• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2007년도 춘계학술대회 논문집
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• pp.7-8
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• 2007

• 대한치과기공학회지
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• 제43권2호
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• pp.42-47
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• 2021

Purpose: The purpose of this study was to evaluate the stability of abutment screws used with the zirconia fixture-based implant system and compare them with those used with the existing titanium fixture system via the finite element method. Methods: A single implant-supported restoration was designed for the finite element analysis. A universal analysis program was used to set 8 occlusal points along the direction to the long axis of the implant, and an occlusal load of 700 N was applied. Results: In all models (Zir and Ti-fixture model), the screw threads presented with the highest von Mises stress (VMS) values, whereas the head and end presented with the lowest VMS values. The VMS of the screw used in the zirconia-fixture model was 5.97% lower than that used in the titanium-fixture model (261.258 vs. 276.911 MPa, respectively) despite statistical significance. Furthermore, the zirconia fixture (352.912 MPa) had a higher stress value (8.42%) than the titanium fixture (332.331 MPa). In a completely tightened titanium fixture implant system, the stress was concentrated in the implant-abutment connection interface, the zirconia fixture presented with a stable stress distribution. Conclusion: Although the zirconia fixture demonstrated a high VMS value, owing to the stiffness and elasticity coefficients of the material, the stress generated in the abutment screws was similar in all models. In conclusion, the zirconia fixture-based implant system presented with a more stable stress distribution in the abutment screws than the titanium fixture-based implant system.

• The Journal of Advanced Prosthodontics
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• 제14권2호
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• pp.96-107
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• 2022

PURPOSE. Microstructural and physico-mechanical characterization of highly translucent zirconia, prepared by milling technology (CAD-CAM) and repeated firing cycles, was the main aim of this in vitro study. MATERIALS AND METHODS. Two groups of samples of two commercial highly-translucent yttria-stabilized dental zirconia, VITA YZ-HT^White (Group A) and Zolid HT + White (Group B), with dimensions according to the ISO 6872 "Dentistry - Ceramic materials", were prepared. The specimens of each group were divided into two subgroups. The specimens of the first subgroups (Group A₁ and Group B₁) were merely the sintered specimens. The specimens of the second subgroups (Group A₂ and Group B₂) were subjected to 4 heat treatment cycles. The microstructural features (microstructure, density, grain size, crystalline phases, and crystallite size) and four mechanical properties (flexural strength, modulus of elasticity, Vickers hardness, and fracture toughness) of the subgroups (i.e. before and after heat treatment) were compared. The statistical significance between the subgroups (A₁/A₂, and B₁/B₂) was evaluated by the t-test. In all tests, P values smaller than 5% were considered statistically significant. RESULTS. A homogenous microstructure, with no residual porosity and grains sized between 500 and 450 nm for group A and B, respectively, was observed. Crystalline yttria-stabilized tetragonal zirconia was exclusively registered in the X-ray diffractograms. The mechanical properties decreased after the heat treatment procedure, but the differences were not statistically significant. CONCLUSION. The produced zirconia ceramic materials can be safely (i.e., according to the ISO 6872) used in extensive fixed prosthetic restorations, such as substructure ceramics for three-unit prostheses involving the molar restoration and substructure ceramics for prostheses involving four or more units. Consequently, milling technology is an effective manufacturing technology for producing zirconia substructures for dental fixed all-ceramic prosthetic restorations.

• 한국산학기술학회논문지
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• 제15권7호
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• pp.4329-4335
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• 2014

본 연구의 목적은 금속 도재관과 지르코니아 도재관 보철물의 하부 구조물인 금속과 상부 도재의 결합강도 (금속군), 하부 구조물인 지르코니아와 상부 도재의 전단결합강도 (지르코니아군)를 결정함에 있어서 각각 하부 구조물인 금속과 지르코니아의 표면 처리를 다르게 하였을 때, 전단결합강도에 미치는 영향을 평가하고자 한다. 금속군에서는 금속 표면에 각각 아무 처리를 하지 않은 집단(NM), 모래분사를 실시한 집단(SM), 불투명 도재를 도포한 집단(OM), 모래분사와 함께 불투명 도재를 도포한 집단(SOM) 총 4집단으로 나누어 실시하였고, 지르코니아군에서는 아무 처리를 하지 않은 집단(NZ), 표면에 모래 분사를 실시한 집단(SZ), 지르코니아 표면에 이장재(지르라이너)를 처리한 집단(LZ), 모래분사와 이장재 처리를 함께한 집단(SLZ) 총 4집단으로 시편을 제작하였다. 금속군과 지르코니아군 각각의 4집단의 표면 처리에 따른 전단결합강도에 영향이 있는지 알아보기 위하여 SPSS를 사용하여 일원배치 분산분석을 시행하였다. 금속 도재관의 경우 하부 구조물인 금속 표면에 모래분사를 한 후 불투명 도재를 도포하는 것이 가장 권장되며, 지르코니아 도재관의 경우 하부 구조물인 지르코니아 표면에 모래분사를 한 후 지르라이너를 도포하는 것이 권장된다.

