合着用セメントの操作変動とその影響 : 第 1 報 練和時間の違いによる硬化時間ならびに被膜厚さの変化

Abstract

The characteristics of the luting cements are affected by the mixing procedures such as powder/liquid ratio, mixing condition and/or mixing time. In the present report, the effects of the mixing time on the setting time and film thickness were examined. The setting time was evaluated by the time counted from the end of mix to the final set which seemed to be practically usefull for estimating the workability and was referred to as the practical setting time, instead of the standardized setting time counted from the start of mix. The setting time and film thickness were variously affected by the mixing time even within the instruction of the manufacturer in the zinc phosphate cements, probably depending on the respective interactions between reaction rate, forming rate of reaction product and mixing time. The polycarboxylate cements showed no or only a small increase in the setting time with increase in the mixing time up to 75 sec. The film thickness was significantly smaller than those of other types of cements and little affected by the mixing time. The glass ionomer cements were also found to be less affected by the mixing time although some products showed markedly smaller film thickness when mixed for the minimum time of their manufacturers' instruction.