• The Journal of Advanced Prosthodontics
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• 제5권2호
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• pp.92-97
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• 2013

PURPOSE. All-ceramic crowns are subject to fracture during function. To minimize this common clinical complication, zirconium oxide has been used as the framework for all-ceramic crowns. The aim of this study was to compare the fracture strengths of two computer-aided design/computer-aided manufacturing (CAD/CAM) zirconia crown systems: Lava and Digident. MATERIALS AND METHODS. Twenty Lava CAD/CAM zirconia crowns and twenty Digident CAD/CAM zirconia crowns were fabricated. A metal die was also duplicated from the original prepared tooth for fracture testing. A universal testing machine was used to determine the fracture strength of the crowns. RESULTS. The mean fracture strengths were as follows: $54.9{\pm}15.6$ N for the Lava CAD/CAM zirconia crowns and $87.0{\pm}16.0$ N for the Digident CAD/CAM zirconia crowns. The difference between the mean fracture strengths of the Lava and Digident crowns was statistically significant (P<.001). Lava CAD/CAM zirconia crowns showed a complete fracture of both the veneering porcelain and the core whereas the Digident CAD/CAM zirconia crowns showed fracture only of the veneering porcelain. CONCLUSION. The fracture strengths of CAD/CAM zirconia crowns differ depending on the compatibility of the core material and the veneering porcelain.

• 대한치과보철학회지
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• 제44권3호
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• pp.275-283
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• 2006

Statement of problem. There have been many studies about marginal discrepancy of single restorations made by various systems and materials. However most of the statistical inferences are not definite because of sample size, measurement number, measuring instruments, etc, and there have been few studies about the marginal fit of the Digident CAD/ CAM zirconia ceramic crowns. Purpose. The purpose of this study was to compare the marginal fit of the anterior single restorations made by using the Digident CAD / CAM zirconia ceramic crowns with metal-ceramic restorations and to obtain more accurate information by using a large enough sample size and by making sufficient measurements per specimen. Material and Methods. The crowns were made from one extracted maxillary central incisor pre-pared with a 1mm shoulder margin and $6^{\circ}$ taper walls by milling machine. The in vitro marginal discrepancies of the digident CAD / CAM zirconia ceramic crowns and control groups(metal ceramic crowns) were evaluated and compared. Twenty crowns per each system were fabricated. Measurements of a crown were recorded at 50 points that were randomly selected for marginal gap evaluation. Parametric statistical analysis was performed for the results. Conclusion. Within the limitations of this in vitro study, the following conclusions were drawn: 1. Mean gap dimensions and standard deviations at the marginal opening for maxillary incisal crowns were $88{\pm}10{\mu}m$ for the control (metal-ceramic crowns), $92{\pm}4{\mu}m$ for Digident CAD / CAM zirconia ceramic crowns. 2. Marginal gap between Digident CAD / CAM zirconia ceramic crowns and metal ceramic crowns did not show significant difference (P>.05). 3. The Digident CAD/ CAM zirconia ceramic crowns and metal ceramic crowns showed clinically acceptable marginal discrepancy.

• 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.

• 대한심미치과학회지
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• 제15권2호
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• pp.7-14
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• 2006

• 대한치과보철학회:학술대회논문집
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• 대한치과보철학회 2005년도 추계학술대회
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• pp.84-84
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• 2005

• 대한치과보철학회지
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• 제46권4호
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• pp.409-419
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• 2008

