Influence of calcium phosphates added to mucin-based saliva substitutes on bovine dentin

Objectives: Remineralization of dentin by mucin-containing saliva substitutes might be inhibited by sialic acids bound to mucin, which are known to complex calcium. Thus, the aim of this investigation was to evaluate the effects of various mucin-containing solutions, differing in calcium phosphate concentrations, to be used as saliva substitutes on demineralized bovine dentin in vitro. Method and Materials: Bovine specimens (153) were embedded in epoxy resin, polished (4,000 grit), and partly covered with nail varnish (control of sound dentin). After demineralization for 14 days (pH 5.5), the specimens (n = 9) were exposed to 14 mucin-based solutions (30 g/L) at 2 different pH values (5.5 or 6.5) and differing in saturation with respect to apatites. Two fluoride-free solutions and the commercially available saliva substitute Saliva Orthana (Orthana, Kastrup) served as controls. Differences in mineral loss (DDZ) and lesion depth (DLD) between the values prior to and after storage in the various solutions were evaluated from microradiographs of thin sections (100 µm). Results: The general linear model revealed an almost significant dependency on calcium for DDZ (P = .050) and a significant dependency on calcium for DLD (P = .037). pH influenced DDZ significantly (P .001), whereas DLD was not influenced significantly (P = .169). Neither DDZ (P = .475) nor DLD (P = .703) were influenced significantly by phosphate. Conclusion: Even with low concentrations of calcium and phosphates, mucin-based saliva substitutes are capable of inhibiting demineralization of bovine dentin, whereas with solutions supersaturated with respect to apatites, a remineralizing effect could be observed. Keywords: calcium, dentin, mucin, phosphates, saliva substitute, solubility