• 대한치과보철학회지
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• 제33권2호
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• pp.335-353
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• 1995

The purpose of this study was to the determine the optimal torques values to tighten the retaining screw. 3-different implant system tested were as follows : Branemark implant system$(3.75mmD{\times}100mm)$, Steri-Oss implant system$(3.8mmD{\times}10mm)$. One fixtures of each implant system was mounted into the epoxy resin block and abutment/superstructure complex was constructed. Eighty dental college students(male : 40, female : 40) of Chosun University were selected and were asked to tighten the retaining screws. Abutment/superstructure complex of each implant system was tightened to the maximum torque by use of hand-held screw driver, and then torque value was measured with torque value was measured with torque driver(Tohnichi torque driver, model 20 FTD, Tohnichi MFG, Co., LTD., Tokyo, Japan). Abutment/superstructure complex of each implant system was titghtened to each torque of 10 N-cm, 20 N-cm and 30 N-cm, and then the dynamic load(vertical & diagonal load) was applied to the abutment / superstructure complex. The gap between abutment/superstrure in each implant system was measured with 3-dimensional measuring microscope(model No. 850, Germany). The results were as follow : 1. Torque values according to the individual subjects showed wide range. 2. Torque values according to sex showed statistical significant difference. Those are as follows : in case of male, $9.38{\pm}2.93$ N-cm ; incase of female, $7.80{\pm}2.25$ N-cm. 3. Torque values according t implant systems showed statistical significant difference. Those are as follows : in ase of Branemark implant system, $6.54{\pm}1.54$ N-cm : in ase of Steri-Oss implant system, $10.1{\pm}2.88$ N-cm ; in case of IMZ implant system, $9.18{\pm}2.17$ N-cm. 4. The more torque value of tightening screw was increased, the less the gap was after the vertical and diagonal loading. 5. The gap after the diagonal loading was greater than that after the vertical loading. 6. The magnitude of gap between abutment/superstructure in order of IMZ, Steri-Oss, Branemark implant system after the verical and diagonal loading. 7. The gap under the diagonal loading after applying 30 N-cm torque showed no statistical significant difference in cases of the Branemark system and the Steri-Oss implant system but it showed significant different in case of the IMZ implant system.

• 구강회복응용과학지
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• 제21권2호
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• pp.153-167
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• 2005

The purpose of this study was to compare the v-shape thread with the square shape thread of fixture in the view of stress distribution pattern using finite element stress analysis. The finite element model was designed with the parallel placement of two standard fixtures(4.0 mm diameter ${\times}$ 11.5 mm length) on the region of mandibular 1st and 2nd molars. Three dimensional finite element model was created with the components of the implant and surrounding bone. This study simulated loads of 200 N at the central fossa in a axial direction (load A), 200 N at the buccal offset load that is 2 mm apart from central fossa in a axial direction (load B), 200 N at the buccal offset load that was 4 mm apart from central fossa in a axial direction (load C). These forces of load A',B',C' were applied to a $15^{\circ}$ inward oblique direction at that same site with 200 N. Von Mises stress values were recorded and compared in the supporting bone, fixture, and abutment screw. The following results have been made based on this study : 1. The highest stress concentration occurred at the cervical region of the implant fixture. 2. Von Mises stress value of off-site region was higher than that of central fossa region. 3. Square shape thread type showed more even stress distribution in the vertical and oblique force than V-shape thread type. 4. Stress distribution was the most effective in the case of buccal offset load (2, 4 mm distance from central fossa) in the square shape thread type. 5. V-shape thread type revealed higher von Mises stress value than square shape thread type in all environmental condition. The results from numerical analyses concluded that square shape thread type had the lower destructive stress and more stress distribution between the fixture and bone interface than V-shape thread type. Therefore, square shape thread type was regarded as optimal thread configuration in biomechanical concepts.

