Impact of Fluoride and Radiation on Thermal Stability of Teeth

Objectives: The aim of this study was to determine the effect of radiation and silver diamine fluoride (SDF) treatment on the thermal stability of dentin and enamel.
Methods: Forty human posterior teeth were divided into two groups (N=20): control (no treatment) and SDF-treated. Both groups were exposed to 2 grays of daily radiation for six weeks using an X-Rad 320ix biological irradiator. Enamel and dentin were pulverized using a SPEX freezer mill (Thermo-Fisher Scientific, Norristown PA). Differential scanning calorimetry (DSC) was performed using a NETZSCH instrument. Samples were heated from room temperature to 1429 °C. Dentin and enamel samples were pooled.
Results: Results of DSC included energy absorbed and released. SDF-treated dentin had the lowest energy absorbed (198.9 mW/mg), followed by radiated dentin (199.1 mW/mg), control dentin (224.3 mW/mg), and radiated-and SDF-treated dentin (279.8 mW/mg). The radiated enamel also absorbed more energy (211.3 mW/mg) than the SDF-treated enamel (135.3 mW/mg). However, for enamel, the control group absorbed the lowest energy (133.4 mW/mg).

The radiated-and SDF-treated dentin released more energy (1626.4 mW/mg) compared to the SDF-treated dentin (1281.3 mW/mg), radiated dentin (1195.5 mW/mg), and control dentin (1147.7 mW/mg). The radiated enamel released much more energy (634.8 mW/mg) than both the control (72.1 mW/mg) and SFD-treated (47.4 mW/mg) enamel. Across all dentin and enamel groups, the control dentin (286.6 °C) and SDF-treated enamel (323.2 °C) had the largest heat reversal temperature.
Conclusions: Effects of radiation and SDF treatment on thermal behavior differ for enamel and dentin. Dentin control absorbed more heat than SDF-and radiation-treated dentin. Both radiation and SDF treatment increased the thermal stability of dentin. SDF treatment also increases the thermal stability of enamel. Compared to dentin, enamel has a low content of combustible material.