• The Journal of Advanced Prosthodontics
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• 제5권3호
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• pp.219-225
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• 2013

PURPOSE. Few studies have investigated the marginal accuracy of 3-unit zirconia fixed partial dentures (FPDs) fabricated by computer-aided design/computer-aided manufacturing (CAD/CAM) system. The purpose of this study was to compare the marginal fit of zirconia FPDs made using two CAD/CAM systems with that of metal-ceramic FPDs. MATERIALS AND METHODS. Artificial resin maxillary central and lateral incisors were prepared for 3-unit FPDs and fixed in yellow stone. This model was duplicated to epoxy resin die. On the resin die, 15 three-unit FPDs were fabricated per group (45 in total): Group A, zirconia 3-unit FPDs made with the Everest system; Group B, zirconia 3-unit FPDs made with the Lava system; and Group C, metal-ceramic 3-unit FPDs. They were cemented to resin dies with resin cement. After removal of pontic, each retainer was separated and observed under a microscope (Presize 440C). Marginal gaps of experimental groups were analyzed using one-way ANOVA and Duncan test. RESULTS. Mean marginal gaps of 3-unit FPDs were $60.46{\mu}m$ for the Everest group, $78.71{\mu}m$ for the Lava group, and $81.32{\mu}m$ for the metal-ceramic group. The Everest group demonstrated significantly smaller marginal gap than the Lava and the metal-ceramic groups (P<.05). The marginal gap did not significantly differ between the Lava and the metal-ceramic groups (P>.05). CONCLUSION. The marginal gaps of anterior 3-unit zirconia FPD differed according to CAD/CAM systems, but still fell within clinically acceptable ranges compared with conventional metal-ceramic restoration.

• 대한치과기공학회지
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• 제34권4호
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• pp.353-359
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• 2012

Purpose: The aim of this study measured and compared the marginal and internal fit of metal cores with two base metal alloy (Ni-Cr alloy(non-beryllium), Co-Cr alloy). Methods: Maxillary right first molar abutment fabricated by titanium was prepared for this study. Impressions(10ea) were made from titanium model, and study models were poured with improved dental stone. Wax cores of twenty were prepared for burn-out and casting. Ten wax cores cast Ni-Cr alloy(non-Be), and finally ten cast Co-Cr alloy. Marginal and internal fit of cores was evaluated using silicone replica technique and digital microscope(x160). The data were statistically analyzed with the independent samples t-test (${\alpha}$ <.05). Results: Mean(standard deviation, SD) marginal and internal fit total size of Ni-Cr alloy(non-Be) group was $73.3(14.4){\mu}m$ and of Co-Cr alloy group $65.6(17.4){\mu}m$. The marginal and internal fit total size of Ni-Cr alloy group(non-Be) was statistically significantly greater than that of Co-Cr alloy group (P=.004). Conclusion: Co-Cr alloy cores in this study had a better marginal fit than Ni-Cr alloy(non-Be) cores.

• 대한치과보철학회지
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• 제37권4호
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• pp.506-515
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• 1999

Dental practice can produce and spread some infectious diseases from patients to dentist, dental assistant, and dental labors. One possible method for preventing these cross-contamination is to immerse dental impression in chemical disinfectants. So for many investigators studied on the dimensional changes of dental impressions and on the surface qualities of stone casts made from impression following immersion in disinfectants. This study was proposed to evaluate some popular impression disinfectant combination from the point of dimensional stability. Impression was taken from dental arch-shaped metal model. Irreversible hydrocolloid and 3 elastomers(polyvinyl siloxane, polysulfide, polyether) were immersed in 3 disinfectants (2% glutaraldehyde, 1% povidone-iodine, 0.5% sodium hypochlorite) for 10 minutes and measured both cross-arch and anterior-posterior distance under stereo microscope to evaluate dimensional change. The results obtained were as follows: 1. Dimensional changes of irreversible hydrocolloid impression was statistically different in cross-arch and anterior-posterior distance when immersed in 2% glutaraldehyde solution and in anterior-posterior distance when immersed in 0.5% sodium hypochlorite solution from control group (p<0.05). 2. Dimensional changes of polyvinyl siloxane and polysulfide impression were not statistically different from control group (p>0.05). 3. Dimensional changes of polyether impression was statistically different in cross-arch distance when immersed in 0.5% sodium hypochlorite solution and in anterior-posterior distance when immersed in 1% povidone-iodine solution from control group (p<0.05). 4. In all cases, dimensional changes were less than 0.1% from the original dimension and concluded clinically acceptable.

