In vitro investigation of polyglass and ceromer veneers abrasion related to cobalt-chromium circumferential clasps

The purpose of this study was to investigate in vitro the behaviour of polyglass and ceromer veneers when submitted to insertion and removal of removable partial denture circumferential clasps. Twenty-four veneer crowns (12 made of polyglass and 12 made of ceromer), as well as the respective cobalt-chromium circumferential clasps were made. Using a proper device, the crowns were then submitted to five thousand cycles of clasp insertion and removal. The verification of the force necessary to remove the clasps over the crowns during the experiment and the macroscopic inspection of the crown veneers were used to evaluate the effects of cycling over the test specimens. The force necessary to remove the clasps over the crowns did not change significantly during the cycling. However, all crown veneers showed an abrasion area, noticed by macroscopic evaluation. By these results, one can conclude that veneers made by polyglass and ceromer suffered abrasion by cobalt-chromium clasps insertion and removal, but this abrasion did not influence significantly the force necessary to remove the clasp over the crowns during the experiment.