• 대한치과보철학회지
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• 제36권1호
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• pp.120-132
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• 1998

This stusy was to investigate the marginal fitness of porcelain-fused-to- metal crown after succesive firing cycle. Main variables were the degree of marginal curvature of labiocervical margin and the type of alloy. The exaggerated marginal curvature(EMC) was created by additional reduction at the faciocervical wall of the normallized marginal curvature (NMC)-typed ivorine tooth by using milling machine. The difference in the shape was the mid facial margin was placed 2mm apical to cemento- enamel junction in labial surface. Three types of alloy were high noble, noble, and base metal alloy. Test specimens were divided into 8 groups and each group had 8 specimens. Sixty four ceramometal crowns were made totally. Measurement stages were following degassing, opaquing. body porcelain firing, and glazing, and measuring sites were 4. (midmesial, midfacial, middistal, and midlingual). Digital, travelling measuring microscope (0.5 um precision, Olympus. Japan) was used under ${\times}250$ magnification. Within the limitation of this investigation, it was concluded as belows: 1. The pattern of marginal distortion was varied. Degassing stage was not a specific, causative stage that induce most of total marginal distortion during whole procedure fabricating a ceramometal crown. Body firing stage induced discrepancy relatively more than other firing stages. 2. The specimens that were Ni-based alloy and had EMC were distorted persistently following successive fabricating procedures. But marginal openings were decreased after glazing. 3. The release of metal grinding-induced stress was presumed as a cause that induce marginal distortion. 4. The amount of discrepancies of the labial and lingual margins were greater than that of the mesial and distal margin in the specimen that had EMC. 5. Silver-plated die was not enough to resist abrasion during repeated seating of metal copings on the die-holding device.

• 대한치과보철학회지
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• 제38권6호
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• pp.791-799
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• 2000

Statement of problem. Targis/Vectris restorations provide excellent esthetics. Marginal accuracy is significantly influenced by the preparation design. There were no studies to examine the effect of preparation design on the marginal discrepancy and fracture strength of Targis / Vectris crowns. Purpose. This study evaluated the marginal accuracy before and after cementation, and the fracture strength of FRC/Ceromer(Targis / Vectris) crowns according to different preparation design. Material and method. Three metal dies with different convergence angles($6^{\circ},\;10^{\circ},\;15^{\circ}$) were prepared. Total 30 (10 for each angle) Targis/Vectris crowns were made. The restorations were evaluated for adaptation of the margin before and after cementation, then were compressively loaded to failure. Fracture surfaces of the crowns were examined using a SEM. Results. The mean marginal gap was $49{\yen}m\;for6^{\circ},\;55{\S}>for\;10^{\circ}\;and\;70{\S}>for\;15^{\circ}$ and in clinically acceptable level. The mean marginal gap increased significantly after cementation. The increasing amount during cementation was the largest in the $6^{\circ}$ group. The crowns on 60 convergence angle had a significantly higher fracture strength than the crowns on $15^{\circ}$ angle. Mean fracture strength of total crowns regardless of convergence angle was 1390 N, which was higher than all-ceramic crowns. SEM observation showed two-mode fracture pattern. Conclusion. From the results of this study, all of the FRC/Ceromer crowns had clinically acceptable marginal accuracy and could withstand the bite force. Moreover, less convergent angle than all-ceramic crown might be recommended for preparation procedure.

• The Journal of Advanced Prosthodontics
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• 제14권4호
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• pp.250-261
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• 2022

PURPOSE. The purpose of this study was to analyze the marginal fit of three-unit resin prostheses printed with the stereolithography (SLA) method in two build orientations (45°, 60°) and two layer thicknesses (50 ㎛, 100 ㎛). MATERIALS AND METHODS. A master model for a three-unit resin prosthesis was designed with two implant abutments. Forty specimens were printed using an SLA 3D printer. The specimens were printed with two build orientations (45°, 60°), and each orientation was printed with two layer thicknesses (50 ㎛, 100 ㎛). The marginal fit was measured as the marginal gap (MG) and absolute marginal discrepancy (AMD), and MG and AMD measurements were performed at 8 points per abutment, for 16 points per specimen. All statistical analyses were performed using SPSS software. Two-way analysis of variance (ANOVA) was separately performed on the MG and AMD values of the build orientations and layer thicknesses. Moreover, one-way ANOVA was performed for each point within each group. RESULTS. The margins of the area adjacent to the pontic showed significantly high values, and the values were smaller when the build orientation was 45° than when it was 60°. However, the margin did not differ significantly according to the layer thicknesses. CONCLUSION. The marginal fit of the three-unit resin prosthesis fabricated by the SLA 3D method was affected by the pontic. Moreover, the marginal fit was affected by the build orientation. The 45° build orientation is recommended.

