Fracture force, deflection at fracture, and toughness of repaired denture resin subjected to microwave polymerization or reinforced with wire or glass fiber

Statement of problem. The ultimate goal of denture repair is to restore the denture's original strength and avoid further fracture. The best materials and methods for repair have not been conclusively determined. Purpose. This study investigated the fracture force, deflection at fracture, and toughness of a heat-polymerized denture base material repaired with heat-polymerized resin, autopolymerized resin alone, or autopolymerized resin with glass fiber or wire reinforcement. Material and methods. Eight groups were evaluated: 6 with autopolymerized resin repairs, 1 with heat-polymerized resin repairs, and a control group of intact specimens. The 6 autopolymerized resin groups included 1 group xvith no reinforcement, 1 treated with microwave irradiation after polymerization, 2 with monolayer or multilayer glass fiber reinforcement, and 2 with round or braided wire reinforcement. Each group consisted of 12 specimens. The experimental specimens were cut, and a 3-mm butt joint gap was repaired as indicated by the group assignment. A 3-point bending test was used to determine the fracture force, deflection at fracture, and toughness of the specimens. The data were analyzed with 1-way analysis of variance and the Tukey post-hoc test (alpha=.05). Results. The fracture force (28.4 to 73.4 N), deflection (1.6 to 3.8 mm), and toughness (0.02 to 0.13 J) values for all repaired groups were significantly lower than those for the control group (82.79 N, 4.4 mm, and 0.16 J, respectively), with one exception: the mean fracture force of specimens reinforced with round wire (102.9 N). Failure mode was always adhesive, meaning that fracture occurred between the denture base and repair resin. Conclusion. Among the repair treatments tested, the most effective was microwave-irradiated, autopolymerized resin reinforced with round wire or monolayer glass fiber ribbon.