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.
Highlights
Heat- or self-polymerized acrylic resins are generally composed of polymethyl methacrylate (PMMA)
For the SP groups the control was similar to Thermoplastic resin (Tpl) and Short, and for the HP groups the control was similar to Steel wire (SW) and Tpl
For the SP groups the highest reinforcement effect was presented by Unidirectional glass fiber (Uni) but was similar to Uni-Short, SW, and Industrialized glass fiber (Ind)
Summary
Heat- or self-polymerized acrylic resins are generally composed of polymethyl methacrylate (PMMA). They are used for complete dentures, provisional restorations, or even aesthetic surgery corrections [1, 2]. PMMA has a relatively low flexural strength [3] and can undergo failure as a result of occlusal disharmonies, overload, fatigue, and impacts caused by accidents [4]. In order to strengthen PMMA, several methods have been proposed. The use of metal and fiber reinforcements produces beneficial results [5,6,7]. Metal wires can be placed inside polymers, but fibers have been demonstrated to be more effective [5]. Metal and glass fiber exhibit different mechanical properties
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