• 치위생과학회지
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• 제15권1호
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• pp.12-17
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• 2015

본 연구에서는 치과 CAD/CAM 시스템을 이용하여 SM 가공 방식으로 코핑을 제작 후 주조한 금속 코핑과, AM 가공 방식으로 코핑을 제작 후 주조한 금속 코핑과의 변연 및 내면 적합도를 비교 평가하여 다음과 같은 결과를 얻었다. SM 가공 방식과 AM 가공 방식의 변연 적합도 부분에서는 $120{\mu}m$ 임상적 허용 범위에 존재하였다. SM 가공 방식과 AM 가공 방식의 변연 적합도 및 내면 적합도는 통계적으로 유의한 차이가 있는 것으로 나타났다(p<0.05). SM 가공 방식과 AM 가공 방식으로 제작된 두 그룹의 전체 적합도와 4부분 부위별 적합도 측정은 SM 가공 방식보다 AM 가공 방식이 우수하였다. 결론적으로 금속 코핑의 변연 및 내면 적합도는 SM 가공 방식보다 AM 가공 방식이 우수하였고, 그 결과 값들은 임상적 허용범위 안에 존재하였다. 앞으로 치과분야에서 AM 가공 방식에 관한 연구는 계속되어야 하며, 보다 완성도 높은 금속 코핑 제작이 가능하다고 생각된다.

• 대한치과교정학회지
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• 제30권5호
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• pp.565-578
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• 2000

한국인의 치열의 특성을 고려한 Straight-Wire Appliance(SWA)의 제작을 위한 자료를 얻기 위하여 18세 이상 25세 사이의 한국인 성인 정상교합자를 1) 구강악안면부에 기능장애가 없고, 2) 양호한 치열궁 형태와 긴밀한 구치부 교합관계를 가지며, 3) 교합이 전후방적으로 앵글 분류 I 급의 관계를 가지며, 4) 간단한 수복 치료 외에 교정치료나 보철치료를 받지 않았으며, 특히 치아의 순면과 협면의 형태에 변형을 초래한 치과 치료를 받지 않았으며, 5) 단정한 안모를 가진 자를 선발 기준으로 정하여 선발하였다. 선정된 정상 교합자의 상, 하악 인상을 채득하고, 교정용 석고 모형을 제작하였다. 얻어진 치과 석고모형을 분석하여, Andrews의 Six keys to optimal occlusion에 부합되는 표본을 5 명의 숙련된 교정의사들이 선별하여 한국인 성인 정상교합자 치열의 석고 모형 155쌍(남자 92쌍,여자 63쌍)을 얻었다. 이들을 대상으로 정밀측정장비인 Coordinate Measuring Machine(CMM, MPC802, WEGU-Messtechnik, Germany)을 이용하여 3차원 digitization을 시행하고, 계측프로그램을 작성하여 SWA 제작을 위하여 필요한 Angulation, Inclination, In-and-Out, Molar offset angle, Arch-form 등을 측정하였다. 측정을 시행하기 전에, CMM을 이용한 3차 원 digitization의 오차에 대한 검증을 실시하였고, 3차원 digitization과 컴퓨터를 이용한 형태학적 분석법과 기존의 수작업에 의한 분석법의 신뢰도에 대한 분석을 실시하였다. 이상의 연구를 통하여 얻은 결론은 다음과 같다. 1. 치과 석고모형의 3차원 digitization에 CMM을 적용하여 mesh size 0.25 mm, 0.5 mm, 1.0 mm로 등간격 디지타이징하는 것은 모두 받아들일 수 있으며, 측정의 효율성을 고려할 때 1.0 mm간격으로 등간격 디지타이징 하는 것이 바람직하다. 2. 3차원 digitization과 컴퓨터를 이용한 방법이 Andrews의 방법에 기반한 수작업 방법보다 신뢰성이 높다. 3. 3차원 digitization과 컴퓨터를 이용한 방법으로 한국인의 치열의 형태학적 특성에 맞는 SWA의 제작을 위한 자료를 채득하였다.

