Fluoride release from dental cements and composites: A mechanistic study

Objectives The purpose of this study was (1) to compare the fluoride release profile of an experimental composite to commercial GICs, resin-modified GICs, and composite resins; (2) to assess the fluoride release process. Methods Commercial materials (n=3) were prepared according to manufacturersʹ directions. The experimental composite (n=3) consisted of 78 wt% filler and 22 wt% resin. The resin consisted of 19 wt% BisGMA, 38 wt% UDMA, 19 wt% TEGDMA, and 24 wt% HEMA. Disc specimens were placed into 25 ml of deionized water in sealed polyethylene vials and shaked at 1.4 Hz at 37 °C. Fluoride release was measured using a fluoride-ion specific electrode at different time intervals up to 284 days. Results The fluoride release rate of the experimental composite demonstrated the highest rate of release within the first day (p=0.05), but decreased significantly by day 7. Release rates of the commercial glass-ionomer cements and resin-modified glass-ionomer cements thereafter were significantly higher than the experimental and commercial composites at p=0.05. Among the materials studied, cumulative fluoride release is adequately described by a two-term equation consisting of an initial fluoride release via a rapid dissolution process followed by a long-term diffusive release. Significance An increase in the hydrophilicity of the polymer matrix through the introduction of HEMA improved the fluoride release over the short term during which dissolution occurs. Such a release behavior could be beneficial if it results in a fluoride reservoir that could be maintained by a prolonged slower release thereafter.