Conversion and temperature rise of remineralizing composites reinforced with inert fillers

ObjectivesRemineralizing experimental composites based on amorphous calcium phosphate (ACP) were investigated. The impact of curing time (20 and 40 s), curing depth (1, 2, 3 and 4 mm) and addition of inert fillers (barium glass and silica) on the conversion and temperature rise during curing were examined.MethodsFive ACP-composites and two control composites were prepared based on the light-curable EBPADMA-TEGDMA-HEMA resin. For temperature measurements, a commercial composite was used as an additional control. Conversion was assessed using FT-Raman spectroscopy by comparing the relative change of the band at 1640 cm−1 before and after polymerization. The temperature rise during curing was recorded in real-time using a T-type thermocouple.ResultsAt 1 mm depth, the ACP-composites attained significantly higher conversion (77.8–87.3%) than the control composites based on the same resin (60.5–66.3%). The addition of inert fillers resulted in approximately 5% lower conversion at clinically relevant depths (up to 2 mm) for the curing time of 40 s. Conversion decline through depths depended on the added inert fillers. Conversion values higher than 80% of the maximum conversion were observed for all of the ACP-composites at depths up to 3 mm, when cured for 40 s. Significantly higher total temperature rise for the ACP-composites (11.5–13.1 °C) was measured compared to the control composites (8.6–10.8 °C) and the commercial control (8.7 °C).ConclusionsThe admixture of inert fillers represents a promising strategy for further development of ACP-composites, as it reduced the temperature rise while negligibly impairing the conversion.Clinical significanceHigh conversions of ACP-composites are favorable in terms of mechanical properties and biocompatibility. However, high conversions were accompanied with high temperature rise, which might present a pulpal hazard.