• 치위생과학회지
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• 제9권1호
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• pp.99-108
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• 2009

본 연구는 교사의 구강보건교육 실천과 자기효능감이 구강보건에 대한 인식에 미치는 영향을 파악하기 위해 주요 관련 변인인 지식, 태도, 자기효능감, 실천의 관계에 대한 몇 가지 인과모형을 설정하였다. 서울시에 있는 특수학교 교사 376명을 대상으로 설문조사를 실시하였으며, 217명의 응답자 가운데 198명을 대상으로 t-검정, 일원배치분산분석, 상관분석, 경로분석을 하였다. 1. 교사의 성별, 연령, 경력에 따라 교사의 구강보건지식, 구강보건교육 교육에 대한 자기효능감, 구강보건교육에 대한 태도 수준을 비교한 결과, 교사의 성별에 따른 유의한 차이는 나타나지 않았으나, 교사의 연령에 따라 구강보건교육에 대한 자기효능감(p = 0.001)과 태도(p = 0.013)에 유의한 차이가 나타났다. 또한 교사의 경력에 따라 구강보건지식, 구강보건교육에 대한 자기효능감과 태도는 유의한 차이가 나타나지 않았다. 2. 교사의 구강보건지식, 구강보건교육에 대한 태도, 자기효능감, 구강보건교육 실천에 대한 상관관계를 분석하였다. 구강보건교육 태도, 자기효능감, 실천 사이에는 통계적으로 유의한 정(+)의 상관관계가 나타났으나, 교사의 구강보건 지식와 실천 사이에는 유의한 상관관계가 나타나지 않았다. 3. 교사의 구강보건 지식이 직접적으로 교사의 구강보건교육 실천에 직접적인 정(+)의 영향을 미치며, 교사의 구강보건교육에 대한 태도의 매개에 의해 교사의 구강보건교육 실천에 영향을 미치는 부분매개 모형(모형1)의 검증 결과, 지식과 태도 사이의 경로(Estimate=0.183, C.R.=0.294, p=0.003)와 태도와 실천 사이의 경로(Estimate=0.398, C.R. =3.090, p=0.002)는 통계적으로 유의하였으나, 지식과 실천 사이의 경로는 유의하지 않았다. 이 경로를 제외한 지식, 태도, 실천 사이의 완전매개 모형(모형1-1)은 모든 적합도 지수의 기준을 총족하였으나($x^2$=0.081, df=1, p=0.776, GFI=1.000, AGFI=0.998, NNFI= 1.178, NFI=0.996, CFI=1.000), 실천의 분산은 지식과 태도에 의해 충분히 설명되지 않았다(SMC=0.05). 4. 교사의 구강보건교육 실천이 구강보건교육에 대한 태도에 직접적인 정(+)의 영향을 미치며, 구강보건교육에 대한 자기효능감의 매개에 의해 교사의 구강보건교육 태도의 매개에 의해 영향을 미치는 부분매개 모형(모형2)의 검증 결과, 실천과 태도 사이의 경로(Estimate=0.273, C.R.=5.734, p<0.001)와 교사효능감과 태도 사이의 경로(Estimate=0.242, C.R.=4.426, p<0.001)는 통계적으로 유의하였으나, 실천과 태도 사이의 경로는 유의하지 않았다. 이 경로를 제외한 실천, 교사효능감, 태도 사이의 완전매개 모형(모형2-1)은 모든 적합도 기준을 충족하였으나($x^2$=2.081, df=1, p=0.149, GFI=0.993, AGFI=0.958, RMSEA=0.074, NNFI=0,942, NFI=0.965, CFI=0.981), 태도의 분산은 실천과 교사효능감에 의해 충분히 설명되지 않았다(0.136). 5. 지식태도실천 모형(모형2-1)에 교사의 구강보건교육에 대한 자기효능감을 매개변인으로 추가한 지식태도 자기효능감실천 모형(모형3)은 적합하게 나타났으며 ($x^2$=3.971, d.f.=3, p=0.271, RMSEA=0.039, GFI=0.990, AGFI=0.967, NNFI=0.971, NFI=0.944, CFI=0.986), 실천의 분산 중 14.3%가 지식, 태도, 자기효능감에 의해 설명되었다.

• Journal of Periodontal and Implant Science
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• 제52권6호
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• pp.479-495
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• 2022

Purpose: Rodent models have emerged as an alternative to established larger animal models for peri-implantitis research. However, the construct validity of rodent models is controversial due to a lack of consensus regarding their histological, morphological, and biochemical characteristics. This systematic review sought to validate rodent models by characterizing their morphological changes, particularly marginal bone loss (MBL), a hallmark of peri-implantitis. Methods: This review was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines. A literature search was performed electronically using MEDLINE (PubMed), and Embase, identifying pre-clinical studies reporting MBL after experimental peri-implantitis induction in rodents. Each study's risk of bias was assessed using the Systematic Review Center for Laboratory animal Experimentation (SYRCLE) risk of bias tool. A meta-analysis was performed for the difference in MBL, comparing healthy implants to those with experimental peri-implantitis. Results: Of the 1,014 unique records retrieved, 23 studies that met the eligibility criteria were included. Peri-implantitis was induced using 4 methods: ligatures, lipopolysaccharide, microbial infection, and titanium particles. Studies presented high to unclear risks of bias. During the osseointegration phase, 11.6% and 6.4%-11.3% of implants inserted in mice and rats, respectively, had failed to osseointegrate. Twelve studies were included in the meta-analysis of the linear MBL measured using micro-computed tomography. Following experimental peri-implantitis, the MBL was estimated to be 0.25 mm (95% confidence interval [CI], 0.14-0.36 mm) in mice and 0.26 mm (95% CI, 0.19-0.34 mm) in rats. The resulting peri-implant MBL was circumferential, consisting of supra- and infrabony components. Conclusions: Experimental peri-implantitis in rodent models results in circumferential MBL, with morphology consistent with the clinical presentation of peri-implantitis. While rodent models are promising, there is still a need to further characterize their healing potentials, standardize experiment protocols, and improve the reporting of results and methodology.

