• The Journal of Advanced Prosthodontics
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• 제1권3호
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• pp.113-117
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• 2009

STATEMENT OF PROBLEM. Recently Yttrium-stabilized tetragonal zirconia polycrystal (Y-TZP) has been introduced due to superior flexural strength and fracture toughness compared to other dental ceramic systems. Although zirconia has outstanding mechanical properties, the phenomenon of decrease in the life-time of zirconia resulted from degradation in flexural strength after low temperature aging has been reported. PURPOSE. The objective of this study was to investigate degradation of flexural strength of Y-TZP ceramics after various low temperature aging treatments and to evaluate the phase stability and micro-structural change after aging by using X-ray diffraction analysis and a scanning electron microscope (SEM). MATERIAL AND METHODS. Y-TZP blocks of Vita In-Ceram YZ (Vita Zahnfabrik, Bad $S\ddot{a}ckingen$, Germany) were prepared in 40 mm (length) $\times$ 4 mm (width) $\times$ 3 mm (height) samples. Specimens were artificially aged in distilled water by heat-treatment at a temperature of 75, 100, 125, 150, 175, 200, and $225^{\circ}C$ for 10 hours, in order to induce the phase transformation at the surface. To measure the mechanical property, the specimens were subjected to a four-point bending test using a universal testing machine (Instron model 3365; Instron, Canton, Mass, USA). In addition, X-ray diffraction analysis (DMAX 2500; Rigaku, Tokyo, Japan) and SEM (Hitachi s4700; Jeol Ltd, Tokyo, Japan) were performed to estimate the phase transformation. The statistical analysis was done using SAS 9.1.3 (SAS institute, USA). The flexural strength data of the experimental groups were analyzed by one-way analysis of variance and to detect statistically significant differences ($\alpha$= .05). RESULTS. The mean flexural strength of sintered Vita In-Ceram YZ without autoclaving was 798 MPa. When applied aging temperature at below $125^{\circ}C$ for 10 hours, the flexural strength of Vita In-Ceram YZ increased up to 1,161 MPa. However, at above $150^{\circ}C$, the flexural strength started to decrease. Although low temperature aging caused the tetragonal-to-monoclinic phase transformation related to temperature, the minimum flexural strength was above 700 MPa. CONCLUSION. The monoclinic phase started to appear after aging treatment above $100^{\circ}C$. With the higher aging temperature, the fraction of monoclinic phase increased. The ratio of monoclinic/tetragonal + monoclinic phase reached a plateau value, circa 75% above $175^{\circ}C$. The point of monoclinic concentration at which the flexural strength begins to decrease was between 12% and 54%.

• 한국산학기술학회논문지
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• 제21권3호
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• pp.335-341
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• 2020

본 연구의 목적은 shear bond strength을 이용하여 pressed lithium disilicate 전장도재와 zirconia core의 접착을 비교 분석하는 것이다. Zirconia blank(Zirtooth, HASS, Gangneung, Korea)에 각 pressed ceramic(IPS e.max Zirpress, Vita PM9, GC Initial IQ, HASS Rosetta UP)이 적용된 시편을 제작하였다(N=40). 전단결합강도를 비교 평가하기 위해 The Schmitz-Schulmeyer test method을 이용하였고 산출된 파괴하중의 값을 분석했다. 산출된 네 가지 전단결합강도 값들 간의 평균 비교는 일원분산분석(one-way ANOVA)을 통해 이루어졌고, Tukey의 사후검정을 실시하여 서로 간의 평균 차이가 통계적으로 유의함을 검증하였다. 또 파절면의 3D 분석을 통하여 파괴 표면을 관찰하여, 그 파괴 양상도 분류하였다. 실험군별 전단결합강도는 IPS e.max Zirpress 16.69±3.11MPa, VITA PM9 14.21±3.63MPa, GC Initial IQ 11.17±2.92MPa, HASS Rosetta SM 27.90±5.71MPa이었으며, Lithium disilicate ceramic veneer(HASS Rosetta SM)의 결합 강도는 다른 제품들보다 통계적으로 유의하게 높았다(p<0.05). 또, 파괴면의 유형 분류 결과, 모든 시편에서 cohesive 파괴는 관찰되지 않았고 주로 adhesive와 cohesive가 같이 조합된 파괴 유형이 관찰되었다. 본 연구 결과에 의해서 pressed lithium disilicate 전장도재가 기존의 pressed to zirconia system보다 나은 접착력을 보여주었다.

