Effect of Acrylic Resin Processing Variables on Biaxial Flexural Strength

Objective: To assess the effect of denture resin type, packing and processing methods on the biaxial flexural strength (BFS) of poly methyl methacrylate (PMMA). Methods: Veined and plain PMMA was used to produce discs of 12mm diameter and 2mm thickness. Discs were produced using conventional (two part flask) or an injection packing system, and was processed using a dry heat or water bath curing method. Eight combinations of resin type, packing and processing method were used with ten discs per combination. After processing, de-vesting, trimming and polishing the discs were stored for 50 hrs at 37°C in accordance with International standard BS,BM,ISO 1567:2001. BFS testing was then carried out using a tensile test machine. Results: No statistically significant differences were seen between any of the eight combinations tested (p>0.05). However, the veined material gave higher BFS results than the plain material. The injection packing method gave higher BFS results than the conventional method and the dry heat processing method gave higher BFS results than the water bath. Conclusions: Although not statistically significant, veined PMMA, injection packed and dry heat processed would produce dentures that had a higher resistance to fracture than those produced using plain PMMA, conventionally packed and processed in a water bath.