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.