浸水による裏層材の線膨張と強さの変化 Effect of Immersion in Water on Linear Expansion and Strength of Three Base/liner Materials

硬化方式の異なる3種の裏層材(デュアルキュアー型すなわち光硬化型グラスアイオノマー,光重合型すなわち光硬化型グラスアイオノマー類似物,化学重合型すなわち従来型グラスアイオノマー)の硬化初期の特性を把握するため,硬化直後から水中浸漬1週間後までの寸法,重量および曲げ強さの変化を測定した.3種の裏層材はそれぞれ異なった変化を示した.水中浸漬1週間までの寸法と重量変化とは3種共に有意な関係にあった.これは吸水膨張によると想像された.曲げ強さはそれぞれ異なり,硬化方式の違いを示す強さの経時的変化がみられた.この結果から,1日以上水中浸漬されることによる吸水膨張によって,裏層材の硬化時に生じる窩洞辺縁部との間隙を防止したり,硬化が進行することによる物性の安定化が期待された.

The purpose of this study was to characterize three base/liner materials in the initial stage of setting, i.e., dual-cured (light-activated glass ionomer), light-cured (light-activated glass ionomer analogue), and chemically-cured (conventional glass ionomer) materials. Changes in dimension, weight and flexural strength were examined from immediately after setting to the end of one week following immersion in water. The results obtained from these three types of material differed from each other, and showed a statistically significant correlation between changes in dimension and weight. This may be attributed to hygroscopic expansion. They also showed different flexural strength, indicating differences in the polymerization system. From these results, it appeared that marginal gaps following setting would be compensated for by hygroscopic expansion during immersion in water for one day or more. Physical properties would be favourably improved following the setting process which continues to advance during immersion in water.