Indiana University-Purdue University Indianapolis (IUPUI) / A provisional restoration must fulfill biologic, mechanical, and esthetic requirements. These prostheses should provide comfort, pulp protection, positional stability, occlusal function, hygiene access, esthetics, strength and retention. Methyl-methacrylate acrylic has assumed many appli¬cations in the field of restorative dentistry. However, the material still has deficiencies, such as polymerization shrinkage, pulpal damage associated with exothermic polymerization and susceptibility to fracture. Bis-GMA composites, Bis-acryl composites and visible light-cured urethane dimethacrylate resins have been developed to address these issues. The purpose of this study was to compare the mechanical properties of provisional restorations made from composite resins (Protemp Plus, Luxatemp Solar, Radica, Protemp Crown) to those made of the traditional methacrylate resins (Jet, Snap, High Impact). Six groups of samples, two groups from methacrylate and four groups from composite based materials, were fabricated. Samples from each group were evaluated for microhardness (n=10), flexural strength and flexural modulus (n=20) according to ISO 4049, and fracture toughness (n=20) according to ISO 13586. From each of the six groups, ten samples were tested for flexural strength, flexural modulus and fracture toughness and 5 samples were tested for microhardness. These tests were done after storing at 37°C in a distilled water solution for 7 days followed by thermal cycling (2500 cycles, 5-55°C, 45 s. dwell). Identical sets of samples from each group were used as controls; these were tested after storing for 24 hours in dry conditions. The results were analyzed by two-way ANOVA with material type and aging conditions as the two main variables. Significance level was set at p=0.05. For flexural strength and flexural modules, the higher values were obtained for Radica. Protemp plus (7 days) and Radica (24h) had the highest fracture toughness value. Protemp crown showed the highest surface hardness. The mechanical properties of composite resin were superior.

Indiana University-Purdue University Indianapolis (IUPUI) / Background: A silorane based resin composite, Filtek LS restorative, has been introduced to overcome the polymerization shrinkage of the methacrylate based resin composite. The repair of resin composite may hold clinical advantages. Currently, there is no available information regarding the repair potential of silorane resin composite with either silorane or methacrylate based resin composite. Objectives: The purpose of this study was to compare the repaired microtensile bond strength of aged silorane resin composite using different surface treatments and either silorane or methacrylate based resin composite. Methods: One hundred and eight silorane resin composite blocks (Filtek LS) were fabricated and aged by thermocycling between 8oC and 48oC (5000 cycles). A control (solid resin composite) and four surface treatment groups (no treatment, acid treatment, aluminum oxide sandblasting and diamond bur abrasion) were tested. Each treatment group was randomly divided in half and repaired with either silorane resin composite (LS adhesive) or methacrylate based resin composite (Filtek Z250/Single Bond Plus). Specimens were 12 blocks and 108 beams per group. After 24 hours in 37oC distilled water, microtensile bond strength testing was performed using a non-trimming technique. Fracture surfaces were examined using an optical microscopy (20X) to determine failure mode. Data was analyzed using Weibull-distribution survival analysis. Results: Aluminum oxide sandblasting followed by silorane or methacrylate based resin composite and acid treatment with methacrylate based resin composite provided insignificant differences from the control (p>0.05). All other groups were significantly lower than the control. Failure was primarily adhesive in all groups. Conclusion: Aluminum oxide sandblasting produced comparable microtensile bond strength compared to the cohesive strength of silorane resin composite. After aluminum oxide sandblasting, aged silorane resin composite can be repaired with either silorane resin composite with LS system adhesive or methacrylate based resin composite with methacrylate based dentin adhesive.