• Imaging Science in Dentistry
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• 제43권3호
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• pp.153-161
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• 2013

Purpose: To prevent low bone mineral density (BMD), that is, osteoporosis, in postmenopausal women, it is essential to diagnose osteoporosis more precisely. This study presented an automatic approach utilizing a histogram-based automatic clustering (HAC) algorithm with a support vector machine (SVM) to analyse dental panoramic radiographs (DPRs) and thus improve diagnostic accuracy by identifying postmenopausal women with low BMD or osteoporosis. Materials and Methods: We integrated our newly-proposed histogram-based automatic clustering (HAC) algorithm with our previously-designed computer-aided diagnosis system. The extracted moment-based features (mean, variance, skewness, and kurtosis) of the mandibular cortical width for the radial basis function (RBF) SVM classifier were employed. We also compared the diagnostic efficacy of the SVM model with the back propagation (BP) neural network model. In this study, DPRs and BMD measurements of 100 postmenopausal women patients (aged >50 years), with no previous record of osteoporosis, were randomly selected for inclusion. Results: The accuracy, sensitivity, and specificity of the BMD measurements using our HAC-SVM model to identify women with low BMD were 93.0% (88.0%-98.0%), 95.8% (91.9%-99.7%) and 86.6% (79.9%-93.3%), respectively, at the lumbar spine; and 89.0% (82.9%-95.1%), 96.0% (92.2%-99.8%) and 84.0% (76.8%-91.2%), respectively, at the femoral neck. Conclusion: Our experimental results predict that the proposed HAC-SVM model combination applied on DPRs could be useful to assist dentists in early diagnosis and help to reduce the morbidity and mortality associated with low BMD and osteoporosis.

• 대한치과보철학회지
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• 제33권3호
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• pp.397-412
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• 1995

The purpose of this study was to analyze the stress distribution in the dentin and post structures by the various post core materials and the amount of remaining coronal tooth structures. The 2-dimensional finite element models of mandibular 2nd premolars was divided into seven types according to the various amount of remaining coronal tooth structures. All types were modeled using equal length, diameter and shape of the post. 2 types of post and core materials were used : 1) cast gold post and core 2) stainless steel post and compsite resin core 10 Newton force was applied as follows 1) vertical force on occlusal fossa 2) $45^{\circ}$ oblique force on buccal surface of buccal cusp tip The results were as follows : 1. There was no apparent difference in the pattern of stress distribution according to the amount of remaining coronal tooth structure. 2. There was no apparent difference in the pattern of stress distribution within the dentin according to the post and core materials. A cast gold post and core generated lower dentin stress than a stainless steel post and resin core. 3. Max. dentinal stress resulting from vertical force was observed in the lingual side of dentin around the crown margin.This stress resulting from oblique force was observed in the lingual root surface of alveolar bone crest level.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제33권1호
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• pp.77-82
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• 2011

A long-term follow-up study of a case of impacted teeth associated with a large dentigerous cyst in the left maxilla is presented. The patient was a 30-year-old man who had a large dentigerous cyst in the premaxilla and left posterior maxilla, which impacted the canine and supernumerary tooth. This is one of the most prevalent types of odontogenic cysts associated with an erupted or developing tooth, particularly the mandibular third molars. The other teeth commonly affected in order of frequency are the maxillary canines, maxillary third molars and rarely, the central incisor. Radiographically, the cyst appears as huge ovoid well-demarcated unilocular radiolucency with a sclerotic border and causes ectopic displacement of the inferior border of the maxillary sinus without destruction. Dentigerous cysts may grow unnoticed to such extensive sizes as to occupy a considerable portion of the maxillary sinus. These cysts appear to be associated with a supernumerary tooth in the maxillary anterior incisors region called the mesiodens and impacted canine. The present case report describes the surgical enucleation of a dentigerous cyst involving the permanent maxillary left canine and mesioden. After surgery, left maxillary sinus recovered their normal size and apposition of bone was observed around the apex of the posterior teeth. During the subsequent years, there was no recurrence of the cystic lesion but the inflammation was evoked in the anterior maxilla after 42 months. This complication appeared to have correlated with bony healing in the enucleation site of the cyst. We report the healing status of a huge dentigerous cyst in the maxilla for 5 years with a review of the relevant literature.

