An In-depth Analysis of the Effects of Preheating Three Different Composite Resin Systems at Two Different Temperatures on Their Microhardness

Abstract

Abstract Background: Composite restorations often have inferior physical properties compared to natural enamel and dentin, leading to early failure. Preheating the traditional composite before its placement and curing seems to enhance all its physical characteristics magically. The objective of the current research was to assess the impact of preheating on the surface microhardness of commonly used composite resin materials, specifically FILTEK P60, FILTEK Z250XT, and Tetric-N-Ceram Bulk fill. Materials and Methods: The resin composite tubes were either left at the ambient room temperature (24°C ± 1°C) or preheated in a commercial preheating device to 50°C and 60°C for 40 min. By inserting uncured preheated composite resin into class II Mseio-Occluso-Distal (MOD) cavities with specifications of 2 ± 0.3 mm axial height, 2 ± 0.3 mm pulpal depth, parallel proximal walls with a 3 ± 0.3 mm buccolingual width, 1.5 ± 0.3 mm gingival width, and an occlusal isthmus width equal to one-third of the intercuspal distance from composite resin tubes, a total of 99 class II MOD cavities on premolars were established. Each specimen’s Vicker’s hardness number (VHN) was determined. The gathered information was examined utilizing a two-way ANOVA and Tukey’s post hoc test with a significance threshold of 0.05. Results: When preheated to the temperatures of 50°C and 60°C, a remarkable rise in the mean Vickers hardness numbers (VHNs) of all the resin composites compared to those maintained at the room temperature (P < 0.05) was seen. The mean VHNs at the room temperature for FILTEK P60, FILTEK Z250XT, and Tetric-N-Ceram were 47.27 ± 9.08, 59.63 ± 1.56, and 75.69 ± 0.80, respectively, with a significant variation between all of them (P < 0.05). The mean VHNs were, respectively, 108.45 ± 2.42, 103.45 ± 1.29, and 113.00 ± 4.35 at 50°C, with a significant variation between them all. At 60°C, the mean VHNs were, respectively, 121.09 ± 1.30, 128.00 ± 0.89, and 135.00 ± 2.04, with a significant variation between all of them (P < 0.05). Conclusion: The surface microhardness of all investigated composite resins was greatly increased by preheating, with Tetric N-Ceram Bulk Fill showing the greatest value at a preheating temperature of 60°C.