Objective: The objective of this study was to evaluate the diametral tensile strength (DTS) and Knoop hardness (KH) of direct (Filtek Z350-3M/ESPE and Charisma-Heraeus Kulzer) and indirect composites (Sinfony-3M/ESPE and Signum-Heraeus Kulzer) kept in storage for two periods of time, 24 hours and 10 months, in distilled water.
Methods: Twenty-five specimens of each material were prepared. DTS (n=10) was tested using a universal testing machine (Versat, model 2000) at a crosshead speed of 1.0 mm/min. KH (n=5) was measured using Knoop micro-hardness (HMV-2000; 50 gf for 15 s). All tests were performed 24 hours after polymerization and after 10 months of storage in distilled water at 37°C. The data were statistically analyzed using Kolmogorov-Smirnov, ANOVA and t-Student (P=.05).
Results: Filtek Z350, Sinfony, and Signum showed higher DTS values than Charisma after 24 hours. After storage, Sinfony and Signum showed higher DTS values because the storage did not influence the DTS values of the indirect composites. Filtek Z350 showed higher KH values after 24 hours and after storage than other composites; the storage influenced the KH of all composites except Sinfony.
Conclusion: Storage for 10 months did not influence the properties of the indirect composite Sinfony. In general, the indirect composites showed higher DTS values than direct composites, especially after 10 months storage. The direct composite Filtek Z350 obtained the highest KH values regardless of storage.
Keywords: Composite resin; dental materials; hardness.