Solubilization of hydroxyapatite at neutral pH by an anionic ionic exchange resin

Abstract

Sucrose, induced dental plaque has been shown to contain high amounts of lipoteichoic acids, a bacterial anionic polymer with chemical properties similar to ionic exchange resins. The present study describes an in vitro experiment where a commercial resin Amberlite IR 120 was shown to dissolve hydroxyapatite at neutral pH.

The resin binds calcium and the dissociation of the hydroxyapatite Ca₅(PO₄)₃OH → 5Ca⁺⁺ + 3 PO₄^-3 + OH^- is driven to the right as long as the resin takes up calcium. The dissociation of the hydroxyapatite was monitored by electrical conductivity and pH of the aqueous phase. It is suggested that this mechanism may be of some significance in vivo.