<原著>咬合接触面積がIn-Ceram Alumina/Vitadur Alpha陶材積層セラミックス内の応力分布に与える影響 [in Japanese] <ORIGINAL ARTICLE>Influence of Occlusal Contact Area on the Stress Distribution of In-Ceram Alumina/Vitadur Alpha Porcelain Bilayered Ceramics [in Japanese]
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咬合接触面積がIn-Ceram Alumina/Vitadur Alpha陶材積層セラミックス内の応力分布に与える影響を解析した.積層セラミックに300Nの咬合力を負荷した場合について3次元有限要素法を適用し,In-Ceramコア円板の厚さが1.0mm,陶材の厚さが0.3,0.4,0.5mmの場合について検討した.その結果,陶材表面の最大引張り応力は接触半径の増加とともに低下するが,陶材の厚さには依存しなかった.接触半径が0.2mmでは,最大引張り応力は陶材の平均曲げ破壊応力より大きく,Hertzian cone crackが主要な破壊モードであった.接触半径が0.7mmでは最大引張り応力は陶材の破壊応力より小さく,咬合圧下のオールセラミッククラウンの破壊モードは咬合接触面積に依存することを示した.本研究での解析条件では,咬合接触面積は積層セラミックスの応力分布と破壊モードに大きく影響すると結論した.
The object of this study was to analyze the effect of contact area, over which the load was uniformly distributed, on the stress distribution in Vitadur Alpha Porcelain / Glass Infiltrated Alumina Core bilayered ceramics. Three-dimensional finite element models for the bilayered ceramics subjected to a bite load of 300 N were developed. Bilayered structures of porcelain with thicknesses of 0.3, 0.4, and 0.5 mm, and a core thickness of 1.0 mm, were evaluated. Stress analysis demonstrated that the peak value of principal tensile stress, which occurred at the surface of the porcelain, decreased with increasing contact radius, but was independent of the porcelain thickness. For a contact radius of 0.2 mm, the peak value of principal tensile stress was much higher than the mean bending fracture stress of the porcelain. The results indicated that Herztian cone cracking was the domimant fracture mode of bilayered ceramics. For a contact radius was 0.7 mm, however, the peak value of principal tensile stress was much lower than the mean fracture stress of the porcelain. The results showed that the fracture mode of an all ceramic crown under bite load was dependent on the occlusal contact area. For the conditions analyzed in this study, we concluded that contact area had a major influence on the stress distribution and fracture mode of bilyered ceramics.