Enzymatic hydrolysis of (di)methacrylates and their polymers.

Di- and monomethacrylates hydrolyze to methacrylic acid and the alcohol part at neutral pH catalyzed by an unspecific esterase (hydrolase) and by enzymes in saliva. The rate constants of the enzymatic hydrolysis of various (di)methacrylates increase in the following order: HPMA less than BISGMA less than LAMA less than DECMA less than TEGDMA less than UEDMA less than DEGDMA. Esterase added to aqueous slurries of various powders made of polymerized BISGMA/TEGDMA-mixtures gave rise to liberation of methacrylic acid, presumably deriving from degradation of those of the dimethacrylates only bonded in the matrix by one end of the molecule. It was estimated that a TEGDMA-polymer will be hydrolyzed faster than a BISGMA-polymer. It is proposed that hydrolases in saliva increase the wear rate of composite resin fillings.