Comparison of measurements from digital cephalometric radiographs and 3D MDCT-synthetized cephalometric radiographs and the effect of head position

Purpose : To investigate the reproducibilities and compare the measurements in digital and MDCT-synthesized cephalometric radiograph, and to investigate the effect of head position on the measurement during imaging with MDCT. Materials and Methods : Twenty-two dry skulls (combined with mandible) were used in this study. Conventional digital cephalometric radiograph was taken in standard position, and MDCT was taken in standard position and two rotated position (10°left rotation and 10°right tilting). MDCT data were imported in OnDemand® and lateral cephalometric radiograph were synthesized from 3D virtual models. Two types of rotated MDCT data were synthesized with default mode and with corrected mode using both ear rods. For all six images, sixteen angular and eleven linear measurements were made in V-Ceph® three times. Reproducibility of measurements was assessed using repeated measures ANOVA and ICC. Linear and angular measurements were compared between digital and five MDCTsynthesized images by Student t-test. Results : All measurements in six types of cephalometric radiograph were not statistically different under ICC examination. Measurements were not different between digital and MDCT-synthesized images (P> .05). Measurements in MDCT-synthesized image in 10°left rotation or 10°right tilting position showed possibility of difference from digital image in some measurements, and possibility of improvement via realignment of head position using both ear rods. Conclusion : MDCT-synthesized cephalometric radiograph can substitute conventional cephalometric radiograph. The error on head position during imaging with MDCT have possibility that can produce measurement errors with MDCT-synthesized image, and these position error can be corrected by realignment of the head position using both ear rods. (Korean J Oral Maxillofac Radiol 2009; 39 : 133-47

Development and application of stent-based image guided navigation system for oral and maxillofacial surgery

Purpose : The purpose of this study was to develop a stent-based image guided surgery system and to apply it to oral and maxillofacial surgeries for anatomically complex sites. Materials and Methods : We devised a patient-specific stent for patient-to-image registration and navigation. Threedimensional positions of the reference probe and the tool probe were tracked by an optical camera system and the relative position of the handpiece drill tip to the reference probe was monitored continuously on the monitor of a PC. Using 8 landmarks for measuring accuracy, the spatial discrepancy between CT image coordinate and physical coordinate was calculated for testing the normality. Results : The accuracy over 8 anatomical landmarks showed an overall mean of 0.56±0.16 mm. The developed system was applied to a surgery for a vertical alveolar bone augmentation in right mandibular posterior area and possible interior alveolar nerve injury case of an impacted third molar. The developed system provided continuous monitoring of invisible anatomical structures during operation and 3D information for operation sites. The clinical challenge showed sufficient accuracy and availability of anatomically complex operation sites. Conclusion : The developed system showed sufficient accuracy and availability in oral and maxillofacial surgeries for anatomically complex sites. (Korean J Oral Maxillofac Radiol 2009; 39 : 149-56)grant of the Korea healthcare technology R & D Project Ministry for Health. Welfare & Family Affairs. Republic of Korea(A08-4491-AL2023-08N1-00030B)

