METHODS: Two kinds of denture resins were used: conventional heat-cured resin and auto-polymerized resin; Kevlar fiber were cut into (0.6±0.1)cm and mixed with polymers at different content of 0.5wt%,2.0w%,3.5wt% and 5.0wt%, respectively. Group of polymers without fibers was set up as control. Specimens in each group were prepared and evaluated according to ISO 1567:1999 for flexural strength, elastic modulus, water sorption and solubility. Scanning electron microscope (SEM) was used to observe the fracture surfaces and adhesion of the Kevlar fiber to the polymethyl methacrylate (PMMA). The values of different resin were summarized and compared among all groups. One-way analysis of variance (ANOVA) was used to determine statistical differences (P<0.05) and the Turkey test was used to determine differences among groups.
RESULTS: Both auto- and heat-polymerized resin reinforced by Kevlar fiber, the flexural strength and elastic modulus were significantly statistical different (p<0.01) from the control when the fiber concentration reached 3.5wt%. SEM observations demonstrated the connective surface between resin matrix and fibers. Water sorption was not statistically different (p>0.05) between fiber-reinforced group and control in either kind of resin. For the solubility, statistic difference existed between the group of 0.5wt% and control under the heat-cured condition (p<0.05), while 5.0wt% group of auto-polymerized resin was obviously different from the controlled group.
CONCLUSION: Both the flexural strength and elastic modulus of heat-polymerized and auto-polymerized denture resin can be enhanced by Kevlar fiber and the strengthen effect was related with fiber percentage. Kevlar fiber had no obvious impact on either water absorption or solubility, but the way of polymerization may influence these two properties.