• 대한소아치과학회지
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• 제29권3호
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• pp.362-370
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• 2002

최근 20년간 다양한 종류의 심미 수복재가 개발되었고, 특히 지난 5년 동안에는 그 수에 있어서 극적인 증가추세를 보였다. 최근 들어, ormocer라는 새로운 종류의 광중합형 수복재료가 소개되었는데, 화학 분야에서는 이미 오래 전부터 알려져 있던 성분으로, 광학렌즈 등의 표면경화제로 이용되어 오다가 최근 치과용 수복재에 도입되었다. 'Ormocer' 란 'Organically Modified Ceramics'의 약자로 'Ormosils' (Organically Modified Silicates)로도 알려져 있다. 그러나, 이 새로운 수복재에 대한 연구는 아직 미흡한 실정이다. 본 연구에서는 서로 다른 계통의 광중합형 수복재들(Z-100, Surefil, Tetric Ceram, Dyract AP)과 ormocer(Admira)를 압축강도와 굴곡강도 측면에서 비교 평가하고, 구강내 환경과 유사한 조건에서 수분흡수가 그 물성에 미치는 영향을 평가할 목적으로 시도되어 다음과 같은 결과를 얻었다. 1. 1일 후에 측정한 Admira의 압축강도는 Surefil보다는 낮았으나, 다른 재료들과는 유의한 차이를 나타내지 않았다(p>0.05). 2. 1일 후에 측정한 Admira의 굴곡강도는 다른 4종의 재료에 비해서 낮았다(p<0.05). 2일부터는 3종의 복합레진에 비해서 낮았다(p<0.05). 3. 실험기간(30일) 중 hybrid composite resin군(Z-100, Tetric Ceram)과 packable resin(Surefil)군 간에는 압축강도와 굴곡강도에서 유의한 차이가 없었다(p>0.05). 4. 실험에 사용된 5종의 수복재 모두 압축강도와 굴곡강도가 2일까지 증가하다가 7일부터 감소하였다(p<0.05). 5. 각 재료의 시간에 따른 압축강도와 굴곡강도의 변화양상은 통계적으로 유사하였다(p>0.05).

• The Journal of Advanced Prosthodontics
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• 제9권3호
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• pp.200-207
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• 2017

PURPOSE. In this study, three bioceramic materials, [IPS Empress CAD (Ivoclar), IPS e.max CAD (Ivoclar), and Lava Ultimate CAD (3M ESPE)] were treated with three commercial mouthrinses [Listerine, Tantum Verde, and Klorhex]; and changes in colour reflectance and surface roughness values were then quantitatively assessed. MATERIALS AND METHODS. One hundred and twenty ceramic samples, with dimensions of $2{\times}12{\times}14mm$, were prepared and divided into nine sample groups, except three control samples. The samples were immersed in the mouthrinse solutions for 120 hrs, and changes in colour reflectance and surface roughness values were measured by UV light spectrophotometry (Vita Easyshade; VITA Zahnfabrik) and by profilometer device (MitutoyoSurftest SJ-301), respectively. The change of surface roughness was inspected by Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). RESULTS. There was a positive correlation between the ${\Delta}E$ and increase in the surface roughness. Two of the ceramic materials, IPS Empress and Lava Ultimate, were affected significantly by the treatment of the mouthrinse solutions (P<.05). The most affecting solution was Tantum Verde and the most affected material was Lava Ultimate. As expected, the most resistant material to ${\Delta}E$ and chemical corrosion was IPS e max CAD among the materials used. CONCLUSION. This work implied that mouthrinse with lower alcohol content had less deteriorating effect on colour and on the surface morphology of the bioceramic materials.