교정용 미니 임플랜트의 디자인 및 drilling size 에 따른 식립 토크의 비교

학위논문 (석사)-- 서울대학교 대학원 : 치의학과, 2012. 2. 김태우.1. 목적 교정용 미니 임플랜트의 성공적인 식립을 위해서는 초기 안정성의 확보가 매우 중요하다. 초기 안정성이 확보되지 않으면 미니 임플랜트의 동요도가 증가하고, 이에 따라 골 유착에 실패해 미니 임플랜트가 탈락 할 가능성이 높아지기 때문이다. 이러한 초기 안정성을 평가하는 방법 중의 하나가 미니 임플랜트의 식립 토크를 측정하는 것이다. 교정용 미니 임플랜트에 회전 방지턱을 추가 하여 디자인에 변화를 주거나 또는 식립 전 drilling size 의 변화를 통해서 식립 토크의 차이를 관찰 하고, 이를 통해 미니 임플랜트의 적절한 회전 방지턱 디자인과 drilling size 를 알아보는 것이 본 연구의 목적이다. 2. 방법 본 연구에는 길이 및 외경, 내경이 일정한 단일 나사산의 원통형 교정용 미니 임플랜트를 사용했다. 미니 임플랜트를 회전 방지턱이 없는 대조군 (Group A) 과 회전 방지턱의 디자인이 각기 다른 3가지 실험군 (Group B, C, D) 으로 나누어 총 4개 group 으로 분류했다. 각 group 에 30개 씩 총 120 개의 미니 임플랜트를 식립했다. 미니 임플랜트 식립 시에 pre-drilling 여부와 pilot hole size 에 의한 최대 식립 토크의 변화를 관찰하기 위해 4개 군의 미니 임플랜트를 각각 pre-drilling 없이, 1.0 mm pre-drilling, 1.3 mm pre-drilling 으로 나누어 실험했다. 식립 부위에 따른 골 밀도 및 피질 골의 두께 차이를 배제하기 위해 2 mm 의 균일한 피질골 두께와 균일한 골 밀도를 가진 실험용 인조골 (Sawbones®, Pacific Research Laboratories, Inc., Vashon, WA, USA) 을 이용하였다. 사람 구강의 피질 골과 해면 골의 밀도를 재현하기 위해 solid rigid polyurethane foam 에 solid rigid polyurethane foam sheet 를 부착하였다. 임플랜트의 식립 시에는 외과용 엔진을 이용하여 일정한 속도를 유지하면서 식립을 시행하였고, 식립과 동시에 최대 식립 토크 및 식립 시간을 측정하였다. 정확한 식립 토크를 측정하기 위해 매 식립 전 calibration 과정을 거쳤으며, 측정된 데이터를 two-way ANOVA 방법을 사용하여 분석하였다. 3. 결과 회전 방지턱의 디자인에 따른 최대 식립 토크를 비교한 결과, 식립 전 drilling 여부나 drilling size 에 상관없이 Group D 에서 가장 작은 값이 나왔고, 회전 방지턱을 넣지 않은 Group A 에서 가장 높은 값을 보였다 (p < 0.05). Group B, C 는 중간 값을 보였고 통계적으로 유의하였다. 식립 전 drilling 이 최대 식립 토크에 미치는 영향을 살펴보면, 회전 방지턱의 유무와 디자인에 상관없이 1.3 mm pre-drilling 시에 가장 작은 값이 나왔고, pre-drilling 이 없을 때에는 가장 큰 값을 나타냈다 (p < 0.05).Purpose : It is very important to secure initial stability for successful placement of a mini-implant. This study aims to change the design of the orthodontic mini-implant by adding the vertical groove to it and observe the difference of the maximum insertion torque through the changes of the drilling size before insertion. Method : 120 Cylindrical orthodontic mini-implants with a single screw thread were divided into 4 groups : a control group with no vertical groove (Group A) and 3 experimental groups with different vertical groove designs (Group B, C, & D). The mini-implants were tested without pre-drilling and with 1.0 mm and 1.3 mm pre-drilling each. A surgical engine was used to maintain a constant rate during insertion, and the insertion torque. To measure the insertion torque accurately, each went through the calibration process before insertion, and the measured data were analyzed by using two-way ANOVA. Result : According to the result of comparing maximum insertion torques by the designs of vertical grooves, Group D showed the lowest value regardless of the drilling before insertion or drilling size, and the control group without any vertical groove indicated the highest value. Group B and C showed a medium value (p 〈 0.05). Examining the effects of pre-drilling on the maximum insertion torque, this study found that it was the lowest at 1.3 mm pre-drilling regardless of the existence of an vertical groove or design, and it was the greatest when there was no pre-drilling (p 〈 0.05). Conclusion : The design of vertical groove and pre-drilling size affect the maximum insertion torque of orthodontic mini-implants.Maste

