• 대한심미치과학회지
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• 제23권2호
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• pp.77-79
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• 2014

There are several factors affected fractures of full contour zirconia (FCZ) dental prosthesis in laboratory process. First, residual moisture can cause zirconia cracks. Complete dry is requisite before zirconia sintering to prevent zirconia cracks. Second, slow cooling rate is essential to prevent cracks during zirconia sintering process. Cracks in bridge pontic area, thick dental implant prosthesis can be prevented by slow cooling rate such as 3 degree Celsius per minute during zirconia sintering. Third, slow heating rate and slow cooling rate during staining and glazing procedure is necessary to inhibit thermal shock of sintered dental zirconia. Lower preheat temperature of porcelain furnace is recommended. Finally, using diamond disc to open embrasure can lead cracks.

• 대한심미치과학회지
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• 제24권2호
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• pp.101-121
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• 2015

지르코니아 폴리크리스탈은 (Y-TZP) 다른 치과용 세라믹에 비해 기계적 강도와 파절저항성이 우수하다. 지르코니아 기반 세라믹은 캐드캠 시스템을 바탕으로 고정식 수복물 제작에 성공적으로 소개되어 왔다. 이는 고정식 수복물을 위한 금속 구조물의 임상적 대안으로 제시되었다. 지르코니아 수복물의 가장 흔한 합병증은 상부 도재의 파절이다. 다른 옵션은 고도로 반투명한 지르코니아를 전부지르코니아 고정식 수복물로 사용하는 것이다. 본 논문에서는 전부지르코니아 수복물의 장점, 지르코니아 수복물의 임상적용, 지대치 삭제, 대합치 마모, 지르코니아와 레진시멘트와의 접착, 그리고 기공소와의 의사소통에 관하여 보고하였다.

• 대한치과기공학회지
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• 제35권2호
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• pp.121-126
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• 2013

Purpose: The aim of this research was to investigate difference in shear bond strengths of full-contour zirconia layered with porcelain. Methods: Disk-shaped (diameter: 12.0 mm; height: 3.0 mm) zirconia were randomly divided into six groups according to the surface conditioning method to be applied (N=90, n=15 per group): group 1-contol group(ZC); group 2-airborne particle abrasion with $50-{\mu}m\;Al_2O_3(5A)$; group $3-50-{\mu}m\;Al_2O_3$ + liner(5AL), group $4-110-{\mu}m\;Al_2O_3(1A)$; group $5-110-{\mu}m\;Al_2O_3$ + liner(1AL); group 6-liner(LC). On each block, zirconia porcelain was build up according to manufacturer's instructions. All samples were fixed with measuring jigs and shear bond strength were measured with Universal testing machine. Collected data were analyzed using SPSS(Statistical Package for Social Sciences) Win 12.0 statistics program. Results: LC showed the highest value($29.92{\pm}2.55$ MPa) and ZC showed the lowest value($13.22{\pm}1.37$ MPa). Zirconia liner and Alumina oxide groups was significantly higher shear bond strength than control(p<0.05). 5A (without liner $22.18{\pm}2.37$, with liner $22.84{\pm}1.74$ MPa) was higher shear bond strength than $110{\mu}m$ (without liner $20.18{\pm}2.38$, with $20.71{\pm}2.67$). Conclusion: Surface treatments may have advantage in bond strength improvement for full-contour zirconia layered with porcelain.

• 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.

• 대한심미치과학회지
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• 제25권2호
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• pp.79-87
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• 2016

당일수복 보철물 제작을 위해 디지털 프로세스 사용은 필수적이다. 이러한 디지털 프로세스는 구강스캔, 컴퓨터를 이용한 보철물을 디자인 과정(CAD)과 보철물을 가공하는 과정(CAM)을 포함한다. 지르코니아의 굴곡강도는 900Mpa로 리튬디실리케이트의 400MPa보다 더 단단하지만, 리튬디실리케이트를 이용한 보철물 기공시간이 지르코니아와 비교하여 더 짧기에 당일수복 보철물 제작시 리튬디실리케이트 사용이 선호되었다. 하지만, TZI C 와 LUXEN Enamel 와 같은 새로운 소재의 지르코니아가 출시되고, 새로운 소결방식이 개발되어 지르코니아 기공시간을 단축시킬수 있게 되었고, 높은 투명도의 풀지르코니아 크라운을 짧은 시간 안에 제작할 수 있게 되었다. 이러한 발전은 당일 풀지르코니아 보철수복을 현실로 이끌고 있다.

• The Journal of Advanced Prosthodontics
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• 제7권2호
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• pp.146-150
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• 2015

PURPOSE. This in vitro study aimed to compare the failure load and failure characteristics of two different zirconia framework designs of premolar crowns when subjected to static loading. MATERIALS AND METHODS. Two types of zirconia frameworks, conventional 0.5 mm even thickness framework design (EV) and 0.8 mm cutback of full contour crown anatomy design (CB), were made for 10 samples each. The veneer porcelain was added on under polycarbonate shell crown made by vacuum of full contour crown to obtain the same total thickness of the experiment crowns. The crowns were cemented onto the Cobalt-Chromium die. The dies were tilted 45 degrees from the vertical plane to obtain the shear force to the cusp when loading. All crowns were loaded at the lingual incline of the buccal cusp until fracture using a universal testing machine with cross-head speed 0.5 mm/min. The load to fracture values (N) was recorded and statistically analyzed by independent sample t-test. RESULTS. The mean and standard deviations of the failure load were $1,170.1{\pm}90.9$ N for EV design and $1,450.4{\pm}175.7$ N for CB design. A significant difference in the compressive failure load was found (P<.05). For the failure characteristic, the EV design was found only cohesive failures within veneering porcelain, while the CB design found more failures through the zirconia framework (8 from 10 samples). CONCLUSION. There was a significant difference in the failure load between two designs, and the design of the framework influences failure characteristic of zirconia crown.

