PHYSICAL PROPERTIES OF MULTIPLE PREHEATED RESTORATIVE RESIN COMPOSITES FOR CEMENTATION

Abstract

This study evaluated the effects of repeated preheating cycles on the surface hardness and flexural strength of two resin composites: Filtek Z350XT and Filtek Z250. Each syringe was subjected to four preheating conditions: 0, 1, 10, and 20 cycles. In each cycle, resin composites were preheated to 54°C for 15 minutes, refrigerated overnight, and allowed to equilibrate at room temperature for 30 minutes before testing. The Vickers microhardness was measured on the top and bottom surfaces after 24 hours of dry storage, and the three-point bending test was evaluated after 24 hours of deionized water storage. Data were analyzed using a two-way mixed ANOVA (α = 0.05). Commonly, the microhardness value at the top surface seemed unchanged for both resin composites. However, statistical analysis showed that the microhardness of Z350XT increased significantly after 1 and 10 cycles, while Z250 showed a significant increase only after 10 cycles. At 20 cycles, the top-surface microhardness was not significantly different from the control in either material. For bottom-surface microhardness, Z350XT remained comparable to the control across all cycles, whereas Z250 slightly decreased after 20 cycles compared with the control. The flexural strength increased significantly in Z350XT after one preheating cycle, while Z250 was not significantly affected by preheating cycles. In conclusion, repeated preheating up to 20 cycles did not adversely affect the microhardness or flexural strength of either material, except for the bottom-surface microhardness of Z250, which showed a slight decrease at 20 cycles compared with the control group.

Keywords: Repeated, Preheating, Resin composite, Hardness, Flexural strength