• The Journal of Advanced Prosthodontics
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• 제9권3호
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• pp.152-158
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• 2017

PURPOSE. The purpose of this study was to evaluate the influence of different coping thicknesses and veneer ceramic cooling rates on the failure load of zirconia-ceramic crowns. MATERIALS AND METHODS. Zirconia copings of two different thicknesses (0.5 mm or 1.5 mm; n=20 each) were fabricated from scanning 40 identical abutment models using a dental computer-aided design and computer-aided manufacturing system. Zirconia-ceramic crowns were completed by veneering feldspathic ceramics under different cooling rates (conventional or slow, n=20 each), resulting in 4 different groups (CONV05, SLOW05, CONV15, SLOW15; n=10 per group). Each crown was cemented on the abutment. 300,000 cycles of a 50-N load and thermocycling were applied on the crown, and then, a monotonic load was applied on each crown until failure. The mean failure loads were evaluated with two-way analysis of variance (P=.05). RESULTS. No cohesive or adhesive failure was observed after fatigue loading with thermocycling. Among the 4 groups, SLOW15 group (slow cooling and 1.5 mm chipping thickness) resulted in a significantly greater mean failure load than the other groups (P<.001). Coping fractures were only observed in SLOW15 group. CONCLUSION. The failure load of zirconia-ceramic crowns was significantly influenced by cooling rate as well as coping thickness. Under conventional cooling conditions, the mean failure load was not influenced by the coping thickness; however, under slow cooling conditions, the mean failure load was significantly influenced by the coping thickness.

• 대한치과교정학회지
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• 제21권1호
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• pp.223-238
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• 1991

This study was carried out in order to findout the amount of tooth movement, the changes arch size and the changes in arch morphology following orthodontic treatment and to provide a guideline for to predict post-treatment arch morphology. The sample group for this study consists of 15 males and 22 females, totalling in 37 persons, who received orthodontic treatment at Orthodontic Department of Dankook Univ. Dental Hospital. They are classified into Extraction Class I treatment group (E I), Non-extraction Class I treatment group (N I), and Non-extraction Class III treatment group (N III), according to their pre-treatment malocclusion state and methods of treatment. Following conclusions and averaged dental arch form for each group were obtained by cephalometric linear measurements and dental arch measurements using pre- and post-treatment lateral cephalograms and plaster study models. 1. Intercanine width were reduced in max. of both EI and NI during the period of treatment, 2. Intermolar width were reduced in max. of EI and increased in max. of NI. Therefore although there was no difference between these two groups before the treatment, intermolar width of the max, of NI was wider than that of E1 after the treatment. 3. PMV-incisor distance and PMV-canine distance were decreased in both max. and mand. of EI and that of NI, during the period of treatment. PMV-molar distance was decreased in both max. and mand. of NI and in mand. of NIII. 4. Items that showed stability during the treatment were: max. & mand. PMV-molar distance, mand. intercanine and intermolar width in EI; mand. intercanine and intermolar width in NI; mand. & max. PMV-incisor distance, PMV-canine distance, max. PMV-molar distance and max. & mand. intercanine and intermolar width in NIII. 5. The differences in averaged canine and molar variances to post-treatment dental arch form were present only in EI and in NI. There was no variance between maxilla and mandible in each group.

