars in Class I malocclusion with normal craniofacial structure, the author examined cephalograms, orthopantomograms, periapical films of 538 children from 7 y 0 m to 15y 11m old who had Class I malocclusion with normal craniofacial structure, and observed the calcification stage of upper and lower second molars. The results are as follows. 1. The mean ages of crown completion of upper and lower second molars are $8.82{\pm}1.14,\;8.72{\pm}0.75$ in boys, and $8.60{\pm}1.46,\;8.22{\pm}0.92$ in girls. 2. The mean ages of root completion of upper and lower second molars are $14.25{\pm}1.46,\;14.15{\pm}0.83$ in boys, and $14.12{\pm}0.93,\;14.15{\pm}0.83$ in girls. 3. There are no difference between the calcification stages of upper second molars and those of lower second molars in both sexes.

• 대한치과교정학회지
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• 제22권2호
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• pp.475-481
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• 1992

The purpose of this study was to examine the displacement of glenoid fossa during growth, and to investigate the relationship between the displacement of glenoid fossa and mandible. Pretreatment and posttreatment lateral cephalograms of 41 patients (male : 13, female : 28) were obtained from the orthodontic clinics of Wonkwang university hospital and were analized in terms of the position of articulare and mandible and statistically. The obtained results were as follows, 1. Aritculare was displaced posteriorly and inferioly during craniofacial growth and development. 2. The more posteriorly articulare displaced, the less anteriorly pogonion displaced, but the more inferiorly menton displancd. 3. The more posteriorly or inferiorly articulare was located, the more inferiorly menton displaced, and the more posteriorly articulare was located posteriorly, the less cant of the mandibular plane.