• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제36권4호
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• pp.262-269
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• 2010

Introduction: Accurate diagnosis and treatment planning are very important for orthognathic surgery. A small error in diagnosis can cause postoperative functional and esthetic problems. Pre-existing 2-dimensional (D) chephalogram analysis has a high likelihood of error due to its intrinsic and extrinsic problems. A cephalogram can also be inaccurate due to the limited anatomic points, superimposition of the image, and the considerable time and effort required. Recently, an improvement in technology and popularization of computed tomography (CT) provides patients with 3-D computer based cephalometric analysis, which complements traditional analysis in many ways. However, the results are affected by the experience and the subject of the investigator. Materials and Methods: The effects of the sources human error in 2-D cephalogram analysis and 3-D computerized tomography cephalometric analysis were compared using Simplant CMF program. From 2008 Jan to 2009 June, patients who had undergone CT, cephalo AP, lat were investigated. Results: 1. In the 3 D and 2 D images, 10 out of 93 variables (10.4%) and 11 out 44 variables (25%), respectively, showed a significant difference. 2. Landmarks that showed a significant difference in the 2 D image were the points frequently superimposed anatomically. 3. Go Po Orb landmarks, which showed a significant difference in the 3 D images, were found to be the artificial points for analysis in the 2 D image, and in the current definition, these points cannot be used for reproducibility in the 3 D image. Conclusion: Generally, 3-D CT images provide more precise identification of the traditional cephalometric landmark. Greater variability of certain landmarks in the mediolateral direction is probably related to the inadequate definition of the landmarks in the third dimension.

• 대한치과교정학회지
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• 제27권4호
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• pp.633-641
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• 1997

성장 또는 치료로 인한 악안면골의 변화는 두부 방사선을 중첩 함으로써 판단할 수 있다. 중첩에 대한 평가는 중첩방법에 따라 변화되므로 좀더 정확한 중첩 방법을 선택하는 것은 치료 효과에 대한 분석이나 성장 변화에 대한 평가를 정확히하는 선결 요건이 될것이다. 3년 정도의 비교적 짧은 성장기간을 가진 11세 전후의 여자 환자 19명을 대상으로, 가장 널리쓰이는 중첩 방법인 Nasion-Sells line중첩과 Bjork가 주장하는 Anteirior cranial base (ACB)중첩을 비교하여 다음과 같은 결론을 얻었다. 1 Nasion-Sells line중첩과 ACB중첩은 중첩오차(registration error)의 크기가 거의 같아서 reliability에 있어서 큰차이가 없는 것으로 나타났다 2. 검사자간 차이(interobserver difference)에 있어서 Nasion-Sells line중첩은 7개의 측정 항목 모두에서 두 검사자간에 차이가 없었으나 ACB중첩은 7개의 측정 항목중 4개의 측정 항목에서 두 검사자간 유의성 있는 차이가 나타났다. 3. 중첩방법의 차이 (intermethod difference)에 있어서 Nasion-Sella line중첩으로 측정한 계 측치와 ACB 중첩으로 측정한 계측치가 유의성있게 차이가 나지 않았다.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제21권4호
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• pp.353-359
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• 1999

Purpose : A new method of lateral cephalometric analysis for midface, focusing on zygomatic bone, was created in this study, and measured in Korean adults. The purposes of this study are understanding about new approach for midfacial depression, especially zygomatic bone, and using to make adequate diagnosis and treatment plan. Materials and methods : In this study, esthetic Korean adults, 25 males and 25 females who were between $0^{\circ}$ and $4^{\circ}$ in ${\angle}ANB$, and between 62% and 70% in P/A facial height ratio, and had normal overbite and overjet, were used. Orbitale(Or) and Soft tissue orbitale(Or') were used for indicators of anteroposterior position of zygomatic area. And, mean value and standard deviation of linear and angular measurements, and ratio about each linear measurements, were obtained. then, standard deviation diagram - wiggle diagram - was made for visualization of results. Results : Mean values, standard deviations and ranges of 19 measurements were obtained, and among them, 5 linear measurements that had large standard deviation were excluded and the others were used for making standard deviation diagram. In standard deviation diagram, the following results were obtained. 1. If the measurements are located on more left side of mean-value-vertical -line, the potential of midfacial hypoplasia are stronger, especially zygomatic area. 2. If the measurements are located on more right side of mean-value-vertical-line, the potential of midfacial hypoplasia are decreased. Conclusion : This study presented a new method of lateral cephalometric analysis focusing on zygomatic bone in Korean adults. We expect that the results of this study can be used as parameter when clinicians make decisions about diagnosis and treatment plan for rehabilitation of esthetics and function. But, it is necessary to prove its usefulness, and to further evaluate the results.