• 구강회복응용과학지
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• 제20권2호
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• pp.83-94
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• 2004

The purpose of this study was to compare the distributing pattern of stress according to the types of occlusal load on the finite element models of the splinted implant prostheses. The finite element model was designed with the parallel placement of two fixtures ($4.0mm{\times}11.5mm$) on mandibular first and second molars. The cemented crowns for mandibular first and second molars were made. Three-dimensional finite element model was created with the components of the implant, surrounding bone and cemented crowns. Two types of occlusal load, the point load and the surface load within 0.5 mm radius circle, were applied to the finite element models with 200N magnitude in axial(along the long axis of the implant and oblique(angulation of $30^{\circ}$ to the long axis) directions perpendicular to cuspal incline. Loads were positioned from the center of central fossa and to distance of 2 mm and 4 mm apart from the center of central fossa. Von-Mises stresses were recorded and compared in the fixtures and sections. The results were as following : 1. Under axial loading at the central fossa, the stress was distributed along the fixture except for the apical portion, not relative to both point & surface contacts. 2. With offset distance increasing, the highest stresses were concentrated in the neck portion of the fixture. 3. The maximum von Mises stress under the oblique load was greater than that under the axial load. 4. Under the oblique load, the highest stress were concentrated in the buccal side and lingual neck portion of the fixture with offset distance increasing. The results had a tendency to increase the stress on the neck portion of fixture with the offset and oblique loads increasing. The design of occlusal scheme should be allowed to distribute stress axially in maximum intercuspation and to decrease the angulation of cuspal incline.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제33권2호
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• pp.112-119
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• 2011

Purpose: Collagen membranes are used extensively as bioabsorbable barriers in guided bone regeneration. However, collagen has different effects on tissue restoration depending on the type, structure, degree of cross-linking and chemical treatment. The purpose of this study was to evaluate the inflammatory reaction, bone formation, and degradation of dehydrothermal treated porcine type I atelocollagen (CollaGuide$^{(R)}$) compared to of the non-crosslinked porcine type I, III collagen (BioGide$^{(R)}$) and the glutaldehyde cross-linked bovine type I collagen (BioMend$^{(R)}$) in surgically created bone defects in rat mandible. Methods: Bone defect model was based upon 3 mm sized full-thickness transcortical bone defects in the mandibular ramus of Sprague-Dawley rats. The defects were covered bucolingually with CollaGuide$^{(R)}$, BioMend$^{(R)}$, or BioGide$^{(R)}$ (n=12). For control, the defects were not covered by any membrane. Lymphocyte, multinucleated giant cell infiltration, bone formation over the defect area and membrane absorption were evaluated at 4 weeks postimplantation. For comparison of the membrane effect over the bone augmentation, rats received a bone graft plus different covering of membrane. A $3{\times}4$ mm sized block graft was harvested from the mandibular angle and was laid and stabilized with a microscrew on the naturally existing curvature of mandibular inferior border. After 10 weeks postimplantation, same histologic analysis were done. Results: In the defect model at 4 weeks post-implantation, the amount of new bone formed in defects was similar for all types of membrane. Bio-Gide$^{(R)}$ membranes induced significantly greater inflammatory response and membrane resorption than other two membranes; characterized by lymphocytes and multinucleated giant cells. At 10 weeks postoperatively, all membranes were completely resorbed. Conclusion: Dehydrotheramal treated cross-linked collagen was safe and effective in guiding bone regeneration in alveolar ridge defects and bone augmentation in rats, similar to BioGide$^{(R)}$ and BioMend$^{(R)}$, thus, could be clinically useful.

• 대한치과교정학회지
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• 제40권4호
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• pp.250-259
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• 2010

상악 구치의 후방이동을 위한 구강 내 장치 중 환자의 협조를 필요로 하지 않는 방법은 제II급 부정교합의 개선에 성공적으로 널리 사용되고 있다. 본 연구는 스크류에 의해 지지되는 구강 내 후방이동 장치를 소개하고 그 효율성을 조사하고자 하였다. Angle Class II 부정교합으로 진단된 21명의 환자(여자 11명, 남자 10명; 평균 연령 14.9세)를 대상으로 하였다. 2개의 스크류를 incisive foramen 후방에 식립하고, 식립한 즉시 힘을 주어 상악 제1대구치의 후방이동에 사용하였다. 상악 구치를 후방이동시켜 제I급 구치관계를 얻기 위해 스크류에 의해 지지되는 구강 내 후방이동 장치를 사용하였다. 치료 전후 측모두부 방사선 사진과 3차원 모델 분석을 통해 골격 및 치아의 변화를 평가하였다. 연구결과 상악 구치는 평균 3.95 mm 후방이동하였고, 추가적인 고정원 소실 없이 제I급 구치관계를 확립하였다. 상악 대구치는 $1.49^{\circ}$ 후방경사 되었고, 회전된 정도는 좌우 각각 $0.74^{\circ}$, $0.54^{\circ}$으로 통계적으로 유의성 있는 변화를 보이지 않았다 (p > 0.05). 새롭게 고안된 장치는 스크류에 의해 지지되어 환자의 협조도를 요하지 않으며 특별한 고정원 소실 없이 구치의 치체이동을 통한 후방이동을 얻는 데 효과적인 것으로 판단된다.

