Effect of Addition Rubber Modified Montmorillonite on Some Properties of Heat Cured Polymethyl Methacrylate Resin

Aims : The goal of this research was to create a composite of rubber modified-montmorillonite (MMT) and heat cured Polymethyl Methacrylate (PMMA) resin to improve some of the mechanical and physical properties of heat cured (PMMA). Subjects and Methods : A total of 120 specimens were made and divided into four groups, (n=30) for each group. Group A, control group made of conventional heat cured PMMA with no reinforcement. Specimens of the other groups were reinforced by the rubber modified MMT composite with different percentages (2%, 4% and 8%) by weight. Group B (2% composite), group C (4% composite) and group D (8% composite). All specimens were evaluated as regard impact strength, transverse strength, water sorption, hardness, and roughness. Results: The results of this study revealed that, impact strength values of acrylic resin denture base were increase after the addition of rubber MMT –composite at any ratio. After addition of 2% rubber MMT-composite the flexure strength was nearly similar to that of control group. While, a significant reduction occurred after adding 4% and 8% composites. Water sorption was significantly increased by the addition of 4% and 8% of rubber –MMT composite ( P < 0.05). There was a significant decrease in the micro hardness after the addition of 4% and 8 % composite, while insignificant decrease occurred with 2% ratio. As regards to surface roughness there was significant increase in the surface roughness values after addition of rubber –MMT composite for all ratios (P < 0.05). Conclusion : The most favorable properties were observed by the addition of 2% rubber –MMT acrylic composite to the heat-cured acrylic resin . However, PMMA denture base material has drawbacks such as insufficient surface hardness, low flexure and impact strength. Clinically, failure of complete or partial denture prosthesis is most