Effect of Adherend Characteristics for Bond Strength of Dental Resin Adhesives

Recent resin adhesives had very strong bond strength。However，it is doubtfull in endurance of the bond strength for clinical use。In this study，the following became clear on the above problem.1。Creation of the testing condition for bond strength deterioration by thermal cycling.Desirable temperature of thermal cycling bath are 5°C and 60°C，and the specimens should be keep for 30 seconds in each bath.The adequate number of thermal cycling are 1000 times per day.2。Effects of the thermal expansion coefficient of adherends for the deterioration of bond strength。It will be one of the causes of the deterioration that the strain by thermal cycling resulting from the difference of the thermal expansion coefficient between the adherends and adhesives。But，the assumption are not recognized，because the strain are absorved into the elastic limit of resin adhesives.3。Correlation between the bond strength and rigidity of adherends。The bond strength become very weak by to deform the adherend.It proved the above phenomenon，using the dental alloys and human or bovine tooth with various hardness。In case of alloys，there exists an obvious relation between the hardness and bond strength。The rizing gradient of bond strength for Vickers hardness of enamel is about1.But，the relation in teeth is relatively small，for large deviation in the hardness or stucture.And，the bovine teeth are able to use as substitutes of human teeth in these testing，for the both had a very similar bond strength.4。Comparison the bond strength measured in vivo and in vitro.We directly measured the bond stength in vivo by shear and tensile，using stainless steel lingual botton attached onto the surface of tooth。This values agrees with the results obtained体外.But，the bond strength measured by shear are relatively large compared to the values by tensile。

Recent resin adhesives had very strong bond strength. However, it is doubtfull in endurance of the bond strength for clinical use. In this study, the following became clear on the above problem.1. Creation of the testing condition for bond strength deterioration by thermal cycling. Desirable temperature of thermal cycling bath are 5゜C and 60゜C, and the specimens should be keep for 30 seconds in each bath. The adequate number of thermal cycling are 1000 times per day.2. Effects of the thermal expansion coefficient of adherends for the deterioration of bond strength. It will be one of the causes of the deterioration that the strain by thermal cycling resulting from the difference of the thermal expansion coefficient between the adherends and adhesives. But, the assumption are not recognized, because the strain are absorved into the elastic limit of resin adhesives.3. Correlation between the bond strength and rigidity of adherends. The bond strength become very weak by to deform the adherend. It proved the above phenomenon, using the dental alloys and human or bovine tooth with various hardness. In case of alloys, there exists an obvious relation between the hardness and bond strength. The rizing gradient of bond strength for Vickers hardness of enamel is about 1 .But,the relation in teeth is relatively small,for large deviation in the hardness or stucture. And, the bovine teeth are able to use as substitutes of human teeth in these testing, for the both had a very similar bond strength.4. Comparison the bond strength measured in vivo and in vitro. We directly measured the bond stength in vivo by shear and tensile, using stainless steel lingual botton attached onto the surface of tooth. This values agrees with the results obtained in vitro. But, the bond strength measured by shear are relatively large compared to the values by tensile.