Resins in Restorative Dental Materials: Reactor Response

¹ Dental Material Science and Laboratory, Universitätsklinik und Poliklinik für Zahn-, Mund- und Kieferkrankheiten, Universität Hamburg, West Germany

The response stresses two remarks of Prof. Braden about the sensitizing agents and the importance of a decrease of shrinkage in new dental resins.

The objective of our own investigation was to measure the wear of veneering resins brushed with dentifrices and to find a good combination of resin and fillers, as well as which abrasives in toothpastes make the smallest abrasion on veneering resins. The in vitro method — described in this paper— is based on the results obtained in an in vivo abrasion test with dental students. The in vitro abrasion test instrument has to produce similar results with the six tested dentifrices on polymethylmethacrylate as measured in our in vivo test. Two different series of veneering resins were tested, one with increasing cross-linkage, the other with increasing microfiller. In the series with increasing cross-linkage, the hardness increased and the abrasion values decreased. In the series with increasing microfiller, the hardness also increased; however, the abrasion resistance was not related to the hardness. Two dentifrices caused nearly no abrasion, while three higher-abrasive dentifrices showed an increase of abrasion on the 40% and 60% filler-containing specimens. Thus, the abrasion resistance can be improved with the right relation between microfiller and cross-linkage. A toothbrush with medium stiffness and a dentifrice containing an amorphous silica, i. e., Syloblanc 7/ 82, should be recommended for appropriate oral hygiene when veneering resins are present.

The objective of our second study was to use a torsion test to investigate the bond strength between metal and resin. The results depend on the cross-head speed used, i. e., the stress results increased with the speed.