The control of phosphate ion release from ion permeable microcapsules formulated into rosin varnish and resin glaze

Objectives: The occurrence of recurrent caries at the interface of dental materials and the enamel surface is an important performance issue. The objective of this study was to investigate the most effective way to control the release rate of bioavailable phosphate ions contained in aqueous solutions within ion permeable microcapsules formulated into rosin based varnishes and resin based sealants, in order to promote remineralization.

Methods: Microcapsules that contained aqueous solutions of K2HPO4 with concentrations from 0.8 to 7.4M were prepared. 3-50w/w% of microcapsules were loaded into both rosin and resin based dental formulations.

Results: The effect of initial salt solution concentration inside the microcapsules and weight percent loading of the microcapsules on release rate were contrasted. The effect of microcapsule loading was found to be highly dependent on the continuous phase. In rosin, 3-15w/w% loading resulted in rapid release of ions. Higher weight percent loadings were initially slower but resulted in sustained release of ions. In resin, 3-15w/w% formulations slowly released ions for at least 300 days, while higher loading formulations released an initial burst of ions. Initial salt solution concentration contained inside the microcapsule affected ion release rate. Initial rate of ion release was greatest at a concentration that was less than the maximum concentration studied in both continuous phases.

Significance: Phosphate ion release can be controlled from resin or rosin based dental material by adjusting initial salt solution concentration in microcapsules or percent loading of microcapsules. The potential for burst release from a varnish or slow, sustained release from a sealant has been demonstrated.