Effect of pre-heating on hardness, flexural properties and depth of cure of dental two resin composites

Background: It has been observed that preheating dental composites prior to photo-curing improves their handling characteristics and enhances their mechanical properties.
Aim: This study aimed to investigate the effect of three preheating temperatures on hardness, flexural strength and depth of cure of Filtek™ Z250 XT Nano Hybrid and Filtek™ P60 Packable composites.
Materials & Methods: a total of 90 composite specimens were prepared 30 for each temperature and the samples were preheated at 24, 54 and 68 °C. Vickers microhardness, flexure strength/modulus and depth of cure of preheated samples were recorded for both materials. For each test, thirty specimens for each resin composite were prepared and randomly divided in 3 subgroups (10 for each) according to the preheating temperature. Statistical analysis was carried out using One-Way ANOVA.
Results: Increasing the preheating temperature of Filtek™ Z250 XT Nano-hybrid and Filtek™ P60 packable composites significantly increased the Vickers microhardness number, flexure strength and depth of cure. This effect was prominent particularly when the temperature increased from 24 to 54°C. Filtek™ P60 packable composites showed significantly higher Vickers microhardness number, flexure strength/modulus and depth of cure than Filtek™ Z250 XT Nano-hybrid at the tested preheating temperatures.
Conclusion: preheating improved the hardness, flexure properties and depth of cure of tested composites.