The effect of dental monomers on critical enzymatic processes has recently been identified as a continuing concern because of leaching from cured resin.  Objective: To determine the effect of dental monomers on pancreatic cholesterol esterase (CEase, bovine). Method: Solutions ofBISGMA, and Bisphenol A Diglycidyl Ether (BADGE) were incubated in vitro with Cease at 24EC. CEase activity was measured by a spectrophotometric assay (Vis 410 nm), which determined the rate of hydrolysis of the substrate p-nitrophenylbutyrate. Results: BISGMA and BADGE, increased the velocity of the reaction catalyzed by CEase. The metabolite of these monomers, Bisphenol A bis(2,3-dihydroxypropyl) ether, and a common plasticizer, di-2-ethylhexyl phthalate (DEHP) also increase the velocity of CEase-catalyzed ester hydrolysis. BISGMA at concentrations of 1.5 – 8.0 mM increased the velocity 126-169%. Increasing BISGMA above 8 mM caused no further increase in velocity. BADGE at 7-25 mM increased the velocity 112-205%. The metabolite of BISGMA and BADGE at concentrations of 2.0 – 7.1 mM increased the velocity 103-113% of its value without metabolite. DEHP at concentrations of 0.52 – 4.3 mM increased the velocity 108-187%. On the other hand, Bisphenol A Dimethacrylate (BADM) was a competitive inhibitor of CEase, with a K_i of 3.1 mM. Conclusion: These results point to the importance of evaluating potential leachates for their effect on critical enzymes.. smithrob@umkc.edu