Evaluation of dental restorative composites containing polyhedral oligomeric silsesquioxane methacrylate

Objectives. The aim of this study was to explore novel polymeric dental restorative composites, in which polyhedral oligomeric sitsesquioxane methacrytate monomer (POSS-MA) was used to partially (or completely) replace the commonly used base monomer 2,2'- bis-[4-(methacryloxypropoxy)-phenyl]-propane (Bis-GMA). Methods. The composites were cured (hardened) by photo-initiated free radical polymerization. Mechanical properties (i.e. flexural strength, Young's modulus and diametral tensile strength) of the composites were tested by a universal mechanical testing machine; photopolymerization induced votumetric shrinkage was measured using a mercury dilatometer; and near infrared (NIR) technique was used to study the degree of methacrylate double bond conversion and photopotymerization rate. Results. Small percentage POSS-MA substitution of Bis-GMA (i.e. mass fraction of 10% or Less) in the resin system improved the mechanical properties of the composites; white large amount substitution led to less desirable mechanical properties, lower methacrylate double bond conversion, and slower photopotymerization rate. Statistical examinations showed the maximum flexural strength of the composites occurred when 10% (mass fraction) of Bis-GMA was replaced by POSS-MA, while the highest modulus occurred when the mass fraction of POSS-MA was 2%. Significance. Polymeric dental restorative composites with improved mechanical properties may be designed by judicious choice of monomer (POSS-MA, Bis-GMA and TEGDMA) compositions. (c) 2004 Academy of Dental Materials. Published by Elsevier Ltd. ALL rights reserved.