Effect of different amounts of 3-methacryloxypropyltrimethoxysilane

Recently, there have been many materials used for denture base such as polymethyl methacrylate (PMMA) resin, modifi ed PMMA resin and nylon1,2). The material most often used to fabricate denture base and denture teeth was PMMA resin. PMMA is the most commonly used material due to its good mechanical and physical properties, compatibility with oral tissue, aesthetics, ease of repair and low cost. However, some problems such as denture fracture2,3) and wear of the denture teeth still exist4-6). In order to overcome these problems, several attempts were made to modify and improve the strength and hardness of the PMMA7-10). These attempts included the addition of fi ller particles such as zirconia8), glass fi ber9) and alumina7,10). Previously, the addition of alumina into PMMA resulted in increase thermal conductivity and hardness7,10). However, the improvement of mechanical properties by blending alumina into PMMA has not been yet confi rmed. By adding 5% alumina into PMMA, Alhareb and Ahmad8) reported the increase in fracture toughness and fl exural modulus but decrease in tensile strengths. Moreover, Ash et al.11) reported the decrease in ultimate strength. In these studies alumina particles were used without silanization resulting in poor interfacial adhesion between polymer and alumina particles. Due to the poor affi nity of surface chemistry between fi ller and resin matrix, modifi cation of fi ller surface is necessary to achieve good bonding between fi ller and resin matrix, which result in the improved strength of materials. One alternative surface modifi cation of fi ller is to use silane coupling agent to improve surface bonding with resin matrix12-13). Tri-methacryloxypropyl trimethoxysilane (MPS) is a dominant silane coupling agent used in dentistry to modify the surface of silica and glass fi ller blended with resin matrix12-14). The silane coupling agent adsorbed on the fi llers creates bi-layer, chemisorbed and physisorbed silane layers15). The chemisorbed silane is absorbed on the surface via covalent bond. The physisorbed layer is a loosely bound layer over the chemisorbed layer by hydrogen bond and van der Waals force among silane coupling molecules. The physical and mechanical properties created by different layer of silane depended on the nature of the silane deposited on the fi ller surfaces; for example, amount of coupling agent, pH, rate of hydrolysis and condensation, and drying condition used in silanization. To date, the amount of MPS, covering silica fi ller in providing optimal mechanical properties of component was quite clarifi ed13,16). However, there are no studies concerning the amount of MPS on alumina fi llers on the fl exural properties and wear resistance of the alumina-reinforced PMMA. Therefore, the purpose of this study was to evaluate the effects of different MPS amounts treated on alumina fi ller particles on the fl exural properties and wear resistance of alumina-reinforced methacrylate denture base. The null hypothesis was that there would be no differences in the fl exural properties and wear resistance of methacrylate denture base materials reinforced with various amounts of MPS on alumina. Effect of different amounts of 3-methacryloxypropyltrimethoxysilane on the fl exural properties and wear resistance of alumina reinforced PMMA