• 대한치과기공학회지
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• 제42권2호
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• pp.99-105
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• 2020

Purpose: A study analysed the stress distribution of abutment screw and supporting bone of fixture by the tightening torque force of the abutment screw within clinical treatment situation for the stability of the dental implant prosthesis. Methods: The finite element analysis was targeted to the mandibular molar crown model, and the implant was internal type 4.0 mm diameter, 10.0 mm length fixture and abutment screw and supporting bone. The occlusal surface was modeled in 4 cusps and loaded 100 N to the buccal cusps. The connection between the abutment and the fixture was achieved by combining three abutment tightening torque forces of 20, 25, and 30 Ncm. Results: The results showed that the maximum stress value of the supporting bone was found in the buccal cortical bone region of the fixture in all models. The von Mises stress value of each model showed 184.5 MPa at the 20 Ncm model, 195.3 MPa in the 25 Ncm model, and 216.5 MPa in the 30 Ncm model. The contact stress between the abutment and the abutment screw showed the stress value in the 20 Ncm model was 201.2 MPa, and the 245.5 MPa in the 25 Ncm model and 314.0 MPa in the 30 Ncm model. Conclusion: The increase of tightening force within the clinical range of the abutment screw of the implant dental prosthesis was found to have no problem with the stability of the supporting bone and the abutment screw.

• 대한치과기공학회지
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• 제39권1호
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• pp.25-33
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• 2017

Purpose: The aim of this study was to evaluate accuracy of glass fiber mesh complete denture of before and after curing. Methods: Edentulous model was selected as the master model. Ten study models were made by Type IV stone. Wax complete dentures were produced by the denture base and artificial teeth. CD and GD groups were measured six measurement distance before curing. The wax complete denture was investment after measurement is completed. Using a heat polymerization resin was injected resin. After injecting the resin it was curing. A complete denture was re-measured after curing. The measured data was verified by paired t-test. Results: Overall CD group was larger the value of the measured length. In the CD group, A-D point was larger. The smallest point was the B-D point. However, there was no statistically significant difference only C-D point(p>0.05). In the GD group, A-B point was larger. but B-D point was the smallest. A-D and B-C statistically points showed significant differences(p<0.05). Conclusion: Glass fiber mesh resin complete denture can be clinically applied to the edentulous patient.

• Imaging Science in Dentistry
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• 제42권3호
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• pp.163-167
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• 2012

Purpose: ANSI/ADA has established standards for adequate radiopacity. This study was aimed to assess the changes in radiopacity of composite resins according to various tube-target distances and exposure times. Materials and Methods: Five 1-mm thick samples of Filtek P60 and Clearfil composite resins were prepared and exposed with six tube-target distance/exposure time setups (i.e., 40 cm, 0.2 seconds; 30 cm, 0.2 seconds; 30 cm, 0.16 seconds, 30 cm, 0.12 seconds; 15 cm, 0.2 seconds; 15 cm, 0.12 seconds) performing at 70 kVp and 7 mA along with a 12-step aluminum stepwedge (1 mm incremental steps) using a PSP digital sensor. Thereafter, the radiopacities measured with Digora for Windows software 2.5 were converted to absorbencies (i.e., A=-log (1-G/255)), where A is the absorbency and G is the measured gray scale). Furthermore, the linear regression model of aluminum thickness and absorbency was developed and used to convert the radiopacity of dental materials to the equivalent aluminum thickness. In addition, all calculations were compared with those obtained from a modified 3-step stepwedge (i.e., using data for the 2nd, 5th, and 8th steps). Results: The radiopacities of the composite resins differed significantly with various setups (p<0.001) and between the materials (p<0.001). The best predicted model was obtained for the 30 cm 0.2 seconds setup ($R^2$=0.999). Data from the reduced modified stepwedge was remarkable and comparable with the 12-step stepwedge. Conclusion: Within the limits of the present study, our findings support that various setups might influence the radiopacity of dental materials on digital radiographs.

• Journal of Periodontal and Implant Science
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• 제48권1호
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• pp.12-21
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• 2018

Purpose: The goal of this study was to develop and validate a standardized in vitro pathogenic biofilm attached onto saliva-coated surfaces. Methods: Fusobacterium nucleatum (F. nucleatum) and Porphyromonas gingivalis (P. gingivalis) strains were grown under anaerobic conditions as single species and in dual-species cultures. Initially, the bacterial biomass was evaluated at 24 and 48 hours to determine the optimal timing for the adhesion phase onto saliva-coated polystyrene surfaces. Thereafter, biofilm development was assessed over time by crystal violet staining and scanning electron microscopy. Results: The data showed no significant difference in the overall biomass after 48 hours for P. gingivalis in single- and dual-species conditions. After adhesion, P. gingivalis in single- and dual-species biofilms accumulated a substantially higher biomass after 7 days of incubation than after 3 days, but no significant difference was found between 5 and 7 days. Although the biomass of the F. nucleatum biofilm was higher at 3 days, no difference was found at 3, 5, or 7 days of incubation. Conclusions: Polystyrene substrates from well plates work as a standard surface and provide reproducible results for in vitro biofilm models. Our biofilm model could serve as a reference point for studies investigating biofilms on different surfaces.