• 대한치과기공학회지
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• 제44권1호
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• pp.1-7
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• 2022

Purpose: The purpose of this in vitro study is to evaluate the clinical acceptability of the marginal discrepancies and internal spacing of multi-layered zirconia prothesis by speed sintering. Methods: The two specimen types come from the same manufacturer but differ in the ingredients in layered zirconia and indication, that is anterior and posterior. The designs of both specimens were full contour crowns, and a total of 20 pieces were repeatedly fabricated, 10 for each group. The specimens were divided into two subgroups (n=10) and sintered with various total times (4 hours, 8 hours) at the maximum temperature (1,530℃). The gap between the two groups of multi-layered zirconia prostheses was measured using a silicone replica technique of 2D analysis method. The independent sample t-test was then used to compare and analyze the data obtained from the two groups (α=0.05). Results: The marginal and internal gap was superior in the 8-hour compared to the 4-hour group, and the results exhibited significant differences (p<0.05). All specimens showed that using the speed sintering schedule does not exceed the clinically permitted value of 120 ㎛, meaning zirconia prothesis using the speed sintering was adequate. Conclusion: The sintering condition is shown to affect the marginal and internal gaps of multi-layered zirconia restoration.

• 대한치과기공학회지
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• 제38권4호
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• pp.305-311
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• 2016

Purpose: The purpose of this study were to analysis of marginal adaptation of metal cores fabricated by selective laser sintering. Methods: Main model was prepared and ten stone models were fabricated. Ten single metal cores were fabricated by selective laser sintering(SLS group) and another ten single metal cores using lost wax technique and casting method were manufactured(CAST group). The marginal adaptation of metal cores were analysis using by the silicone replica technique. Silicone replicas were sectioned two times. The marginal adaptations were measured using by digital microscope. Statistical analyses was performed with independent t-test(${\bullet}{\cdot}=0.05$). Results: Means of marginal adaptations were 90.3 ${\ss}{\uparrow}$ for SLS group and 65.1 ${\ss}{\uparrow}$ for CAST group. Two groups were statistically significant differences (p < 0.05). Conclusion: Marginal adaptation of metal cores fabricated by selective laser sintering were ranged within the clinical recommendation.

• 대한치과기공학회지
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• 제41권1호
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• pp.1-7
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• 2019

Purpose: The objectives of this study was to evaluate clinical adaptation of dental prostheses printed by 3 dimensional(3D) printing technology. Methods: Ten study models were prepared. Ten specimens of experimental group were printed by 3D printing(3DP group). As a control group, 10 specimens were fabricated by casting method on the same models. Marginal gaps of all specimens were measured to evaluate clinical adaptation. Marginal adaptations were measured using silicone replica technique and measured at 8 sites per specimen. Wilcoxon's signed-ranks test was used for statistical analysis(${\alpha}=0.05$). Results: Means of marginal adaptations were $95.1{\mu}m$ for 3DP group and $75.9{\mu}m$ for CAST group(p < 0.000). Conclusion : However, the mean of the 3DP group was within the clinical tolerance suggested by the previous researchers. Based on this, dental prosthesis fabricated by 3D printing technology is considered to be clinically acceptable.

• 구강회복응용과학지
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• 제33권2호
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• pp.63-70
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• 2017

임상적으로 고정성보철물의 적합도는 성공적인 수복을 위해 필수적인 요소이다. 보철물의 적합도는 크게 변연적합도와 내면적합도로 분류되며, 이를 평가하기 위한 방법으로는 현미경 변연 측정법, 절단면 측정법, 실리콘 복제법, 3차원 스캔데이터 중첩법, 무게 측정법, 마이크로 CT 측정법 등 다양한 방법들이 소개되고 있다. 이에 본 연구에서는 기존의 문헌들을 바탕으로 각 방법들의 장, 단점을 비교분석함으로써 디지털환경에서 보다 편리하고 정확한 측정법을 제시하고자 한다.