• The Journal of Advanced Prosthodontics
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• 제5권3호
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• pp.296-304
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• 2013

PURPOSE. The aim of this study was to evaluate the effect of polishing and glazing on the color and spectral distribution of monolithic zirconia. MATERIALS AND METHODS. Forty-five monolithic zirconia specimens ($16.3mm{\times}16.4mm{\times}2.0mm$) were fabricated and divided into 5 groups according to the number of A2-coloring liquid applications (Group I to V). Each group was divided into 3 subgroups according to the method of surface treatments (n=3): N: no treatment; P: polishing; G: glazing. Color and spectral distribution of five different areas of each specimen were measured according to CIELAB color space in the reflectance mode relative to the standard illuminant D65 on a reflection spectrophotometer. Data were analyzed using one-way ANOVA followed by Tukey's HSD test, Pearson correlation and regression analysis (${\alpha}$=.05). RESULTS. There was a significant difference in CIE $L^*$ between Subgroup N and P, and in CIE $b^*$ between Subgroup P and G in each group. Spectral reflectance generally decreased in Subgroup P and G in comparison with Subgroup N. Color differences between Subgroup P and G were within the perceptibility threshold (${\Delta}E{^*}_{ab}$ < 3.7) in most groups. Highly significant correlation was found between CIE $b^*$ and each subgroups as the number of coloring liquid applications increased ($R^2$ >0.88, P<.001). CONCLUSION. A perceptible color difference can be detected after polishing of monolithic zirconia. Polishing decreases the lightness, and glazing also decreases the lightness, but increases the yellowness of monolithic zirconia.

• The Journal of Advanced Prosthodontics
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• 제5권2호
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• pp.118-125
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• 2013

PURPOSE. The purpose of this study was to evaluate the effect of the span length on the fit of zirconia framework fabricated using CAD/CAM system. MATERIALS AND METHODS. Abutments for single, 4-unit and 6-unit fixed partial prostheses were fabricated. Ten zirconia frameworks were fabricated for each group. The marginal and internal gap were presented by means of replica technique and measured by measuring microscope ($AXIO^{(R)}$, Carl Zeiss, Rochester, NY) and software (I-$solution^{(R)}$, IMT i-solution Inc., Vancouver, BC, Canada). The results were statistically analyzed by multivariate analysis test and Dunnett T3 test for post hoc test (${\alpha}$=.05). RESULTS. There were statistically significant differences at 2, 4, 7, 8 points (mesio-distal section) and b, d, e, f, g (labio-lingual section). In some marginal reference points of 6-unit group (P<.05), the marginal gap were larger than 120 ${\mu}m$. CONCLUSION. Span length of zirconia core may have an influence on marginal and internal fit. Within the limitation of this study, the increase of span length of zirconia framework of 6 or more-unit fixed partial denture may decrease the marginal and internal fit.

• 대한치과기공학회지
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• 제39권4호
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• pp.235-242
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• 2017

Purpose: The aim of this study was to evaluate the marginal and internal gap of zirconia copings fabricated by CAD/CAM system and to research the effect of cement space on the fit of zirconia prosthesis. Methods: Zirconia copings were designed using 3shape software and then milled from presintered zirconia blocks by Kavo dental milling machine. The cement space was set at $0{\mu}m$ around the margins for all groups, and additional cement space appling 1 mm above the finish lines of tooth. The samples were classified into 4 groups according to the cement space setting(Cs-0, Cs-40, Cs-80, Cs-120). Replica technique used to investigate marginal and internal gap. The silicone film thickness was recorded using a optical microscope with image software analysis system at 75${\times}$magnification. The assessment performed on the six points in bucco-lingual and mesio-distal sections(4 groups, 10 copings per group, 12 measuring points per coping). The data were statistically analyzed with one-way ANOVA followed by pair-wise Tukey's post hoc tests(${\alpha}$<0.05). Results: Better marginal and internal fit values were exhibited by $80{\mu}m$ cement space. The results showed that different cement space values had statistically significant effect on the marginal and internal gap of zirconia copings(p<0.001). The gap of margin and axial wall area was smaller than that the gap of occlusal area in all groups(p<0.001). Conclusion : Effect of different cement spaces on the marginal and internal gap of zirconia copings.