연구목적: 인간은 누구나 아름다움을 추구하는 욕망을 가지고 있으며 치의학 분야에서도 심미란 중요한 치료목적 중의 하나이다. 최근에는 부하를 많이 받는 구치부에까지 심미적 요구가 증가됨에 따라 지르코니아를 이용한 코아의 사용이 증가되고 있다. 기본적으로 zirconium oxide의 색상은 흰색-상아색이며, 만약 하부구조물이 이미 인접치의 색조와 조화되어 있다면 색조 부여에 훨씬 유리할 것이며, 원하는 색상을 내기 위하여 필요한 도재층의 두께를 감소시킬 수 있어 더 많은 치질을 보존할 수 있을 것이다. 연구재료 및 방법: 이 연구에서는 현재 임상에서 사용되고 있는 3가지 지르코니아 시스템의 코아 색조 부여 유무와 도재층의 두께가 전부도재관의 색조에 미치는 영향을 알아보기 위하여, 각 시스템의 코아에 색조 부여를 한 실험군과 부여하지 않은 실험군으로 구분하여 코아에 축성한 도재층의 두께에 따른 각각의 색조를 분광측색장치를 이용하여 CIE $L^{*}a^{*}b^{*}$ 색체계를 사용하여 색차를 비교, 분석하였다. 결과: 도재층 0.5 mm 축성시 Lava Frame Zirconia 군과 KaVo Everest Zirconia 군은 코아의 색조 부여 유무에 따라 육안으로 인지 가능한 색조 차이를 보이지 않았으나, Digident CAD/CAM Zirconia 군의 경우 육안으로 인지 가능한 색조차이를 보여 하부 코아의 색조가 충분히 피개되지 못하는 것으로 나타났다. 또한 도재층의 두께를 0.4 mm로 감소시켰을 때 코아 자체에 색조를 부여한 Lava Frame Zirconia 군과 KaVo Everest Zirconia 군의 경우 육안으로 인지 가능한 색조의 차이를 보이지 않았으나, 불투명 도재를 도포한 Digident CAD/CAM Zirconia 군의 경우 육안으로 인지 가능한 색조의 차이를 보였다. 결론: 코아 자체에 색조를 부여할 경우 지르코니아 코아 자체의 색을 피개하기 위해 도포하는 불투명 도재층 축성에 필요한 두께를 감소시킬 수 있어 색조 재현에 더욱 유리하며, 치아의 삭제량을 감소시킬 수 있을 것으로 판단되었다.

• 대한치과보철학회지
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• 제43권4호
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• pp.466-477
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• 2005

Statement of problem : Problem of matching the appearance of porcelain restorations with the patient's natural dentition has always been a concern to dental clinicians. Recently, demands for esthetics, even in restorations requiring strength, has brought a revolution to dentistry and increased use of zirconia. Among the various factors, shade and translucency or the core can significantly affect the overall esthetics of the restoration and should be considered when selecting an all-ceramic system. Purpose : The purpose of this study was to spectrophotometrically evaluate the influence of different zirconia systems and core thickness on the final shade of all-ceramic restorations using the CIEL$^*a^*b^*$ system. Material and Methods: Core specimens (n : 20 per group) of In-Ceram Alumina, In-Ceram Zirconia, Digident CAD/CAM Zirconia, Cercon Zirconia were fabricated 20mm in diameter. 10 specimens of each group were fabricated at core thickness of 0.5mm and 0.7mm. These core specimens were veneered with shade Al & A3 porcelain of the recommended manufacturer. CIEL$^*a^*b^*$ coordinates were recorded for each specimen with a spectrophotometer (Model CM-2600d, Minolta, Japan). Color differences were calculated using the equation ${\Delta}E^*=[({\Delta}L^*)^2+({\Delta}a^*)^2+({\Delta}b^*)^2]^{\frac{1}{2}}$. Results : 1. Specimens of core thickness 0.5mm and 0.7mm did not exhibit clinically perceived color difference. 2. Regarding shade reproducibility, In-Ceram Alumina and In-Ceram Zirconia showed significant difference within each group. 3. Cercon Zirconia group showed the highest $L^*$ value and Digident Zirconia group showed lowest $a^*$ & $b^*$ value. 4. Generally the shade difference between materials was higher in the A3 shade group than in the Al shade group. Conclusion: Within the limitations of this study, there was no color difference after increase in core thickness and every all-ceramic system has color characteristics that clinicians have to consider when selecting materials. Also, manufacturers of different porcelain systems must make every effort to achieve color reproducibility.