• Journal of Microbiology and Biotechnology
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• 제26권10호
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• pp.1817-1823
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• 2016

Areca nut (AN) chewing is a habit in many countries in Central, Southern, and Southeast Asia. It is strongly associated with the occurrence of oral, pharyngeal, and esophageal cancer as well as systemic inflammation. However, the association between AN intake and the development of gastric lesions has not yet been identified. The aim of this study was to investigate the effect of AN on gastric diseases using a mouse model for Helicobacter pylori infection. We studied four groups of mice: those fed a normal diet (ND), those fed a diet containing 2.5% AN (AD), those fed ND and infected with H. pylori PMSS1 strain (ND/HP), and those fed AD and infected with H. pylori PMSS1 strain (AD/HP). Food intake and body weight were monitored weekly during the experiments. At 10 weeks, the mice were sacrificed, and the stomach weight, H. pylori colonization, and gastric inflammation were evaluated. The stomach weight had increased significantly in the ND/HP and AD/HP groups along with increases in H. pylori colonization; however, there was no significant difference between these two groups with respect to stomach weight and colonization. On histological grading, mononuclear cell infiltration was severer in the AD/HP group than in the ND/HP group. These data suggest that chronic gastric inflammation was aggravated by AN treatment in the mice with H. pylori-induced gastric lesions. Furthermore, as previously suggested, this animal model is useful to determine the effect of potential carcinogens on gastric lesions induced by H. pylori infection.

• Imaging Science in Dentistry
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• 제45권1호
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• pp.15-22
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• 2015

Purpose: This study was performed to assess the reproducibility of identifying the sella turcica landmark in a three-dimensional (3D) model by using a new sella-specific landmark reference system. Materials and Methods: Thirty-two cone-beam computed tomographic scans (3D Accuitomo$^{(R)}$ 170, J. Morita, Kyoto, Japan) were retrospectively collected. The 3D data were exported into the Digital Imaging and Communications in Medicine standard and then imported into the Maxilim$^{(R)}$ software (Medicim NV, Sint-Niklaas, Belgium) to create 3D surface models. Five observers identified four osseous landmarks in order to create the reference frame and then identified two sella landmarks. The x, y, and z coordinates of each landmark were exported. The observations were repeated after four weeks. Statistical analysis was performed using the multiple paired t-test with Bonferroni correction (intraobserver precision: p<0.005, interobserver precision: p<0.0011). Results: The intraobserver mean precision of all landmarks was <1 mm. Significant differences were found when comparing the intraobserver precision of each observer (p<0.005). For the sella landmarks, the intraobserver mean precision ranged from $0.43{\pm}0.34mm$ to $0.51{\pm}0.46mm$. The intraobserver reproducibility was generally good. The overall interobserver mean precision was <1 mm. Significant differences between each pair of observers for all anatomical landmarks were found (p<0.0011). The interobserver reproducibility of sella landmarks was good, with >50% precision in locating the landmark within 1 mm. Conclusion: A newly developed reference system offers high precision and reproducibility for sella turcica identification in a 3D model without being based on two-dimensional images derived from 3D data.

• Journal of Periodontal and Implant Science
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• 제48권5호
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• pp.305-316
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• 2018