• The Journal of Advanced Prosthodontics
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• 제4권2호
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• pp.76-83
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• 2012

PURPOSE. Zirconia has been used in clinical dentistry for approximately a decade, and there have been several reports regarding the clinical performance and survival rates of zirconia-based restorations. The aim of this article was to review the literatures published from 2000 to 2010 regarding the clinical performance and the causes of failure of zirconia fixed partial dentures (FPDs). MATERIALS AND METHODS. An electronic search of English peer-reviewed dental literatures was performed through PubMed to obtain all the clinical studies focused on the performance of the zirconia FPDs. The electronic search was supplemented by manual searching through the references of the selected articles for possible inclusion of some articles. Randomized controlled clinical trials, longitudinal prospective and retrospective cohort studies were the focuses of this review. Articles that did not focus on the restoration of teeth using zirconia-based restorations were excluded from this review. RESULTS. There have been three studies for the study of zirconia single crowns. The clinical outcome was satisfactory (acceptable) according to the CDA evaluation. There have been 14 studies for the study of zirconia FPDs. The survival rates of zirconia anterior and posterior FPDs ranged between 73.9% - 100% after 2 - 5 years. The causes of failure were veneer fracture, ceramic core fracture, abutment tooth fracture, secondary caries, and restoration dislodgment. CONCLUSION. The overall performance of zirconia FPDs was satisfactory according to either USPHS criteria or CDA evaluations. Fracture resistance of core and veneering ceramics, bonding between core and veneering materials, and marginal discrepancy of zirconia-based restorations were discussed as the causes of failure. Because of its repeated occurrence in many studies, future researches are essentially required to clarify this problem and to reduce the fracture incident.

• 대한치과보철학회지
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• 제32권2호
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• pp.195-211
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• 1994

The purpose of this study was to evaluate the fracture resistance of the four kinds of dental porcelains for the all-ceramic crown(Vita In-Ceram, Vita Hi-Ceram, IPS-Empress, Vitadur-N) and one kind for the metal-ceramic non(Vita VMK 68) was used as the control group. In order to determine the fracture resistance, the hi-axial flexure strength was measured at a crosshead speed of 0.5mm/min, and the Vickers hadrness was measured at an indentation load of 1kg for 20 seconds. The results obtained were summarized as follows ; 1. The maximum Weibull modulus of 24.61 for Vitadur-N and the minimum one of 852 for IPS-Empress were observed ; the maximum characteristic strength of 353.26MPa for Vita In-Ceram and the minimum that of 63.20MPa for Vitadur-N were also observed. 2. The maximum mean bi-axial flexure strength of 339.12MPa for Vita In-Ceram and thd minimum one of 61.99MPa for Vitadur-N were calculated. Results of the Scheffe test indicated that the statistically significant difference(P<0.05) existed between Vita In-Ceram or Vita Hi-Ceram and the others ; also between IPS-Empress and Vitadur-N. 3. The maximum mean hardness of $980.55kg/mm^2$ for Vita VMK 68 appeared. Results of the Scheffe test indicated that statistically significant difference(P<0.05) existed between Vita In-Ceram or Vita Hi-Ceram and the others ; also between IPS-Empress and Vita VMK 68.

• The Journal of Advanced Prosthodontics
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• 제8권5호
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• pp.339-344
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• 2016

PURPOSE. Pre-surface treatments of coping materials have been recommended to enhance the bonding to the veneering ceramic. Little is known on the effect on shear bond strength, particularly with new coping material. The aim of this study was to investigate the shear bond strength of veneering ceramic to three coping materials: i) metal alloy (MA), ii) zirconia oxide (ZO), and iii) lithium disilicate (LD) after various pre-surface treatments. MATERIALS AND METHODS. Thirty-two (n = 32) discs were prepared for each coping material. Four pre-surface treatments were prepared for each sub-group (n = 8); a) no treatment or control (C), b) sandblast (SB), c) acid etch (AE), and d) sandblast and acid etch (SBAE). Veneering ceramics were applied to all discs. Shear bond strength was measured with a universal testing machine. Data were analyzed with two-way ANOVA and Tukey's multiple comparisons tests. RESULTS. Mean shear bond strengths were obtained for MA ($19.00{\pm}6.39MPa$), ZO ($24.45{\pm}5.14MPa$) and LD ($13.62{\pm}5.12MPa$). There were statistically significant differences in types of coping material and various pre-surface treatments (P<.05). There was a significant correlation between coping materials and pre-surface treatment to the shear bond strength (P<.05). CONCLUSION. Shear bond strength of veneering ceramic to zirconia oxide was higher than metal alloy and lithium disilicate. The highest shear bond strengths were obtained in sandblast and acid etch treatment for zirconia oxide and lithium disilicate groups, and in acid etch treatment for metal alloy group.

