The effect of length parameter on the repair strength of acrylic resin using fibers or metal wires.

Fractures of acrylic resin dentures occur quite often in prosthodontic practice. Autopolymerized acrylic resin is the most popular material for denture repair; however, it is significantly weaker than the intact heat-polymerized resin. Metal strengtheners or fibers have been used to reinforce the resin. This study investigated the fracture force, deflection, and toughness of a heat-polymerized denture resin that had been repaired either with autopolymerized resin alone or with autopolymerized resin that had been reinforced with metal wire or woven glass fibers. This study also investigated how these qualities were affected when the length of the strengthener was reduced. Sixty specimens were divided into six groups of ten (depending on the repair method), together with a control group of intact heat-polymerized resin specimens. The group repaired with autopolymerized resin alone reported significantly lower (p < 0.05) fracture force, deflection at fracture, and toughness when compared to the control. When metal wire or glass fiber at full or half-length was used for reinforcement, only the original fracture force was restored; deflection and toughness remained significantly lower (p < 0.05). Based on this study, it appears that the group reinforced with full lengths of metal wire offered the best potential for reinforcement.

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.