Degradation of repaired denture base materials in simulated oral fluid

This in vitro study evaluates the degradation of repaired denture bases upo n immersion in a simulated oral fluid. Denture base materials (Luciton 199( R)), after being repaired by Repair Material(R) and Triad(R), using three d ifferent joint surface designs (butt, round and 45 degrees bevel), were imm ersed onto 99.5 vol.% ethanol/water solution (with similar solubility param eter) for various amounts of time (0-72 h). The flexural loads of the six c ombination of groups were measured by the three-point bending tests using a universal testing machine. Acoustic emission (AE) during sample fracturing were processed using the MISTRA 2001 system. The fracture pattern and surf ace details of the interface were examined with a scanning electronic micro scope (SEM). Data were analysed using three-way ANOVA and Tukey LSD tests. SEM micrographs of the fracture interface were used to differentiate the fr acture mode. The flexural loads (2.72+/-0.51 Kgf) of the round joint specim ens were significantly higher (P<0.05) than those (butt: 1.66+/-0.38 Kgf, 4 5 degrees bevel: 1.93+/-0.41 Kgf) of the other two designs. This correspond s to the microscopic examination in which more cohesive failure mode was fo und for the round joint group after storage. The flexural loads (2.54+/-0.3 9 Kgf) of the specimens repaired with Triad(R) were significantly higher (P <0.05) than those (1.59+/-0.40 Kgf) of specimens repaired with Repair Mater ial(R). Significant progressive reduction of the flexural load and/or AE si gnals of the specimens was noted in proportion to the length of time of the immersion in the simulated oral fluid. Mechanical strength of a denture ba se repaired with a round joint design and light-cured material is significa ntly higher after immersion in simulated oral fluid.