• 대한치과보철학회지
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• 제54권3호
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• pp.210-217
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• 2016

목적: 본 연구의 목적은 실제 환자에서 디지털 구강스캐너로 모형 없이 제작한 보철물의 변연 및 내면 적합도를 평가하는 것이다. 대상 및 방법: 전향적 임상시험으로 시행한 본 예비 연구는 총 11개의 수복물을 대상으로 하였다. 구강스캐너(TRIOS, 3shape, Copenhagen, Denmark)로 디지털 구강인상을 채득한 후, 캐드 디자인 및 밀링 가공 과정을 통해 전부지르코니아 수복물을 제작하였다. 완성된 지르코니아관을 환자 구강 내에 시적하였고, 레플리카 술식으로 보철물-지대치 복제물을 얻었다. 이를 근원심, 협설 방향으로 잘라 변연오차, 변연간극과 축벽부, 선각부, 교합면부의 내면간극을 측정하였다. 통계처리는 Kruskal-Wallis 검정과 Mann-Whitney U 검정을 이용하여 통계적 유의성을 분석하였다(${\alpha}=.05$). 결과: 복제물을 통한 적합도 분석 결과, 근원심, 협설 절편 사이에는 통계적으로 유의한 차이가 없었다(P>.05). 변연간극에 불일치가 있었으며, 변연 오차가 변연간극 보다 컸다(P<.01). 결론: 본 연구의 한계 내에서, 구강스캐너로 모형 없이 제작한 전부지르코니아 수복물의 적합도는 임상적으로 허용할만한 결과를 보였다. 그러나 지르코니아관의 변연부위가 과풍융되는 경향이 있었으므로 주의 깊은 임상 적용 및 추적 연구가 요구된다.

• 구강회복응용과학지
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• 제29권4호
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• pp.366-376
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• 2013

구강내 스캔(Group 1), 모델 광학 스캔(Group 2)과 모델 접촉식 스캔(Group 3)방식으로 각각 zirconia 코핑을 제작하여 광학 현미경으로 적합성을 관찰하였다. 측정항목은 변연오차(absolute marginal discrepancy;AMD), 변연간극(marginal gap; MG), 측방간격(gap of axial wall; GA), 선각간격(gap of line angle; GL)와 교합간격(gap of occusal surface; GO)이었으며, 결과는 아래와 같았다. 1. Group 1, Group 2, Group 3의 평균 AMD는 각 각 $141.21{\pm}42.94{\mu}m$, $140.63{\pm}31.64{\mu}m$, $109.37{\pm}28.42{\mu}m$이고, Group1, Group 2, Group 3의 MG는 각 각 $82.52{\pm}43.99{\mu}m$, $90.28{\pm}27.93{\mu}m$, $66.55{\pm}28.77{\mu}m$였다. AMD와 MG는 각 그룹에서 통계학적으로 유의한 차이를 보여주지 않았다(Anova test, P>0.05). 2. Group 2의 GA가 Group 1과 Group 3에 비해 통계학적으로 유의하게 적은 수치를 나타내었다(Anova test, P<0.05). 3. Group 1의 GL과 GO가 다른 그룹에 비해 통계학적으로 높은 수치를 나타내었다(Mann-whitney test(P<0.05). 세 가지 스캔 방식으로 제작된 zirconia 코핑은 세라믹 보철의 가장 중요한 평가 요소인 AMD와 MG에서 서로 통계학적 차이를 보이지 않았다.

• The Journal of Advanced Prosthodontics
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• 제15권3호
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• pp.155-170
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• 2023

PURPOSE. This study aims to clinically compare the fitness and trueness of zirconia crowns fabricated by different combinations of open CAD-CAM systems. MATERIALS AND METHODS. Total of 40 patients were enrolled in this study, and 9 different zirconia crowns were prepared per patient. Each crown was made through the cross-application of 3 different design software (EZIS VR, 3Shape Dental System, Exocad) with 3 different processing devices (Aegis HM, Trione Z, Motion 2). The marginal gap, absolute marginal discrepancy, internal gap(axial, line angle, occlusal) by a silicone replica technique were measured to compare the fit of the crown. The scanned inner and outer surfaces of the crowns were compared to CAD data using 3D metrology software to evaluate trueness. RESULTS. There were significant differences in the marginal gap, absolute marginal discrepancy, axial and line angle internal gap among the groups (P < .05) in the comparison of fit. There was no statistically significant difference among the groups in terms of occlusal internal gap. The trueness ranged from 36.19 to 43.78 ㎛ but there was no statistically significant difference within the groups (P > .05). CONCLUSION. All 9 groups showed clinically acceptable level of marginal gaps ranging from 74.26 to 112.20 ㎛ in terms of fit comparison. In the comparison of trueness, no significant difference within each group was spotted. Within the limitation of this study, open CAD-CAM systems used in this study can be assembled properly to fabricate zirconia crown.

