Novel CaF 2 Nanocomposite with High Strength and Fluoride Ion Release

Secondary caries and restoration fracture remain common problems in dentistry. This study tested the hypothesis that combining nano-CaF₂ and glass fillers would yield nanocomposites with high mechanical properties and F release. Novel CaF₂ nanoparticles (56-nm) were synthesized via spray-drying and incorporated into resin. F release increased with increasing the nano-CaF₂ content, or with decreasing pH (p < 0.05). F-release rates at 70-84 days were 1.13 µg/(cm²·day) and 0.50 µg/(cm²·day) for nanocomposites containing 30% and 20% nano-CaF₂, respectively. They matched the 0.65 µg/(cm²·day) of resin-modified glass ionomer (p > 0.1). The nanocomposites had flexural strengths of 70-120 MPa, after 84-day immersion at pH 4, pH 5.5, and pH 7. These strengths were nearly three-fold that of resin-modified glass ionomer, and matched/exceeded a composite with little F release. In summary, novel CaF₂ nanoparticles produced high F release at low filler levels, thereby making room in resin for reinforcement glass. This yielded nanocomposites with high F-release and stress-bearing properties, which may help reduce secondary caries and restoration fracture.