Microcapsule Chemical Structure Effect on Phosphate Release from Varnish Formulations

Objectives: The objective of this study was to determine the effect of chemical structure of the microcapsule on the release of phosphate ions from microcapsules with ion permeable membranes formulated in resin and rosin based varnish formulations.  Methods: A heterogeneous polymerization technique was utilized to prepare microcapsules containing an aqueous solution of 2.4 M potassium phosphate dibasic made with either a microcapsule based on an ethylene glycol polyurethane structure or a butanediol based polyurethane structure.  Fifteen weight percent of microcapsules were formulated into both a resin and rosin based varnish formulation for a total of four formulations.  Ion release profiles were studied as a function of microcapsule chemical structure and time for 12 weeks. Phosphate ion detection was performed by the molybdenum blue method and reported as ppm of phosphate ion released per gram of formulation.    Results:   Ion release profiles were studied as a function of microcapsule chemical structure in the varnish formulations.  A table highlighting some of the results is shown below.

Continuous Phase	Ion Release Measured	Initial Conc in microcapsule (M)	Weight % of microcapsules	Microcapsule Structure	1 day (ppm)	1 week (ppm)	6 weeks (ppm)	12 weeks (ppm)
Rosin	Phosphate	2.4	15	EG	46	70	227	350
Rosin	Phosphate	2.4	15	BD	53	102	343	478
Resin	Phosphate	2.4	15	EG	26	119	178	192
Resin	Phosphate	2.4	15	BD	19	81	155	174

Conclusions: Ion release profiles were generated for varnish formulations containing microencapsulated aqueous solutions that contained biologically available phosphate ions useful in remineralization.  The preparation of varnish formulations with controlled release profiles appears promising based on the variation of chemical of the microcapsule fillers.  This work is funded in part by Premier Dental Products Incorporated, GL Materials Research LLC and an NSF University-Industry Partnership grant.