Purpose: The aim of the present study was to evaluate the biocompatibility and barrier function of mussel adhesive protein (MAP)-loaded collagen membranes in guided bone regeneration (GBR). Methods: Eight male New Zealand white rabbits were used. Four circular defects (diameter: 8 mm) were created in the calvarium of each animal. The defects were randomly assigned to 1) a negative control group, 2) a cyanoacrylate (CA)-loaded collagen membrane group (the CA group), 3) a MAP-loaded collagen membrane group (the MAP group), and 4) a group that received a polycaprolactone block with MAP-loaded collagen membrane (the MAP-PCL group). Specimens were harvested at 2 weeks (n=4) and 8 weeks (n=4) postoperatively for observational histology and histometric analysis. Results: In the histologic analysis, MAP was completely absorbed without any byproducts. In contrast, some of the CA adhesive remained, showing an inflammatory reaction, at 8 weeks. In the MAP-PCL group, the MAP-loaded collagen membranes served as a barrier membrane despite their fast degradation in GBR. No significant difference was found in the amount of new bone between the MAP-PCL and MAP groups ($1.82{\pm}0.86mm^2$ and $2.60{\pm}0.65mm^2$, respectively). Conclusions: The MAP-loaded collagen membrane functioned efficiently in this rabbit calvarial GBR model, with excellent biocompatibility. Further research is needed to assess clinical applications in defect types that are more challenging for GBR than those used in the current model.

• 대한치과보철학회지
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• 제53권4호
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• pp.330-336
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• 2015

목적: 본 연구의 목적은 치간 유두의 소실로 인해 치아 사이에 언더컷이 존재하는 경우 이것이 인상체의 정확도에 영향을 미치는지 알아보고자 하는 것이다. 재료 및 방법: 2종류의 부가중합형 실리콘 인상재($Extrude^{(R)}$ Wash, $Imprint^{TM}$ II Quick Step Light Body)와 한 종류의 알지네이트 인상재(Cavex Impressional)로 상악 주모형의 인상을 채득하여 얻은 실험모형상의 두 점 사이의 거리를 측정하여 주모형과 비교하여 모형의 변형 정도를 측정하였다. 세 종류의 인상재에서 얻은 실험 모형들을 치간 유두가 존재하는 군과 존재하지 않는 군으로 나눠 총 6개의 군을 평가하였으며, 각 군당 6개의 모형을 측정하였다. 삼차원 광학 스캐너로 실험모형을 스캔한 후, 하나의 모형당 6개의 두 점 사이의 거리를 삼차원 디지털 계측 소프트웨어 상에서 측정하였다. 측정 거리의 변화 정도를 백분율로 계산하여 모형의 변형률을 구하였으며, 이것을 이원분산분석을 이용하여 유의수준 .05에서 분석하였다. 결과: 측정거리 6개 중 3개에서 인상재에 따라 통계적으로 유의한 차이를 보였다. 반면, 치간 유두의 존재 여부에 따른 차이는 알지네이트 인상재에서 하나의 측정 거리에서만 유의한 차이를 보였을 뿐(P=.047), 다른 측정거리들과 인상재에서는 통계적으로 유의성 있는 차이를 나타내지 않았다. 결론: 치간 유두의 소실로 인한 언더컷의 존재가 부가중합형 실리콘 인상재와 알지네이트 인상재의 체적 정확도에 미치는 영향은 크지 않았다.

• 대한치과보철학회지
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• 제45권5호
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• pp.653-664
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• 2007

Statement of problem: The screw detorque value is a measure of the preload remaining in the screw just before detorquing. Purpose: This study evaluated the effect of different screw tightening sequences and tightening methods on detorque values for a well-fitting implant superstructure. Material and method: An implant superstructure that connected directly to four implants (Astra Tech) was fabricated on a fully edentulous mandibular acrylic resin model. Six well-fitting dental stone casts were made with a pickup impression of the superstructure from the acrylic resin model. To evaluate the effect of three screw tightening sequences (1-2-3-4, 2-4-3-1, and 2-3-1-4) and two tightening methods (2-step and 1-step) on the stability of screw joint, the detorque values for a well-fitting implant superstructure were measured twice after screw tightening using 20 Ncm. Detorque values were analyzed using multi-way analysis of variance and two-way analysis of variance at a .05 level of significance. Results: 1. The mean detorque values for three screw tightening sequences were 12.3 Ncm, 12.6 Ncm, and 12.0 Ncm, respectively. 2. The mean detorque values for two screw tightening methods were 12.0 Ncm, and 12.2 Ncm, respectively. 3. The mean of mimimum detorque values for three screw tightening sequences and for two tightening methods were 10.6 Ncm, 11.1 Ncm, 10.5 Ncm, and 9.8 Ncm, respectively. 4. No statistically significant differences among the variables of screw tightening sequence and tightening method were found (p>.05) for detorque values and for mimimum detorque values. Conclusion: Within the limitations of this study, the screw tightening sequence and tightening method did not have a significant effect on the detorque values for a well-fitting implant superstructure.