• 무역학회지
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• 제47권2호
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• pp.31-46
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• 2022

The purpose of this study is to measure the degree of discrepancies in the bilateral trade data between South Korea and its five major trade partners and to identify the key factors causing the discrepancies. By analyzing statistics based on the CIF/FOB ratio estimation and taking into consideration the trade flow via Hong Kong, the study finds that the discrepancies in South Korea's trade data with the US, Vietnam, and Japan are insignificant. In case of Hong Kong, however, the value of South Korea's import from Hong Kong is extensively inconsistent with Hong Kong's export to South Korea(i.e. the mirror data) while the value of South Korea's export to Hong Kong generally corresponds to its mirror data. Such discrepancies are caused by differences in recording re-exports, which are often found in the trade flow via entrepôt economics including Hong Kong. Meanwhile, discrepancies in reported bilateral trade flows between South Korea and People's Republic of China(PRC) remain relatively marginal. The discrepancy of statistics between South Korea as the exporter and PRC as the importer is mainly caused by the trade flow via Hong Kong. On the other hand, the discrepancy of statistics between South Korea as the importer and PRC as the exporter is assumably due to the differences in attribution of trade partners.

• 대한치과보철학회지
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• 제20권1호
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• pp.75-81
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• 1982

The purpose of this study was to compare the marginal fitness between Ni-Cr alloy and type III gold alloy, according to two finishing line, chamfer and shoulder. As experimental materials, author selected type III gold alloy and Ni-Cr alloy (Hicrown) which were popularly used in Korea for the full cast crown. Author prepared the wax patterns with milled stainless steel die and ring. The wax patterns were invested, burnouted, and casted. The maginal discrepancy was measured with scanning electron microscope. Author obtained the following results from this study. 1. The maginal fitness of Type III gold alloy was not significantly different from that of Ni-Cr alloy (Hi-crown). 2. There is no significant difference between chamfer and shoulder in case of Type III gold alloy. 3. The maginal fitness of chamfer type is significantly superior to that of shoulder type in the Ni-Cr alloy (Hi-Crown).

• The Journal of Advanced Prosthodontics
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• 제2권2호
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• pp.33-38
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• 2010

PURPOSE. Marginal fit is a very important factor considering the restoration's long-term success. However, adding porcelain to copings can cause distortion and lead to an inadequate fit which exposes more luting material to the oral environment and causes secondary caries. The purpose of this study was to compare the marginal fit of 2 different all-ceramic crown systems before and after porcelain veneering. This study was also intended to verify the marginal fit of crowns originated from green machining of partially sintered blocks of zirconia (Lava CAD/CAM system) and that of crowns obtained through machining of fully sintered blocks of zirconia (Digident CAD/CAM system). MATERIALS AND METHODS. 20 crowns were made per each system and the marginal fit was evaluated through a light microscope with image processing (Accura 2000) at 50 points that were randomly selected. Each crown was measured twice: the first measurement was done after obtaining a 0.5 mm coping and the second measurement was done after porcelain veneering. The means and standard deviations were calculated and statistical inferences among the 2 groups were made using independent t-test and within the same group through paired t-test. RESULTS. The means and standard deviations of the marginal fit were $61.52{\pm}2.88{\mu}m$ for the Digident CAD/CAM zirconia ceramic crowns before porcelain veneering and $83.15{\pm}3.51{\mu}m$ after porcelain veneering. Lava CAD/CAM zirconia ceramic crowns showed means and standard deviations of $62.22{\pm}1.78{\mu}m$ before porcelain veneering and $82.03{\pm}1.85{\mu}m$ after porcelain veneering. Both groups showed significant differences when analyzing the marginal gaps before and after porcelain veneering within each group. However, no significant differences were found when comparing the marginal gaps of each group before porcelain veneering and after porcelain veneering as well. CONCLUSION. The 2 all-ceramic crown systems showed marginal gaps that were within a reported clinically acceptable range of marginal discrepancy.

• 한국산업융합학회 논문집
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• 제26권4_2호
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• pp.561-570
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• 2023

This study was to evaluate the effect of different rinsing times and methods on the accuracy of temporary prostheses fabricated by 3D printing method. Sixty temporary prostheses were fabricated with LCD types of 3D printer(Halot-Sky, Creality, Shenzhen, China) and divided into six groups (n = 10) based on rinsing times and methods. All specimens were rinsed with 99% isopropanol alcohol for 5 and 10 min using three methods-hand washed, ultrasonic cleaning, and automated washing. All specimens were polymerized for 3 minutes under the same conditions. The marginal and internal gaps of specimens were examined using a replica technique. The light-body silicone thickness was measured at 6 reference points(Absolute marginal discrepancy, Marginal, Chamfer, Axial, Angle, and Occlusal gap). All measurements were performed by a stereomicroscope. Reference point images were taken at 100× magnification and then measured using an image analysis program. Statistical analysis was performed using Two-way ANOVA, One-way ANOVA, and the Kruskal-Wallis test (p = .05). The marginal and internal gaps were statistically different according to the rinsing methods and rinsing times(p < .001). In the rinsing time, the temporary prosthesis rinsed for 5 minutes group showed higher accuracy than 10 minutes group. In the rinsing method, the hand washing group showed higher accuracy than the automated washing group.