Effect of Heat Treatment on Different Chemical Properties of Regular and Bulk-fill Resin Composites

Objectives: The aim of this study was to determine the influence of heat treatment on the degree of conversion and chemical components of a regular and a bulk fill composite placed in a class-I cavity using Fourier transform infrared spectroscopy (FTIR) and Themogravimetric analysis (TGA).
Methods: Materials were divided in 4 groups according to resin composite classification and heat treatment, G1 – Regular Resin Composite, G2 – Regular Resin Composite Heated, G3 – Bulk Fill Resin Composite, G4 – Bulk Fill Resin Composite Heated. For TGA analysis (SDT Q600, TA Instruments, New Castle, DE. USA), G1 and G3 were analyzed. Eight samples per group (approximately 30 mg. of material) (n=8) were submitted to temperature treatment reaching 70°C and maintained for 5 minutes. Weight loss (%) over time was measured. For FTIR (Spotlight 200i, PerkinElmer Inc., Waltham, MA. USA), G1, G2, G3 and G4 were placed in 6 cylinders each (4 mm diameter x 2.5 mm depth for G1 and G2; 4 mm diameter x 4 mm depth for G3 and G4) and top and bottom surfaces were analyzed before and after light polymerization (48 hours). Data were analyzed using one-way ANOVA and Tukey post-hoc test (p<0.05).
Results: Statistical analysis showed a significant statistical difference in DC% (P < 0.05). G2 showed higher DC than G1, G3 and G4 (p > 0.05). The Bulk Fill Composite (G3) presented greater weight loss % with increasing temperature than the Regular Composite (G1).
Conclusions: The use of pre-heating treatment did affect relevantly the chemical properties of resin composites. Regular composites under heat treatment showed greater DC%, which can present clinical benefits for dental restorations.