プレス成形可能な二ケイ酸リチウムガラスセラミックスの曲げ強度に及ぼす結晶方位の影響

Effect of crystal orientation on flexural strength of pressable lithium disilicate glass-ceramics.

抄録

本研究では、4種類のプレス用二ケイ酸リチウムガラスセラミックスの結晶方位を調べ、曲げ強度に及ぼす結晶方位の影響を評価した。棒状（長さ24mm、厚さ1.2mm、幅4.0mm）、円盤状（直径12mm、厚さ0.5mm）、および歯冠状（上顎第一大臼歯）の試験片をメーカーの指示に従って作製した。棒状と円盤状の試験片について、3点曲げ強さと2軸曲げ強さを測定した。X線回折法と走査型電子顕微鏡を用いて微細構造解析を行った。三点曲げ強さは、棒状試験片の長手方向に平行な結晶方位によって改善された。二次元結晶方位と二軸曲げ強さには関係がなかった。本研究の結果は，二軸曲げ強さが断面方向の結晶方位によって改善されると仮定した．プレス修復物は、その結晶方位により、粉砕修復物よりも高い強度を有することが予想される。

This study examined the crystal orientation of four kinds of pressable lithium disilicate glass-ceramics and evaluated the effect of crystal orientation on flexural strength. Bar-shaped (24 mm in length, 1.2 mm in thickness, 4.0 mm in width), disk-shaped (12 mm in diameter, 0.5 mm in thickness), and crown-shaped (maxillary first molar) specimens were prepared according to the manufacturer's instructions. Three-point and biaxial flexural strengths were measured for bar- and disk-shaped specimens. Microstructure analysis was performed using X-ray diffractometry and scanning electron microscopy. Three-point flexural strength was improved by parallel crystal orientation along the longitudinal direction of the bar-shaped specimen. There was no relationship between two-dimensional crystal orientation and biaxial flexural strength. The results of this study assumed that biaxial flexural strength was improved by the crystal orientation in the cross-sectional direction. Pressed restorations are expected to possess higher strength than milled restorations due to their crystal orientation.