Denture Base Resin: Improvement of Mechanical Properties

Since the 1930s, PMMA has been used as the most popular denture base material. However, its mechanical properties are still far from ideal. Previous studies showed that the optimal processing conditions for PMMA is: 1.2.5:1 Powder/ liquid ratio, 2. Plain type of resin, 3.Conventional packing method and 4.water bath curing for 2hours at 95ºC. OBJECTIVES: The aim of this study is to improve the fracture resistance of PMMA denture bases by: 1. Incorporation of filler particles into PMMA, 2.Chemically modification of matrix resin by silicon fluid addition. MATERIALS & METHODS: I. Tio2, Zro2, Glass Flakes, HDPE (surface-activated high density polyethylene), UHMWPE (surface activated Ultra high molecular weight polyethylene), and PMMA - Silica nanocomposite, were mixed with plain PMMA powder. II Silicone Fluid (Polydimethylsiloxane) was added to resin, 20% by volume of monomer a) before mixing b) while mixing and c) after mixing the monomer with the powder. The mixtures were processed as previously mentioned. Normal PMMA discs were prepared and soaked for 7 days in Silicone Fluid at 37ºC. Biaxial Flexural Strength (BFS), microindentation Fracture Toughness and Vickers Hardness tests were carried out on the samples. Analysis of data was carried out using ONE-WAY ANOVA and TUKEY'S. RESULTS: the addition of Tio2, Zro2 and Glass flakes particles had no significant effect on BFS but did improve fracture toughness and hardness of PMMA. CONCLUSION: Tio2, Zro2 and Glass flake particles improved FT of denture base resin,and Zro2 and Glass flake particles improved PMMA hardness.