Filler reinforced acrylic denture base material. Part 2- Effect of water sorption on dimensional changes and transverse strength


Background: PMMA considered the most commonly used for complete dentures. It absorbs a small amount of water which exerts significant effect on its properties. Effect of water on dimensional changes and transverse strength of filler reinforced PMMA were investigated in this study.Materials and methods: Different types of fillers were used: Kevlar (6%), glass fibers (5%) by weight in mat and unidirectional forms, zirconium oxide particles (5%) were used, which was added to acrylic resin. The dimensional changes: after processing, drying, and immersion in water for one month were measured. Transverse strength was measured for three periods (after deflasking, after two days, and after one month in water).Results: least dimensional changes was observed in samples with Kevlar unidirectional, they cause about 75.18% reduction in shrinkage, while with glass unidirectional cause 48.33%. A significant reduction in shrinkage was observed with Kevlar and glass reinforced samples in mat form. The addition of Kevlar unidirectional into acrylic resin caused an increase in transverse strength of about (18.5%) after deflasking, and (14%) after one month in water, the decrease in strength in this group after one month in water was about 12.9% when compared to that after deflasking. The transverse strength of samples with zirconia results in slight decreased in strength but was non significant.Conclusion: The presence of fibers decreases the dimensional changes, and fiber form had an effect on it. The transverse strength of PMMA was increased by the presence of fibers. The strength decreased with water immersion, but fiber reinforced samples remain of higher strength.