Enzymatic degradation of BISGMA/TEGDMA-polymers causing decreased microhardness and greater wear in vitro.

The microhardness of the surfaces of BISGMA/TEGDMA-polymers decreased after treatment with pork liver esterase for 48 h in concentrations greater than or equal to 0.05 U/ml. This softening effect on BISGMA/TEGDMA-polymer surfaces was also shown as an increased wear rate of the polymers in the presence of esterase measured by a laboratory abrasion method. In this method, polymer cylinders were vigorously shaken in an aqueous slurry containing abrasive particles. The shaking was performed for 3 s followed by a rest period of either 100 or 200 s. This was repeated for 24 h. A greater mean loss of weight of the cylinders was measured when esterase was present in the slurry and the loss of weight increased significantly from 6.7% to 23.8% (P less than 0.001) when the rest period was increased from 100 s to 200 s. The results indicate that enzymatic hydrolytic activity in the mouth will contribute to a breakdown of composite resin fillings.