Analysis of the degradation of dental composite materials by mass spectrometry and nanoindentation

Most dental composites consist of a polymerizable resin matrix bound to glass filler particles by silane coupling agents. The resin in these composites includes bisphenol A diglycidyl methacrylate as well as other resins and organic components. Silane coupling agents such as 3-(trimethoxysilyl) propyl methacrylate are typically used to improve the mechanical properties of the dental composites by forming a covalent bond between the glass filler particles and the resin.;Dental composite materials are subjected to severe chemical, microbiological, and mechanical conditions due to the oral environment. Degradation studies of commercial dental composites are severely limited by their chemical complexity. Degradation of dental composites was previously examined using a simplified overlayer model in which bisphenol A diglycidyl methacrylate was covalently bound to a porous silicon oxide surface. This model captures the essential chemical characteristics of the filler particle-silane-resin interface. This model system consists of the resin matrix compound Bis-GMA covalently bound via a methacryloyl overlayer to amorphous silicon oxide surface via a siloxane bond.;For this thesis, the overlayer model and bulk dental composites were aged in water and with oral bacterial biofilms to test how they degraded using these different aging media. The material properties were also tested by nanoindentation to determine the effect that aging has on bulk dental composites with and without the use of silanated filler particles.