Fluoride release from dental cements and composites: A mechanistic study

SummaryObjectivesThe 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.MethodsCommercial materials (n=3) were prepared according to manufacturers' 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.ResultsThe 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.SignificanceAn 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.