• The Journal of Advanced Prosthodontics
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• 제12권2호
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• pp.100-106
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• 2020

PURPOSE. The purpose of this in vitro study was to evaluate the fitting accuracy of single crowns made from a novel presintered Co-Cr alloy prepared with a computer-aided design and computer-aided manufacturing (CAD/CAM) technique, as compared with crowns manufactured by other digital and the conventional casting technique. Additionally, the influence of oxide layer on the fitting accuracy of specimens was tested. MATERIALS AND METHODS. A total of 40 test specimens made from Co-Cr alloy were investigated according to the fitting accuracy using a replica technique. Four different methods processing different materials were used for the manufacture of the crown copings (milling of presintered (Ceramill Sintron-group_cer_sin) or rigid alloy (Tizian NEM-group_ti_nem), selective laser melting (Ceramill NPL-group_cer_npl), and casting (Girobond NB-group_gir_nb)). The specimens were adapted to a resin model and the outer surfaces were airborne-particle abraded with aluminum oxide. After the veneering process, the fitting accuracy (absolute marginal discrepancy and internal gap) was evaluated by the replica technique in 2 steps, before removing the oxide layer from the intaglio surface of the crowns, and after removing the layer with aluminum oxide airborne-particle abrasion. Statistical analysis was performed by multifactorial analysis of variance (ANOVA) (α=.05). RESULTS. Mean absolute marginal discrepancy ranged between 20 ㎛ (group_cer_npl for specimens of Ceramill NPL) and 43 ㎛ (group_cer_sin for crowns of Ceramill Sintron) with the oxide layer and between 19 ㎛ and 28 ㎛ without the oxide layer. The internal gap varied between 33 ㎛ (group_ti_nem for test samples of Tizian NEM) and 75 ㎛ (group_gir_nb for the base material Girobond NB) with the oxide layer and between 30 ㎛ and 76 ㎛ without the oxide layer. The absolute marginal discrepancy and the internal gap were significantly influenced by the fabrication method used (P<.05). CONCLUSION. Different manufacturing techniques had a significant influence on the fitting accuracy of single crowns made from Co-Cr alloys. However, all tested crowns showed a clinically acceptable absolute marginal discrepancy and internal gap with and without oxide layer and could be recommended under clinical considerations. Especially, the new system Ceramill Sintron showed acceptable values of fitting accuracy so it can be suggested in routine clinical work.

• 대한치과기공학회지
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• 제46권1호
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• pp.1-7
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• 2024

Purpose: The goal of this study was to determine the clinical acceptability of various cement space settings for the marginal and internal fit of a zirconia core manufactured using additive manufacturing. Methods: The maxillary right incisor served as the master model. After scanning the maxillary right incisor with a dental 3D (three-dimensional) scanner, the stereo lithography file was created using different cement space settings of 40, 120, and 200 ㎛ using computer-aided design software (Dental System 2018; 3Shape). The marginal and internal fit of the 3 groups were determined using the silicon replica technique. Measurement points were divided into the following three categories: margin, axial wall, and incisal. To ensure more accurate measurements, these three measurement points were divided into 8 points. The Shapiro-Wilk, one-way ANOVA, and Tukey's honestly significant difference test (for all tests α=0.05) were the statistical analyses that were included in the study. Results: The CS (cement space)-200 group had better marginal and internal fit than the CS-40 and CS-120 groups, and there were statistically significant differences at the marginal and incisal points, except for the axial wall points. CS-200 group, both marginal and internal fit were within 120 ㎛, which is the clinically acceptable value. Conclusion: This study suggests that a 200 ㎛ cement space setting is ideal for optimal marginal and internal fit of 3D-printed ceramic crowns.

• The Journal of Advanced Prosthodontics
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• 제7권4호
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• pp.294-302
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• 2015

PURPOSE. The purpose of this study was to verify the clinical-feasibility of additive manufacturing by comparing the accuracy of four different manufacturing methods for metal coping: the conventional lost wax technique (CLWT); subtractive methods with wax blank milling (WBM); and two additive methods, multi jet modeling (MJM), and micro-stereolithography (Micro-SLA). MATERIALS AND METHODS. Thirty study models were created using an acrylic model with the maxillary upper right canine, first premolar, and first molar teeth. Based on the scan files from a non-contact blue light scanner (Identica; Medit Co. Ltd., Seoul, Korea), thirty cores were produced using the WBM, MJM, and Micro-SLA methods, respectively, and another thirty frameworks were produced using the CLWT method. To measure the marginal and internal gap, the silicone replica method was adopted, and the silicone images obtained were evaluated using a digital microscope (KH-7700; Hirox, Tokyo, Japan) at 140X magnification. Analyses were performed using two-way analysis of variance (ANOVA) and Tukey post hoc test (${\alpha}=.05$). RESULTS. The mean marginal gaps and internal gaps showed significant differences according to tooth type (P<.001 and P<.001, respectively) and manufacturing method (P<.037 and P<.001, respectively). Micro-SLA did not show any significant difference from CLWT regarding mean marginal gap compared to the WBM and MJM methods. CONCLUSION. The mean values of gaps resulting from the four different manufacturing methods were within a clinically allowable range, and, thus, the clinical use of additive manufacturing methods is acceptable as an alternative to the traditional lost wax-technique and subtractive manufacturing.

