Evaluation of enamel surface morphology and microhardness after the application of different protective agents

The aim of this in vitro study was to compare the effect of different protective agents on the surface microhardness and morphology on enamel eroded by a cola drink. Sixty sound anterior teeth were randomly divided into five groups. The baseline surface microhardness of the enamel was measured. For demineralization procedures, all teeth were immersed in cola for 8 minutes and surface microhardness was remeasured. The five groups for remineralization procedures were defined as: Group 1: Artificial saliva, Group 2: 1.23% Acidulated Phosphate Fluoride gel (APF), Group 3: 5% NaF varnish, Group 4: Casein Phosphopeptide-Amorphous Calcium Phosphate (CPP-ACP), and Group 5: Probiotic yogurt. After each experimental procedure, a third microhardness measurement was repeated. Surface morphological changes were observed using SEM. All data were recorded for each group and statistically analyzed using two-way analysis of variance and one-way repeated-measures analysis of variance. All tests were performed at a significance level of p < 0.05. No significant differences for baseline microhardness values were found (P> 0.05). The mean surface microhardness in all groups decreased significantly after immersion in cola (P< 0.05). After remineralization, NaF varnish and APF gel significantly increased the surface microhardness values. There were no significant increases in the surface microhardness values of artificial saliva, CPP-ACP and probiotic yogurt. This study concludes that NaF varnish is more effective in re-hardening of eroded enamel.