• 구강회복응용과학지
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• 제18권2호
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• pp.113-118
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• 2002

Long bridge가 필요한 구강암종환자에게 자기공명영상을 촬영하여야 하는 경우, fiber reinforced polymer ceramics로 잠정보철물을 제작해준 경우 충분한 파절 저항성과 심미성을 얻을 수 있었다. 하지만, 여기에 대한 장기간의 연구와 관찰이 필요하리라 사료된다.

• 구강회복응용과학지
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• 제18권2호
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• pp.73-80
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• 2002

치과용 임플란트의 세라믹 지대주를 위해 개발된 지르코니아 함유 세라믹 시편의 생체 적합성을 평가하기 위하여 시험관내 세포 독성을 검사를 시행하였다. L929 섬유모세포를 $37^{\circ}C$, 90% 습도, 5% CO2 및 95% 공기의 조건을 유지하는 세포 배양기에서 배양하여 실험에 사용하였다. 배양 2일, 4일, 6일 마다 시편을 넣은 배양 접시 내의 전체 세포 수와 생존 세포 수를 세어 세포 증식과 세포 생존율 검사를 시행하였다. millipore filter test를 이용하여 succinate dehydrogenase 효소 활성을 검사하였으며, 세포막 투과성의 변화를 관찰하기 위해 agar overlay test를 시행하였다. 음성 대조군은 시편을 사용하지 않았으며, 양성 대조군은 시편과 같은 크기의 구리를 사용하여, 다음과 같은 결과를 얻었다. 1. 세포 증식과 세포 생존율 검사에서는 지르코니아 함유 세라믹을 넣은 실험군과 음성 대조군 모두에서 시간이 경과함에 따라 세포가 증식하는 양상을 보였다. 세포 생존율 검사에서도 실험군과 음성 대조군이 유사한 결과를 나타내었다. 2. millipore filter test에서는 실험 시편 모두에서 염색 정도의 변화가 없이 음성 대조군과 동일한 결과를 나타냈다. 반면에 구리 시편을 넣은 양성 대조군에서는 중등도의 세포 독성을 나타냈다. 3. agar overlay test에서도 시편을 넣지 않은 음성 대조군에서는 세포 성장에 변화가 나타나지 않았으며, 실험군에서도 시편 주위로 탈색이 관찰되지 않아서 음성대조군과 같은 결과를 나타냈다. 양성 대조군에서는 심한 세포 독성을 나타내었다. 4. 실험결과, 치과용 임플란트의 세라믹 지대주를 위해 개발된 지르코니아 함유 세라믹 시편은 시험관내 세포 독성을 나타내지 않았다.

• 구강회복응용과학지
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• 제23권4호
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• pp.269-281
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• 2007

Fluoric acid etching is an essential procedure in cementation of reinforced ceramics to tooth surface. But there have been few studies about the changes of surface structure and flexural strength of IPS $Empress^{(R)}$ 2 ceramic according to the etching time. The objectives of this study were to examine the surface structure changes and the difference in biaxial flexural strength of IPS $Empress^{(R)}$ 2 ceramic according to various etching times. Sixty one disk-shaped specimens of IPS $Empress^{(R)}$ 2 ceramic($14mm{\times}1.2mm$) were fabricated for the biaxial flexural strength test and SEM analysis according to the manufacturer's recommendations. Sixty specimens were divided into 6 groups(n=10) according to the time of HF acid etching(0, 20, 180 and 300s)and silane/resin cement application. Each disk was loaded using a piston-on-3 ball biaxial configuration in a universal testing machine. The failure loads(N) were recorded, and the biaxial flexural strength for each disk was calculated. A one-way analysis of variance and independent t-test on transformed fracture strength data were used to determine significant differences between groups. The groups of no cementation showed a trend toward progressive weakening with increasing the etching time. However, this was not statistically significant at p=0.05 level. The groups of resin cementation exhibited no apparent trend in their mean strength values. SEM photomicrographs showed very different results of etching. Within the conditions of this study, alteration of surface topography by acid etching does not have a deleterious effect on the biaxial flexural strength of IPS $Empress^{(R)}$ 2 ceramic.