Toughening Of PMMA Denture Base Materials Through Copolymerization

Denture base materials require high strength, including flexural strength and impact strength, to resist the effect of complex forces in the oral cavity. On the other hand, it is requested that materials exhibit small deformation under forces. At present PMMA has been widely applied to various prosthetic replacement operations. However, the mechanical properties of PMMA can not sufficiently meet the requirements of prosthetic replacement. Even though PMMA denture base materials have optimal choice of clinical experience and indication, the arrangement of false teeth, and the most reasonable operation process, they still have problems on mechanical properties, especially the low impact strength, which frequently causes the breakage of denture base materials and dysbacteriosis that can cause denture stomatitis. Therefore, how to improve the toughness and the mechanical properties becomes the research focus.In this paper, three copolymers were prepared via in situ suspension copolymerization using butyl acrylate (BA), butyl methacrylate (BMA), or methyl acrylate (MA) with MMA, respectively. Fourier transform infrared spectroscopy (FT-IR) and Nuclear magnetic resonance (13C-NMR) were used to investigate the interaction between MMA and the other three monomers. The influence of the three monomers on molecular weight of PMMA, the size and shape of copolymer microsphere, the mechanical, thermal properties, absorbing value, dissolution value and residual monomer content were investigated.The results indicate that, PMMA copolymers could be successfully prepared via in situ suspension copolymerization by controlling the reaction conditions. The presence and small content of different monomers slightly influenced the molecular weight of PMMA and the size and shape of copolymer microsphere. The presence of BA, BMA and MA could improve mechanical and thermal properties, especially the impact strength of PMMA. The toughness was remarkably improved. Compared with pure PMMA, the absorbing value, dissolution value and residual monomer content were obviously improved.