Purpose: The objective of this study was to measure the release of biologically available ions from microcapsules with ion permeable membranes. Methods: A heterogeneous polymerization technique was utilized to prepare microcapsules containing either an aqueous solution of potassium phosphate dibasic or an aqueous solution of calcium nitrate or an aqueous solution of sodium fluoride. Six different polyurethane based microcapsule shells were prepared and characterized based on ethylene glycol, butanediol, hexanediol, octanediol, triethylene gylcol and bisphenol A structural units. Ion release profiles were studied as a function of initial ion concentration within the microcapsule, ion type and microcapsule structure. Phosphate ion detection was performed by the molybdenum blue method. Calcium and fluoride ion release measurements were performed using ion specific electrodes. Results: Ion release profiles were studied as a function of initial ion concentration in the microcapsule, chemical structure and ion type resulted in a complex relationship between these variables. A table highlighting some of the results is shown below.
Microcapsule Structure | Ion Release Measured | Initial Concentration in microcapsule (M) | 0.1 hour (ppm) | 20 hours (1 ppm) | 60 hours (1 ppm) | 100 hours (1 ppm) |
Ethylene glycol | Calcium | 1 | <1 | 4 | 55 | 142 |
Ethylene Glycol | Phosphate | 1 | <1 | 12 | 72 | 108 |
Octanediol | Phophate | 1 | <1 | 3 | 5 | 17 |
Ethylene Glycol | Phosphate | 3 | 4 | 173 | 950 | 1980 |
Conclusions: Ion release profiles were generated for microencapsulated aqueous solutions that contained biologically available ions useful in remineralization. The preparation of microcapsules with controlled release profiles appears promising based on microcapsule structure and initial ion concentration. This work is funded in part by Premier Dental Products Incorporated.