Fracture force, deflection, and toughness of acrylic denture repairs involving glass fiber reinforcement.

PURPOSE Fractures in acrylic resin dentures occur quite often in the practice of prosthodontics. A durable repairing system for denture base fracture is desired to avoid recurrent fracture. The purpose of this study was to evaluate the fracture force, deflection, and toughness of a heat-polymerized denture base resin repaired with autopolymerized resin alone (C), visible light-polymerizing resin (VLC), or autopolymerizing resin reinforced with unidirectional (Stick) (MA-FS) and woven glass fibers (StickNet) (MA-SN). Another group was repaired with autopolymerized resin after wetting the repair site with methyl methacrylate (MA-MMA) for 180 seconds. A group of intact specimens was used as control. MATERIALS AND METHODS Heat-polymerizing acrylic resin was used to fabricate the specimens. The specimens (10 per group) were sectioned in half, reassembled with a 3-mm butt-joint gap, and repaired. A cavity was included when glass fibers were used. Three-point bending was used to test the repaired site, and data were analyzed with one-way ANOVA and the Tukey's post hoc test (alpha < or = 0.05). RESULTS Fracture force, deflection, and toughness for the repaired groups without reinforcement (MA: 46.7 +/- 8.6 N, 2.6 +/- 0.3 mm, 0.08 +/- 0.001 J; MA-MMA: 41.0 +/- 7.2 N, 2.7 +/- 0.4 mm, 0.07 +/- 0.002 J) were significantly lower (p < 0.05) than the control group (C: 78.6 +/- 9.6 N, 5.9 +/- 0.4 mm, 0.27 +/- 0.003 J). Repair with visible light-polymerizing resin (VLC, 15.0 +/- 4.0 N, 1.2 +/- 0.4 mm, 0.02 +/- 0.0001 J) resulted in significant reduction of mechanical properties (p < 0.05). Reinforcement with glass fibers restored (MA-SN: 75.8 +/- 9.2 N) or increased (MA-FS: 124.4 +/- 12.5 N) the original strength. CONCLUSION The most effective repair method was the use of autopolymerized resin reinforced with unidirectional glass fibers.