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Conversion and temperature rise of remineralizing composites reinforced with inert fillers

Objectives: Remineralizing 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. Methods: Five 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. Results: At 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). Conclusions: The 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 significance: High 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.

resin composite ; remineralizing composite ; conversion ; temperature ; raman spectroscopy ; amorphous calcium phosphate

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