• 치위생과학회지
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• 제15권2호
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• pp.196-201
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• 2015

본 연구에서는 최근 창조경제의 일환으로서 3차원 프린팅 기술의 개발이 눈에 띄게 발전함에 따라 치의학계 보철물 제작 기술에도 영향을 주고 있는 이 기술에 의해 제작된 3본 고정성 보철물의 임상적 허용 가능성을 변연 간격을 기준으로 가늠하여보고자 하였다. 3차원 프린팅 기술에 의해 제작된 보철물 평가와 관련한 연구가 부족함에 따라 본 연구 결과를 통해 해당 종사자들(치과의사, 치과위생과, 치과기공사)에게 참고자료를 제시하고자 하였다. 연구 결과들을 종합하여 보면 3차원 프린팅 기술에 의해 제작된 3본 고정성 보철물은 같은 증례를 대상으로 전통적인 제작방식에 의해 제작된 것보다 변연 간격이 우수하지 못하였다. 비록 몇몇 임상가들이 제시한 임상적 허용 수치 내에는 존재하였으나 기존의 제작 기술을 대신하기 위해서는 앞으로 많은 연구들을 통하여 기술의 발전이 이루어져야 할 것으로 생각된다.

• The Journal of Advanced Prosthodontics
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• 제9권6호
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• pp.463-469
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• 2017

PURPOSE. To evaluate the fit of a three-unit metal framework of fixed dental prostheses made by subtractive and additive manufacturing. MATERIALS AND METHODS. One master model of metal was fabricated. Twenty silicone impressions were made on the master die, working die of 10 poured with Type 4 stone, and working die of 10 made of scannable stone. Ten three-unit wax frameworks were fabricated by wax-up from Type IV working die. Stereolithography files of 10 three-unit frameworks were obtained using a model scanner and three-dimensional design software on a scannable working die. The three-unit wax framework was fabricated using subtractive manufacturing (SM) by applying the prepared stereolithography file, and the resin framework was fabricated by additive manufacturing (AM); both used metal alloy castings for metal frameworks. Marginal and internal gap were measured using silicone replica technique and digital microscope. Measurement data were analyzed by Kruskal-Wallis H test and Mann-Whitney U-test (${\alpha}=.05$). RESULTS. The lowest and highest gaps between premolar and molar margins were in the SM group and the AM group, respectively. There was a statistically significant difference in the marginal gap among the 3 groups (P<.001). In the marginal area where pontic was present, the largest gap was $149.39{\pm}42.30{\mu}m$ in the AM group, and the lowest gap was $24.40{\pm}11.92{\mu}m$ in the SM group. CONCLUSION. Three-unit metal frameworks made by subtractive manufacturing are clinically applicable. However, additive manufacturing requires more research to be applied clinically.

• The Journal of Advanced Prosthodontics
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• 제9권4호
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• pp.239-243
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• 2017

PURPOSE. The purpose of this study is to compare single and three-unit metal frameworks that are produced by micro-stereolithography. MATERIALS AND METHODS. Silicone impressions of a selected molar and a premolar were used to make master abutments that were scanned into a stereolithography file. The file was processed with computer aided design software to create single and three-unit designs from which resin frameworks were created using micro-stereolithography. These resin frameworks were subjected to investment, burnout, and casting to fabricate single and three-unit metal ones that were measured under a digital microscope by using the silicone replica technique. The measurements were verified by means of the Mann-Whitney U test (${\alpha}=.05$). RESULTS. The marginal gap was $101.9{\pm}53.4{\mu}m$ for SM group and $104.3{\pm}62.9{\mu}m$ for TUM group. The measurement of non-pontics in a single metal framework was $93.6{\pm}43.9{\mu}m$, and that of non-pontics in a three-unit metal framework was $64.9{\pm}46.5{\mu}m$. The dimension of pontics in a single metal framework was $110.2{\pm}61.4{\mu}m$, and that of pontics in a three-unit metal framework was $143.7{\pm}51.8{\mu}m$. CONCLUSION. The marginal gap was smaller for the single metal framework than for the three-unit one, which requires further improvement before it can be used for clinical purposes.