• The Journal of Advanced Prosthodontics
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• 제5권2호
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• pp.179-186
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• 2013

PURPOSE. One of the most important factors in evaluating the quality of fixed dental prostheses (FDPs) is their gap. The purpose of this study was to compare the marginal and internal gap of two different metal-ceramic crowns, casting and selective laser sintering (SLS), before and after porcelain firing. Furthermore, this study evaluated whether metal-ceramic crowns made using the SLS have the same clinical acceptability as crowns made by the traditional casting. MATERIALS AND METHODS. The 10 study models were produced using stone. The 20 specimens were produced using the casting and the SLS methods; 10 samples were made in each group. After the core gap measurements, 10 metal-ceramic crowns in each group were finished using the conventional technique of firing porcelain. The gap of the metal-ceramic crowns was measured. The marginal and internal gaps were measured by two-dimensional and three-dimensional replica techniques, respectively. The Wilcoxon signed-rank test, the Wilcoxon rank-sum test and nonparametric ANCOVA were used for statistical analysis (${\alpha}$=.05). RESULTS. In both groups, the gap increased after completion of the metal-ceramic crown compared to the core. In all measured areas, the gap of the metal cores and metal-ceramic crowns produced by the SLS was greater than that of the metal cores and metal-ceramic crowns produced using the casting. Statistically significant differences were found between cast and SLS (metal cores and metal-ceramic crown). CONCLUSION. Although the gap of the FDPs produced by the SLS was greater than that of the FDPs produced by the conventional casting in all measured areas, none exceeded the clinically acceptable range.

• 구강회복응용과학지
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• 제36권4호
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• pp.242-253
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• 2020

목적: 이 연구의 목적은 3D 프린팅으로 제작된 다이의 정확도를 인상재와 치과용 석고를 이용하여 제작한 기존 방식 다이와 비교하고 체적 변화를 평가하여 정확도를 비교하는 것이다. 연구 재료 및 방법: 치과용 모델 하악 우측 제1대구치를 준비하여 스캔한 뒤 polyetherketoneketone (PEKK)으로 기준 다이를 제작한다. 기존 방식 다이는 기준 다이를 polyvinylsiloxane로 인상채득한 뒤 Type IV 치과용 석고를 부었다. 3D 프린팅 시스템의 경우 기준 다이를 스캔하고 3개의 서로 다른 3D 프린터를 이용하여 모델로 변환하였다. 4가지 방법으로 각각 10개의 표본을 만들었다. 3D 표면매칭 소프트웨어를 사용하여 기준 다이와 중첩하였다. 통계 분석을 위해 Kruskal-Wallis test, Mann-Whitney U test를 수행하였다(P < 0.05). 결과: 기준 다이와 비교하여 기존 방식, Stereolithography로 제작된 다이를 제외하고는 각 방식으로 제작된 다이의 체적 변화가 상당히 있었다(P < 0.05). 기존 방식으로 제작된 다이는 3D 프린팅된 다이보다 체적 변화가 가장 적었다(P < 0.05). Stereolithography로 제작된 3D 프린팅 다이는 다른 3D 프린터 중에서 체적 변화가 가장 적었다(P < 0.05). 결론: 기존 방식의 다이는 3D 프린팅 다이보다 더 정확했지만 3D 프린팅 다이는 임상적으로 허용되는 범위 내에 있었다. 따라서 3D 프린팅 다이는 수복물 제작에 사용할 수 있다.