• 한국산학기술학회논문지
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• 제22권4호
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• pp.124-130
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• 2021

치과보철물의 심미적 결과를 조절하는 중요한 요인은 반투명도이며, 지르코니아 착색제의 건조 정도가 반투명도에 어떠한 영향을 미치는지 알아보고자 한다. 실험을 위해서 지르코니아 블록별로 원형 시편을 총 90개 제작하였다. 그 다음 지르코니아 시편을 착색제로 180초 침적 후 미건조(0초), 중간건조(30초), 완전건조(30분)의 건조시간(Dry time)을 부여한 후 지르코니아 소결로를 이용하여 원형 시편을 소결하였다. 분광광도계(Spectrophotometer CM-3600A, Konica Minolta, Japan)를 이용하여 흑색표준타일과 백색표준타일 위에 시편을 놓고, 표준광원 D65의 조건에서 정반사광 제거방식으로 지르코니아 원형 시편을 각각 측정하였다. 시편당 총 3번씩 반복측정하였다. 지르코니아의 건조시간에 따른 반투명도를 비교 분석하기 위하여 One-way ANOVA를 시행하였다. 지르코니아 종류별, 착색제에 따라 반투명도는 통계적으로 차이가 있었고(P < 0.001), 건조시간에 따라서는 통계적으로 차이는 없었다(P > 0.922). 그러나, 완전건조인 상태일 때, 반투명도 값이 작은 것으로 나타나 건조가 잘 될수록 지르코니아 색상이 투명하다는 것을 알 수 있었다.

• The Journal of Advanced Prosthodontics
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• 제14권3호
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• pp.173-181
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• 2022

PURPOSE. This analysis aimed to evaluate the intaglio surface trueness, antagonist's wear volume loss, and fracture resistance of full-contour crowns of (Y, Nb)-stabilized fully-sintered zirconia (FSZ), 4 mol% or 5 mol% yttria-stabilized partially sintered zirconia (4YZ or 5YZ) with high-speed sintering. MATERIALS AND METHODS. A total of 42 zirconia crowns were separated into three groups: FSZ, 4YZ, and 5YZ (n = 14). The intaglio surface trueness of the crowns was evaluated at the inner surface, occlusal, margin, and axial areas and reported as root-mean-square, positive and negative average deviation. Half of the specimens were aged for 120,000 cycles in the chewing simulator, and the wear volume loss of antagonist was measured. Before and after chewing, the fracture load was measured for each group. The trueness values were analyzed with Welch's ANOVA, and the wear volume loss with the Kruskal-Wallis tests. Effect of the zirconia type and aging on fracture resistance of crowns was tested using two-way ANOVA. RESULTS. The intaglio surface trueness measured at four different areas of the crown was less than 50 ㎛, regardless of the type of zirconia. No significant P in wear volume loss of antagonists were detected among the groups (P > .05). Both the type of zirconia and aging showed statistically significant effects on fracture resistance (P < .05). CONCLUSION. The full-contour crowns of FSZ as well as 4YZ or 5YZ with high-speed sintering were clinically acceptable, in terms of intaglio surface trueness, antagonist's wear volume loss, and fracture resistance after simulated mastication.

• 대한치과보철학회지
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• 제57권2호
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• pp.134-141
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• 2019

목적: 본 연구에서는 리튬 디실리케이트-지르코니아 이중도재관과 단일구조 지르코니아로 제작된 구치부 고정성 임플란트 지지 보철물의 2년간의 임상적 결과를 비교하고자 하였다. 대상 및 방법: 2015년에서 2018년 사이 부산대학교 치과병원에 내원하여 치료받은 총 17명의 환자(남성: 12, 여성: 5)를 대상으로 60개의 구치부 고정성 임플란트 지지 보철물을 제작하였다(LP. Lithium disilicate pressed zirconia prostheses: n = 30, MZ. Monolithic zirconia prostheses: n = 30) 보철물 제작 후 2년간의 추적 관찰을 통해 임플란트 생존율, 변연골 흡수량, 치주낭 깊이, 치태지수, 출혈지수, 치석지수 및 합병증을 평가하였다. 결과: 모든 임플란트가 기능적 문제와 동요도 없이 100%의 생존율을 보였다. 변연골 흡수량은 관찰 12개월에 LP군이 MZ군 보다 더 적었으며 (P < .05), 임상 검사시 관찰 12개월의 치주낭 깊이 및 치석 지수는 LP군에서 더 높았다 (P < .05). 주된 합병증으로 MZ군에서 7개에서 1.5 mm 이상의 골흡수가 관찰되었으며, LP군에서 2개의 chipping이 관찰되었다. 결론: 본 연구의 한계 내에서, 구치부 임플란트 지지 보철물에서 리튬 디실리케이트가 프레스된 지르코니아 보철물은 단일구조 지르코니아 보철물과 함께 예지성 있는 치료방법으로 판단된다.