유한 요소 해석을 이용한 하악골과 재건된 비골에 식립된 임플란트의 비교

학위논문 (박사)-- 서울대학교 대학원 : 치의학대학원 치의학과, 2018. 8. 권호범.Purpose: The purpose of this study was to compare dental implants placed in mandible and reconstructed fibula under the same loading conditions using three-dimensional finite element analysis. Materials and methods: Two three-dimensional finite element models were developed to analyze biomechanical behaviors of implants placed in mandible and reconstructed fibula. Mandible model was composed of the mandibular segment, implant systems, and two-unit splinted implant-supported crowns. Fibula model included the same components except that the mandible was replaced with a reconstructed fibula. In the implant-abutment joint with abutment screw, preload was achieved. Oblique loading of 150 N was applied to the occlusal surfaces of the splinted crowns at 11.54 degrees to apico-coronal direction. The stress distribution patterns and the maximum von Mises stress of the individual components were compared. Results: In the supporting bones, stress was concentrated in the cortical bone around the implant neck. After screw tightening and before the imposition of oblique loads, the pattern and values of the von Mises stresses were similar between the mandible and fibula models. The highest von Mises stresses in the cortical bone were 6.7 MPa in the mandible model and 7.1 MPa in the fibula model. After application of oblique loads, the highest von Mises stresses in the cortical bone were 11.5 MPa in the mandible model and 25.2 MPa in the fibula model. In the implant systems, the highest stress concentration was observed in the abutment screws in all models. After screw tightening and before the application of oblique loads, the stress distributions of the two models were similar to the ones before loading. The highest von Mises stresses in the abutment screws and abutments were 115.7 MPa in the mandible model and 115.1 MPa in the fibula model. After application of oblique loads, the maximum von Mises stress on the implants was 113.5 MPa in the mandible model and 116.2 MPa in the fibula model. Conclusion: Within the limits of this study, the splinted implant-supported fixed prosthesis placed in the reconstructed fibula might be a successful treatment option for the patient who underwent mandibular reconstruction based on biomechanical behaviors.Ⅰ. INTRODUCTION Ⅱ. MATERIALS AND METHODS Ⅲ. RESULTS Ⅳ. DISCUSSION Ⅴ. CONCLUSION REFERENCES KOREAN ABSTRACTDocto

돼지 하악골의 기계적 강도 예측시 2차원과 3차원 골미세구조간의 관계

Thesis(doctoral)--서울대학교 대학원 :치의학과 구강악안면방사선학전공,2006.Docto

Study of threshold and opacity in three-dimensional CT volume rendering of oral and maxillofacial area

Purpose: This study was designed to determine a proper threshold value and opacity in three-dimensional CT volume rendering of oral and maxillofacial area. Materials and Methods: Three-dimensional CT data obtained from 50 persons who were done orthognatic surgery in department of oral and maxillofacial radiology of Seoul National University retrospectively. 12 volume rendering post-processing protocols of combination of threshold(100HU, 150HU, 221HU, 270HU) and opacity (58%, 80%, 90%) were applied. Five observers independently evaluated image quality using a five-point range scale. The results were analyzed by receiver operating characteristic curves, ANOVA and Kappa value. And three oromaxillofacial surgeons chose the all images that they thought proper clinically in the all of images. Results: Analysis using ROC curves revealed the area under each curve which indicated a diagnostic accuracy. The highest diagnostic accuracy appear with 100HU and 58% opacity. and the lowest diagnostic accuracy appear with 221HU and 58% opacity that are being used protocol in department of oral and maxillofacial radiology of Seoul National University. But, no statistically significant difference was noted between any of the protocols. And the number of proper images clinically that chosen by three oromaxillofacial surgeons is the largest in the cases of protocol 8 (221HU, opacity 80%) and protocol 11 (270HU, opacity 80%) in one after the other. Conclusion: Threshold and opacity in volume rendering can be controled easily and these can be causes of making an diagnostic accuracy. So we need to select proper values of these factors

Recurrent odontogenic keratocyst within the masticatory space

The odontogenic keratocyst (OKC) is a developmental odontogenic cyst typically occurring in the jaws. Since the first description of OKC was published in 1956, the lesion has been of particular interest because of its specific histopathologic features, high recurrence rate, and aggressive behavior. Recurrences most commonly arise within bone at the site of the original cyst. However, as lining cells may find their way into surrounding tissues either from implantation during surgery or from cortical perforation recurrences may arise at a distance from the original cyst. Here, we report a rare case of recurrent OKC which was first developed in mandible and recurred within the masticatory space

