Effect of pre-heating on the mechanical properties of silorane -based and methacrylate -based composites

Abstract

the aim of this study was to evaluate the effect of preheating to temperatures 25, 37, and 68 degrees Celsius on the flexural strength, microhardness and the elastic modulus of two different classes of composites. Methods: one methacrylate based composite(Filtek Z250, 3M-ESPE, St. Paul, MN, USA) and a silorane based composite (Filtek Silorane, 3M-ESPE, St. Paul, MN, USA) were used. The materials were preheated to 25, 37, or 68 degrees Celsius and then inserted into different molds, a rectangular mold for flexural strength and a disc shaped one for microhardness. Then they were cured with a visible light cure device ( Demetron A.2, kerr corporation, US). 17 specimens of each composite were made for each temperature and testing protocol. For the flexural strength testing a three point bending test was done using a universal testing machine. For the microhardness testing a Vickers hardness analysis was performed with a 300gr load applied in 10s using a microhardness tester. Results: the results of two-way ANOVA determined that temperature significantly increases the microhardness of both Silorane and Z250. 25 and 37degrees, and 25 and 68 degrees had significantly different microhardness values while 37 and 68 degrees had no statistically significant difference. The same differences existed for elastic modulus, while flexural strength was not significantly changed by preheating. In all the testing protocols it was found that Z250 had higher values than Silorane. Conclusion: In conclusion the microhardness and the elastic modulus were increased after preheating but, it didnEt affect the flexural strength, thus preheating is clinically advantageous.