• 구강회복응용과학지
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• 제23권3호
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• pp.239-248
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• 2007

The accuracy and dimensional stability of rubber impression materials are very important for the fitness of the final restoration. The purpose of this investigation was to evaluate the effects of the storage time and pouring frequency of the additional silicone materials on dimensional stability. Total 30 impressions were made of tooth prepared single crown. The dies had 1 buccolingual, 1 mesiodistal and 1 occlusogingival lines. Two additional silicone materials(examixfine, aquasil) were included. 15 specimens were made of each impression material and poured by type IV stone over times(1hour, 24hours, 72hours) after mixing. 5 impressions poured after 1 hour were used for second pouring after 24hours and third pouring after 72hours. The same examiner measured each specimen 3 times after lazer scanning. All statistical tests were performed with the level of significance set at 0.05. The results indicated that significant difference at any measuring point of stone dies except the buccolingual and mesiodistal lines of the specimen made at 1hour after mixing with examixfine when measurements at 1hour, 24hours and 72hours were campared. There were significant difference between two impression materials and at every measuring point of stone dies made at second and third pouring. The length of measuring point increased significantly as time passed by and increase of the pouring frequency. However, this results are clinically acceptable except the dies of the third pouring. Under the conditions of this study, the shrinkage rate of the additional silicone rubber impression materials significantly increased as time passed by and increase of the pouring frequency.

• 대한치과보철학회지
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• 제30권1호
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• pp.1-14
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• 1992

The purpose of this study was to evaluate the accuracy of reproduction of stone casts made from complete-arch impressions using different trays. The trays used were : 1) nonperforated custom tray, 2) perforated custom tray, 3) nonperforated Rim-Lock tray, 4) perforated stock tray. Impressions were made from an dentulous acrylic resin model with metal inserts in first premolars and second molars. Transverse distance, sagittal distance and diagonal distance were measured using 4 landmarks. Measurements were made by using 3 dimensional measuring machine. The impression material used was an addition silicone. Impressions were poured at once with a Type IV dental stone. Data were analyzed using ANOVA and student t-test with a sample size of five. The results were as follows : 1. There were statistical differences in amount of dimensional change in according to the tray types. In amount of mean dimensional change, perforated custom tray was the first smallest, nonperforated custom tray was the second, nonperforated Rim-Lock tray and perforated stock tray were the largest. 2. There were statistical differences in amount of dimensional change between nonperforated custom tray and nonperforated Rim-Lock tray, and between perforated custom tray perforated stock tray. 3. There were satistical differences in amount of dimensional change between nonperforated custom tray and perforated custom tray, but there was not a statistical difference between nonperforated Rim-Lock tray and perforated stock tray. 4. There was not a statistical difference in amount of dimensional change between upper and lower arch in all tray types.

• 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.

• 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.

• 대한치과기공학회지
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• 제41권4호
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• pp.263-269
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• 2019

Purpose: The purpose of this study was to evaluate the internal fitness of prostheses fabricated with non-contact extra-oral scanner and those fabricated with intra-oral video scanner, with a comparative accuracy analyses of their precision and trueness. Methods: A polymethyl methacrylate (PMMA) model was fabricated by replicating a master model. The prostheses in the first group were fabricated based on the PMMA model with an intra-oral video scanner (IVS group). Following the fabrication of work models with Type IV Stone that were based on the PMMA model, the prostheses in the second group were fabricated with a non-contact extra-oral scanner (ENB group). The precision and trueness of the prostheses were calculated from comparisons of the three-dimensional images of the internal surfaces of the prostheses and those of the master model. Kruskal-Wallis tests were used to determine the statistical significance, with the level of type 1 error set at 0.05. Results: Trueness (P < 0.009) and precision (P < 0.001) did not differ significantly between the ENB and IVS groups. The IVS group exhibited lower trueness values and larger precision values than the ENB group. Conclusion: Although no significant differences were found in the internal fitness of the prostheses that were fabricated by the two different scanners, the intraoral video scanner-fabricated prostheses had better trueness, whereas the non-contact extra-oral scanner-fabricated prostheses had better precision.