The effects of various additives on the performance of 2,2＇-bis[4-(methacryloxy-2-hydroxy-propoxy)-phenyl] propane (Bis-GMA)/barium glass powder (Ba) composites were examined. Bis-GMA/Ba composites were manufactured by curing with visible light to measure various mechanical properties. The diametral tensile strengths (DTS) of Bis-GMA/Ba composites were the primary focus of this investigation. The main additives used were trimethylolpropyltrimethacrylate (TMPT), 1,4-bis-(tri-methoxysilylethyl) benzene (BTB), and cationic styryl silane. These additives were applied as both integral blends and aqueous pretreatments. Besides the DTS, Vickers hardness of cured matrix resins and the viscosity of composite pastes were measured to study the properties of the matrix resins and the processibility of the composites, respectively. Integral blends showed similar processibility to aqueous pretreatments. The addition of TMPT to the matrix resins increased Vickers hardness of integral blend systems as a result of its trimethacrylate functional group. BTB was useful in increasing the wet DTS of Bis-GMA/silane-treated Ba composites. STS was effective in improving the performance of Bis-GMA/Ba composites in time cases of both the integral blends and aqueous pretreatments. (C) 2000 John Wiley & Sons, Inc.