• Journal of Oral Medicine and Pain
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• 제16권1호
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• pp.33-72
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• 1991

The purpose of this study was to investigate the stress distribution and the displacement in the temporomandibular joints following the teeth loss patterns. The three dimensional finite element method was used for a mathematical model. The finite element model was composed of 1,632 elements and 2,411 nodes in the mandible with articular disc and mandibular fossa of the temporal bone. The masseter, the temporal and the internal pterygoid muscle forces were applied at each insertion site, bisecting point of gonion and antegonion, tip of the coronoid process, and gonion at the ration of 2:2:1 respectively. The directions of muscles force were obtained from frontal and lateral cephalometric tracings using bony landmarks of the skull. The results were as follows : 1. In control model, the minimum principal stresses were concentrated on the region of anterosuperior part of the condyle head and articular disc, and maximum principal stresses on the anterior part of the condyle head and posterolateral part of the articular disc. 2. In case of unilateral teeth loss, the greater principal stress appeared at the teeth loss side and the principal stresses increased at the teeth loss side as the number of the posterior teeth loss went up. 3. In case of bilateral teeth loss, the principal stresses were greater than those of the control model and as the number of the posterior teeth loss increased, the grater principal stresses on the temporomandibular joints appeared at the both side. 4. When the posterior teeth existed bilateral, the principal stress patterns were similar to those of the control model. 5. The displacement ws directed mainly upward and backward in the upper part of the temporomandibular joints and upward and forward in the largest part of the condyle head. The displacement increased as the number of the posterior teeth loss went up.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제28권6호
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• pp.586-589
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• 2006

Deep circumflex iliac artery (DCIA) flap can be harvested as a composite free flap and is often used to adequately reconstruct wide mandibular defects. However, the harvesting of this DCIA flap can result in severe osseous defect of the donor site causing a morphologic defect in the iliac crest. To reconstruct this defect of the iliac donor site, several innovative techniques using bioactive ceramic spacers, autogenous rib bone, polylactic acid mesh, or titanium plates have been introduced. Nonetheless, these methods have not been widely used due to high cost, secondary donor site morbidity, difficulty of use, and postoperative dissatisfaction. We used two titanium plates to reconstruct the donor iliac site defect at the harvesting time of primary DCIA flap surgery in the 30-year old female with an ameloblastoma in the left mandible. Postoperatively, both iliac sites were relatively balanced and there were few complications. At the 2 years follow-up, there were no specific abnormal radiographic findings and the patient was very satisfied with her esthetic iliac contouring. In our report, we evaluate the effect of two titanium plates on the reconstruction of the iliac donor site in the aspects of esthetics and usefulness. This technique has many advantages, such as reduced cost, simplicity, decreased postoperative pain or discomfort, and improved bilateral balance of both anterior iliac crest contours, especially in young female patients.

• 대한치과교정학회지
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• 제17권1호
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• pp.135-148
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• 1987

To investigate the relationship between craniofacial growth and bone maturity of the hand wrist in normal occlusion, the author took cephalogram and handwrist radiogram of 391 students (male 192, female 199) and assessed the measurements of cephalogram according to skeletal maturity stages of the hand and wrist. In this study, four skeketal stages and 36 linear, angular measurements of the cephalometrics were selected. In hand-wrist X-ray the bones used to determine skeletal maturity were the middle phalanges of the third finger, and distal epiphysis of the radius. In cephalogram, the landmark used to measure the angle and length were N, S, Po., Ar., Go., Me., Gn., Pog., Point B, Point A, ANS, PNS, Or., U1, L1, U6, L6 etc.. The results were as follows, 1. The table of mean, standard deviation, p-value from measurements were made in each group and both sex. 2. The increased measurements according to skeletal maturity were anterior cranial bese length, posterior cranial base length, ramus height, anterior facial height, posterior facial height, L1 to mandibular plane (mm), facial plane angle. In contrast to, decreased measurements were genial angle, facial cnvexity and facial plane angle. 3. Denture pattern measurements (IMPA, FMIA, occlusal plane to Go-Gn, interincisal angle, U1 to SN plane, U1 to SN plane, U1 to facial plane, L1 to facial plane etc.) .had nothing to do with skeletal maturity. 4. Skeletal maturity had close relationship with craniofacial growth, but had little to do with tooth development.

