STUDY ON STRESS INDUCED CORROSION AND LIFETIME OF DENTAL RESIN

本研究旨在阐明影响义齿基托热固化树脂裂纹扩展的因素。在恒载条件下，对引入预裂的三点弯曲试件的裂纹扩展进行了测量，探讨了环境溶液及其浓度对其裂纹扩展的影响。此外，通过测量载荷变化与裂纹扩展的关系、观察动态三点弯曲试验时试样侧面出现的裂纹以及用扫描电镜观察断口表面，研究了裂纹与开裂在环境溶液存在下促进裂纹扩展的关系。结果表明，乙醇和乙酸对裂纹扩展有显著的促进作用，且其作用随浓度的增加而增强。说明义齿基托树脂在同时受到咬合应力和环境溶液（如酒精饮料和醋碟）的作用下，更容易引发裂纹扩展。动态试验和扫描电镜观察结果表明，裂纹在开始扩展之前就产生了裂纹。这些结果表明，义齿基托的裂纹扩展首先是在咬应力作用下产生裂纹，其次是环境条件下允许裂纹的生长。

This study has been made to clarify the factors affecting a crack growth of denture base heat cured resin. The crack growth of three point bending specimen introduced the precrack was measured at the constant load to investigate the effects of environmental solutions and its concentrations. Furthermore, the relations between crack and craze promoted the crack growth in the presence of environmental solution have been examined by measuring the relationship between load change and crack growth, by observing the crack appeared on the side surface of specimen during the dynamic three point bending test, and by observing the fracture surface using SEM. As a result, the ethanol and acetic acid promoted the crack growth remarkably, and its effect increased with increasing the concentration. This fact indicated that the denture base resin which received both bite stress and environmental solutions such as alcoholic drink and vinegard dish would initiate the crack growth easily. The experimental results of dynamic test and SEM observation showed that the craze was created before the crack started to grow. These results suggested that the crack growth of denture base was proceeded from the craze creation under the bite stress in the first place, and the environmental solution allowed to grow to crack in the second place.