• Journal of Yeungnam Medical Science
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• 제18권2호
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• pp.208-214
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• 2001

성장기 3급 부정 교합인 남아 20명의 두부계측방사선 사진을 Harvold 분석법을 중심으로 하여 정상 대조군과 비교하여 다음과 같은 결론을 얻었다. 상하악간 상대적인 길이 차를 나타내는 악간 길이 차는 3급 부정교합자군에서 유의하게 더 크게 나타났다(p<0.05). 전하안면 고경은 3급 부정교합군에서 정상교합군보다 더 크게 나타났으나, 통계적으로 유의한 차는 없었다.

• Imaging Science in Dentistry
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• 제51권3호
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• pp.299-306
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• 2021

Purpose: This study aimed to propose a fully automatic landmark identification model based on a deep learning algorithm using real clinical data and to verify its accuracy considering inter-examiner variability. Materials and Methods: In total, 950 lateral cephalometric images from Yonsei Dental Hospital were used. Two calibrated examiners manually identified the 13 most important landmarks to set as references. The proposed deep learning model has a 2-step structure-a region of interest machine and a detection machine-each consisting of 8 convolution layers, 5 pooling layers, and 2 fully connected layers. The distance errors of detection between 2 examiners were used as a clinically acceptable range for performance evaluation. Results: The 13 landmarks were automatically detected using the proposed model. Inter-examiner agreement for all landmarks indicated excellent reliability based on the 95% confidence interval. The average clinically acceptable range for all 13 landmarks was 1.24 mm. The mean radial error between the reference values assigned by 1 expert and the proposed model was 1.84 mm, exhibiting a successful detection rate of 36.1%. The A-point, the incisal tip of the maxillary and mandibular incisors, and ANS showed lower mean radial error than the calibrated expert variability. Conclusion: This experiment demonstrated that the proposed deep learning model can perform fully automatic identification of cephalometric landmarks and achieve better results than examiners for some landmarks. It is meaningful to consider between-examiner variability for clinical applicability when evaluating the performance of deep learning methods in cephalometric landmark identification.

• Imaging Science in Dentistry
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• 제52권3호
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• pp.239-244
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• 2022

Purpose: Despite the proliferation of numerous morphometric and anthropometric methods for sex identification based on linear, angular, and regional measurements of various parts of the body, these methods are subject to error due to the observer's knowledge and expertise. This study aimed to explore the possibility of automated sex determination using convolutional neural networks(CNNs) based on lateral cephalometric radiographs. Materials and Methods: Lateral cephalometric radiographs of 1,476 Iranian subjects (794 women and 682 men) from 18 to 49 years of age were included. Lateral cephalometric radiographs were considered as a network input and output layer including 2 classes(male and female). Eighty percent of the data was used as a training set and the rest as a test set. Hyperparameter tuning of each network was done after preprocessing and data augmentation steps. The predictive performance of different architectures (DenseNet, ResNet, and VGG) was evaluated based on their accuracy in test sets. Results: The CNN based on the DenseNet121 architecture, with an overall accuracy of 90%, had the best predictive power in sex determination. The prediction accuracy of this model was almost equal for men and women. Furthermore, with all architectures, the use of transfer learning improved predictive performance. Conclusion: The results confirmed that a CNN could predict a person's sex with high accuracy. This prediction was independent of human bias because feature extraction was done automatically. However, for more accurate sex determination on a wider scale, further studies with larger sample sizes are desirable.