Relationship between trabecular strength and three-dimensional architecture in the pig mandible using microcomputed tomography

Purpose : To investigate the relationship between three-dimensional (3D) bone imaging parameters and trabecular strength in the mandible. Materials and Methods : Bone specimens were obtained from the mandibles of five male pigs weighing around 110 kg each. Of those, 43 samples were selected for 3D analysis and measured by micro-computed tomography. The five morphometric parameters were trabecular thickness (Tb.Th), bone specific surface (BS/BV), percent bone volume (BV/TV), structure model index (SMI) and degree of anisotropy (DA). Through destructive mechanical testing, strength parameters were obtained. Results : BV/TV, SMI, BS/BV, and Tb.Th showed significant correlations with strength parameters. DA did not show any correlation with the other parameters. In multiple linear regression analysis, BV/TV alone explained 43% of the variance in Young's modulus. By stepwise inclusion of SMI, the variance in the Young's modulus was better explained up to 52%. Conclusions : Predicting trabecular strength in the mandible through architectural analysis would be possible. Further study is needed to establish the tendency and variety of trabecular architecture and strength according to the locations within the mandible

Study on the hard tissue changes in osteomyelitis of the jaws using CT image

Purpose : To assess the clinical findings and hard tissue changes of osteomyelitis of the jaws using computed tomographic (CT) image analysis. Materials and Methods : We reviewed and interpreted the CT images of 163 patients (64 males and 99 females, age range from 10 to 87 years) who visited the Seoul National University Dental Hospital from April 23, 2006 to December 31, 2008 and were diagnosed as osteomyelitis of the jaws through clinical, radiologic, and histopathologic examination. Each CT findings was investigated for frequency, correlation with age and gender. Results : Of the 163 patients, 31 (19.0%) were affected on the maxilla, 135 (82.8%) were affected on the mandible, and 3 (1.8%) were affected on the both jaws simultaneously. The mean age of the patients who were affected on the maxilla was 61.0 years and that of the patients who were affected on the mandible was 56.2 years. On the maxilla, the most frequent site of disease was the posterior area (83.9%) and on the mandible, mandibular body (83.0%), followed by angle (48.1%), ramus (38.5%), condyle (13.3%), incisal area (9.6%), and coronoid process (3.0%). Among the 31 maxillary osteomyelitis, defect in the trabecular bone was observed in 28 (90.3%), osteosclerosis 20 (64.5%), defect in the cortical bone 27 (87.1%), sequestrum 17 (54.8%), and periosteal reaction 2 (6.5%). Among the 135 mandibular osteomyelitis, defect in the trabecular bone was observed in 100 (74.1%), osteosclerosis 104 (77.0%), defect in the cortical bone 116 (85.9%), sequestrum 36 (26.7%), and periosteal reaction 67 (49.6%). Conclusion : Of our cases, the maxillary osteomyelitis was visibly observed more frequently in females than males. The incidence is the highest in seventies (28.8%) and the lowest in teens (3.1%). The osteomyelitis of the jaws was observed more frequently in males than females before the age of 50, and observed more frequently in females after the age of 50. The most noticeable point was that the sequestrum was observed more often on maxillary osteomyelitis and the periosteal reaction was observed more often on mandibular osteomyelitis

Differential Diagnosis of Oral Lesions for the Initial Diagnosis of Acute Lymphoblastic Leukemia

Careful examination of the oral cavity may reveal findings indicative of an underlying systemic condition, and allow for early diagnosis and treatment. Examination should include evaluation for mucosal changes, periodontal inflammation and bleeding,and general condition of the teeth. A 12-year-old man visited for molar pain during 3 months. He was diagnosed with having a possibility of hematopoietic malignancy, showing the loss of lamina dura, destruction of bony crypt, and high attenuation in the bone marrow. He was referred to department of pediatrics, additional study, including peripheral cell morphology and bone marrow exam, were performed, and diagnosed as acute lymphoblastic anemia. Despite chemotherapy to cure leukemia,he was expired 8 months after initial diagnosis. The purpose of this report is to promote and evoke the awareness regarding an initial examination of the dentist to make an effort to acquire accurate knowledge and information about life-threatening disease in usual dental practice.N