Effects of Carboxymethyl Cellulose-Based Saliva Substitutes with Varying Degrees of Saturation with Respect to Calcium Phosphates on Artificial Enamel Lesions

Abstract

The aim of the present study was to evaluate the effects of experimental saliva substitutes based on carboxymethyl cellulose (CMC) differing in degrees of saturation with respect to calcium phosphates on the mineral loss of enamel in vitro. Demineralized bovine specimens (subsurface lesions) were exposed to one of six experimental CMC-based solutions with theoretical degrees of saturation with respect to octacalcium phosphate (S_OCP) of S0, S0.5, S1, S2, S4, and S8 for 10 weeks. A previously studied saliva substitute (Glandosane) and two aqueous solutions (C0 and C1) served as controls. Mineral losses and lesion depths before and after storage were evaluated from microradiographs. Free and bound calcium as well as phosphate and fluoride concentrations were determined. According to these measurements, S_OCP of S2, S4, and S8 was 0.3, 1.1, and 3.4, respectively. Storage in Glandosane and both negative controls resulted in significant demineralization (p < 0.05). Only S2 significantly remineralized the specimens (p < 0.05). All other solutions showed neutral effects. No significant differences in mineralization between S0 and C0 as well as between S1 and C1 could be observed (p > 0.05). It can be concluded that a CMC-based solution actually unsaturated with respect to octacalcium phosphate (S2) shows most pronounced remineralization capability under the conditions chosen. This might be explained by a more favorable balance between calcium bound to CMC in an adsorbed layer at the enamel-liquid interface and heterogeneous nucleation of calcium phosphates within a solution compared to solutions either supersaturated or having lower levels of saturation.