• Restorative Dentistry and Endodontics
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• 제41권2호
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• pp.106-113
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• 2016

Objectives: This study evaluated the effects of different surface conditioning methods on the bond strength of orthodontic brackets to glazed full-zirconia surfaces. Materials and Methods: Glazed zirconia (except for the control, Zirkonzahn Prettau) disc surfaces were pre-treated: PO (control), polishing; BR, bur roughening; PP, cleaning with a prophy cup and pumice; HF, hydrofluoric acid etching; AA, air abrasion with aluminum oxide; CJ, CoJet-Sand. The surfaces were examined using profilometry, scanning electron microscopy, and electron dispersive spectroscopy. A zirconia primer (Z-Prime Plus, Z) or a silane primer (Monobond-S, S) was then applied to the surfaces, yielding 7 groups (PO-Z, BR-Z, PP-S, HF-S, AA-S, AA-Z, and CJ-S). Metal bracket-bonded specimens were stored in water for 24 hr at $37^{\circ}C$, and thermocycled for 1,000 cycles. Their bond strengths were measured using the wire loop method (n = 10). Results: Except for BR, the surface pre-treatments failed to expose the zirconia substructure. A significant difference in bond strengths was found between AA-Z ($4.60{\pm}1.08MPa$) and all other groups ($13.38{\pm}2.57-15.78{\pm}2.39MPa$, p < 0.05). For AA-Z, most of the adhesive remained on the bracket. Conclusions: For bracket bonding to glazed zirconia, a simple application of silane to the cleaned surface is recommended. A zirconia primer should be used only when the zirconia substructure is definitely exposed.

• 대한치과보철학회지
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• 제50권3호
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• pp.198-203
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• 2012

과도한 치아 마모는 교합면에 손상을 야기하고, 치수 병변, 교합 부조화, 기능장애, 심미적 문제 등을 야기할 수 있다. 과도한 치아 마모를 갖고 있는 환자들을 치료하고자 할 때 수직교합고경(vertical dimension of occlusion, VDO)의 상실 여부와 수복을 위한 악간 공간의 적절성 여부에 기반하여 분류를 할 필요가 있다. 본 증례의 환자는 다수 치아들의 마모를 지닌 50세의 남성으로, 과도한 치아 마모가 있지만 수직교합고경의 상실은 없으며 수복을 위한 악간 공간이 부족하였다. 이러한 경우 수직교합고경을 증가시켜 치료를 진행하는 것을 고려할 수 있다. 수직교합고경의 증가를 필요한 범위 내에서 최소로 줄이고, 증가된 수직교합고경 상에서 안정화 기간을 거친 뒤 안정된 교합 접촉을 제공할 수 있다면, 수직고경 증가를 동반한 치료법은 안정성을 가질 수 있다. 본 남성 환자를 치료하기 위해 수직고경의 증가를 동반하여 전치부와 구치부에서 단일구조 지르코니아를 이용한 고정성 보철물로 수복을 하였다. 일련의 치료과정을 통하여 기능적인 면과 심미적인 면에서 만족스러운 결과를 얻었기에 보고하는 바이다.

• 대한치과교정학회지
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• 제45권6호
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• pp.299-307
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• 2015

Objective: The aims of this study were to compare the shear bond strength between orthodontic metal brackets and glazed zirconia using different types of primer before applying resin cement and to determine which primer was more effective. Methods: Zirconia blocks were milled and embedded in acrylic resin and randomly assigned to one of four groups: nonglazed zirconia with sandblasting and zirconia primer (NZ); glazed zirconia with sandblasting, etching, and zirconia primer (GZ); glazed zirconia with sandblasting, etching, and porcelain primer (GP); and glazed zirconia with sandblasting, etching, zirconia primer, and porcelain primer (GZP). A stainless steel metal bracket was bonded to each target surface with resin cement, and all specimens underwent thermal cycling. The shear bond strength of the specimens was measured by a universal testing machine. A scanning electron microscope, three-dimensional optical surface-profiler, and stereoscopic microscope were used to image the zirconia surfaces. The data were analyzed with one-way analyses of variance and the Fisher exact test. Results: Group GZ showed significantly lower shear bond strength than did the other groups. No statistically significant differences were found among groups NZ, GP, and GZP. All specimens in group GZ showed adhesive failure between the zirconia and resin cement. In groups NZ and GP, bonding failed at the interface between the resin cement and bracket base or showed complex adhesive and cohesive failure. Conclusions: Porcelain primer is the more appropriate choice for bonding a metal bracket to the surface of a full-contour glazed zirconia crown with resin cement.

• 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.