• Journal of Oral Medicine and Pain
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• 제47권3호
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• pp.135-143
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• 2022

Purpose: This study aimed to evaluate polysomnographic and cephalometric characteristics of patients with OSA according to obesity level based on the World Health Organization (WHO) Asian-Pacific BMI criteria. Methods: One hundred and thirty-one consecutive patients with obstructive sleep apnea (OSA) were evaluated using standard level 1 polysomnography and cephalometric analyses. The subjects were categorized into normal, overweight and obese groups according to the WHO Asian-Pacific BMI criteria. Respiratory indices and cephalometric parameters were compared among groups. Results: The 131 patients consisted of 111 males and 20 females, with a mean age of 44.1±12.4 years. The mean value of BMI was 25.3±3.4 kg/m² for all subjects, 20.6±2.2 kg/m² for normal (n=27), 24.0±0.5 kg/m² for overweight (n=33) and 27.6±2.2 kg/m² for obese (n=71). The obese group had a significantly higher apnea-hypopnea index (AHI) and respiratory arousal index and lower oxygen saturation level than the normal group (p<0.05). Total AHI, mean oxygen saturation level and respiratory arousal index were significantly correlated with BMI (p<0.001). A longer soft palate and anterior position of the hyoid bone were significantly correlated with BMI level (p ≤0.05). Conclusions: Obese patients have a higher risk of compromised craniofacial skeletal features and soft tissue structures, and severe OSA than non-obese patients.

• Imaging Science in Dentistry
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• 제31권4호
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• pp.199-204
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• 2001

Purpose : To assess the relationship between soft tissue asymmetry and bone tissue asymmetry using the standardized photographs and the posteroanterior (PA) cephalometric radiographs in mandibular asymmetric patients. And to clarify that the lack of morphologic balance among different skeletal components can often be masked by compensatory soft tissue contributions. Methods: Experimental group consisted of 58 patients whose chief complaints were facial asymmetry, they were taken with standardized facial photographs and PA cephalometric radiographs. Control group consisted of 30 persons in the normal occlusion. The reproducibility of the facial photograph was confirmed by model test. The differences of fractional vertical heightand horizontal width from standardized facial photographs and PA cephalometric radiographs were compared and analyzed. Results: The difference of fractional vertical bone height was 0.63 and fractional vertical soft height was 0.58 in control group, 3.10 and 2.01 in asymmetric group, respectively. The difference of fractional horizontal bone width was 0.52 and fractional horizontal soft width was 0.70 in control group, 2.51 and 1.70 in asymmetric group, respectively. Both soft and bone tissue showed significant difference between control and asymmetric group (p<0.05). The difference of bone tissue was greater than that of soft tissue (p<0.05) in the experimental group but, not in control group. Conclusions: Soft tissue components may compensate for underlying skeletal imbalances.

• 대한치과교정학회지
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• 제24권3호
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• pp.521-534
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• 1994

The purpose of this study was to compare the differences in measurements between cephalometric radiographs and digigraphs of Dolphin Imaging System. 26 Korean adult male and 24 adult female with normal occlusion were selected. For each subject lateral cephalogram was taken. Digitizing with Digigraph Work Station of Dolphin in System. was performed as well. 50 tracings and 50 digigraphs were analyzed with Yonsei, Ricketts, Burstone analyses. The comparable measurements between tracing group and digigraph group were statistically analyzed. The results were as follows: 1. 13 of 64 comparable measurements did not show any statistically significant difference (P>0.05) between tracing group and digigraph group. 2. Three of the measurements with FH plane as a reference plane did not show any statistically insignificant difference. All measurement with SN plane as a reference plane showed statistically significant difference(p<0.05). 3. The measurements which showhed no statistically significant difference were mostly short distance linear measurements while most of the angular measurements showed statistically significant difference(p<0.05).

• Maxillofacial Plastic and Reconstructive Surgery
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• 제18권2호
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• pp.184-199
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• 1996

The challenges to achieve three dimensional facial proportionality and occusal stability in many patients with complex dentofacial deformity have been met by the development and use of the maxilla, mandible, and chin surgery techniques in combination with efficient orthodontic treatment. There is a clinical, biological, and biomechanical foundation for simultaneous surgical repositioning of the maxilla, mandible, and chin in a significant proportion of adult and adolescent patients. A combination of the surgical and orthodontic approach may provide increased treatment efficiencies and optimal esthetic results. Art and science to determine the treatment objectives, specifically, the desired soft tissue changes are firstly established by using the clinician's "esthetic sense" of the facial beauty and proportion aided to a few cephalometric guidelines. In this sense, the dependence on the clinician's "esthetic eye" by Dr. Bell is more important in analyzing the facial proportion than the satisfaction of rigid cephalometric norms. The purpose of this article was to elucidate the indication for simultaneous surgical repositioning of the maxilla, mandible, and chin, and to describe the clinical cephalometric analysis for orthognathic surgery. Representative 6 case reports were presented and discussed to illustrate the esthetic, orthodontic, and surgical treatment objectives with long-term follow-up.