• 대한치과교정학회지
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• 제29권1호
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• pp.37-49
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• 1999

악관절 기능 장애는 교정치료 전,중 또는 후에 빈번하게 부딪치는 어려운 문제이다. 특히 장안모 고경군의 형태학적 특징상 악관절 기능이상이 쉽게 발현될수 있는 가능성을 갖고 있다. 이에 17세 이상의 여성중 SN-MP가 $38^{\circ}$ 이상인 장안모 유형 환자를 대상으로 악관절 기능 장애군 51명, 비장애군 42명을 대상으로 교정모형과 두부방사선 사진을 대상으로 통계처리하여 다음과 같은 결과를 얻었다. 1. 악관절 기능 장애군과 비장애군에서 수평 피개량과 수직 피개량은 통계적으로 유의한 차이를 보이지 않았다. 2. 악관절 기능 장애군과 비장애군에서 하악 평면에 대한 하악 제1대구치의 기울기 및 수직적 위치는 통계적으로 유의한 차이를 보였다. 3. 악관절 기능 장애군과 비장애군에서 기능적 요소로 두경부 자세, 혀, 및 설골의 위치는 통계적으로 유의한 차이를 보이지 않았다.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제29권2호
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• pp.135-139
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• 2003

저자 등은 본과에 내원하여 함치성 낭종으로 진단된 5명의 소아 환자에서 보존적인 조대술을 이용하여 매복된 영구치를 발거하지 않고 이차 치유를 유도하였다. 술 후 병소는 신생골로 치유되었으며 매복 영구치도 정상적인 위치로 맹출하였다. 이와 같이 소아에서 함치성 낭종의 경우 주기적인 예후 관찰이 가능하다면 보다 보존적인 조대술 등을 이용시에는 영구치의 정상적인 유도와 낭종의 치유를 유도할 수 있으리라 사료된다. 또한 인접치아의 경사 등에 의한 정상적인 치아의 맹출이 어려운 경우에는 교정치료와 병행시에 정상적인 영구 치열을 확보할 수 있을 것으로 사료되어 문헌고찰과 함께 보고하는 바이다.

• Imaging Science in Dentistry
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• 제46권3호
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• pp.167-171
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• 2016

Purpose: Obstructive sleep apnea (OSA) is a common medical disorder with serious complications if untreated. Dentists play a vital role in the early diagnosis of this condition, thereby improving patients' prognoses. The purpose of this study was to identify patients with a high risk of OSA using simple cephalometric measurements in patients receiving routine dental care. Materials and Methods: The present study was conducted on 206 patients divided into a high-risk group and a control group after answering the Berlin questionnaire. Cephalometric analysis of a digital cephalogram was performed to measure the upper airway diameter (UAD) and mandibular-to-hyoid bone distance (MP-H) by 2 observers at 2 different times. Results: Among 206 patients, 93 (45%) were included in the high-risk group and 113 (55%) were in the control group. No significant difference was present between the groups with regard to gender, and the patients ranged in age from 18 to 65 years. The UAD measurements in the high-risk group were significantly lower than in the control group, and the MP-H measurements were significantly higher in the high-risk group than in the control group. The UAD was lower in middle-aged patients in both groups. Conclusion: Our study found that the UAD was lower in individuals with a high risk of OSA. Also, we found that middle-aged individuals of both genders were more likely to develop OSA. Dentists play a vital role in diagnosing patients at a high risk for OSA via thorough clinical examinations, risk factor analyses, and simple cephalometric analyses.

• 대한두개안면성형외과학회지
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• 제9권2호
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• pp.105-109
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• 2008

악안면 수술에 있어서 악관절 및 교합은 미용적 측면에서 뿐만 아니라 그 기능적 측면에서 더욱 중요하다. 특히 하악이 고정된 경우뿐만 아니라 움직일 때 악관절 및 기능적 교합상태까지 보존 및 재건하고 정확한 수술을 하기 위해서 수술 전후에 적절한 MMF는 필수적이다. 이를 위해 저자들은 치열활봉에 대한 그 동안의 경험을 바탕으로 치열의 흐름에 대한 기본적 이론, 교합을 고려한 치열활봉의 거치방법 및 복잡한 교합평면을 가진 악안면 수술 환자들에 대해서 술전 인상을 이용한 치열활봉 거치법을 제안하는 바이다.