The effect of clinically relevant thermocycling on the flexural properties of endodontic post materials

Objectives: It is suggested that fibre-reinforced composite (FRC) posts have lower elastic moduli than metal posts and this will reduce the incidence of root fracture. However, the mechanical properties may be altered in the oral environment. The aims of this study were to determine the effect on the flexural properties of FRC and metal post materials produced by: (1) a thermocycling regime which was clinically relevant and representative of that which wouldoccur during 1 year in the mouth and (2)storage for 1 year at body temperature. Methods: Nine FRC and two metal post material samples were sealed in polythene sleeves and thermocycled between 10 8C and 50 8C for 10,000 cycles. Additional samples were stored dry at 37 8C for 1 year. The flexural strength and moduli were determined by three-point bending and compared with untreated control samples. Results: Thermocycling and storage at 37 8C for 1 year decreased the mean flexural modulus of all materials. This was statistically significant for 8 of 11 materials after thermocycling, and 4 of 11 materials after storage at 37 8 C( p < 0.05). Thermocycling and storage at 37 8C produced a non-significant increase in yield strength for both metal post materials. Thermocycling significantly increased the flexural strength of Postec while it decreased for the other FRC materials. Storage at 37 8C increased the flexural strength of three FRC materials (significantly for Postec) while it was decreased among the other materials.