ABSTRACT: The aim of this study was to evaluate the flexural strength of acrylic resin bars by varying the types of resin polymerization and reinforcement methods. Fourteen groups (N=10) were created by the interaction of factors in study: type of resin (self-cured (SC) or heat-cured (HC)) and reinforcement method (industrialized glass fiber (Ind), unidirectional glass fiber (Uni), short glass fiber (Short), unidirectional and short glass fiber (Uni-Short), thermoplastic resin fiber (Tpl), and steel wire (SW)). Reinforced bars (25×2×2 mm) were tested in flexural strength (0.5 mm/min) and examined by scanning electron microscopy (SEM). Data (MPa) were submitted to factorial analysis, ANOVA, and Tukey and T-student tests (a=5%) showing significant interaction (P=0.008), for SC: Uni (241.71±67.77)a, Uni-Short (221.05±71.97)a, Ind (215.21±46.59)ab, SW (190.51±31.49)abc, Short (156.31±28.76)bcd, Tpl (132.51±20.21)cd, Control SC (101.47±19.79)d and for HC: Ind (268.93±105.65)a, Uni (215.14±67.60)ab, Short (198.44±95.27)abc, Uni-Short (189.56±92.27)abc, Tpl (161.32±62.51)cd, SW (106.69±28.70)cd, and Control HC (93.39±39.61)d. SEM analysis showed better fiber-resin interaction for HC. Nonimpregnated fibers, irrespective of their length, tend to improve fracture strength of acrylics.
