Effect of lesion characteristics and mineralizing solution type on enamel remineralization in vitro

The aim was to study the effect of lesion preparation technique and solution composition on remineralization of artificial lesions in vitro. Lesions were prepared with similar total mineral loss, but different mineral distribution, i.e., low (14.0) or high R (34.8) values. Lesions from both groups were remineralized (10 days, 37 degrees C) in two different solutions, with similar supersaturation with respect to hydroxyapatite (St), but calcium:phosphate ratios representing either hydroxyapatite stoichiometry or plaque fluid (PF). Remineralization was quantified microradiographically, mineral distribution was compared with natural white-spot lesions. Mineral loss and depth decreased significantly, and surface-zone mineral content (Zmax) increased significantly, in all lesions. Overall there was a significant relationship of decreasing remineralization with increasing Zmax, but not within either lesion type. PF was significantly more efficient than St in high-R lesions, with lesions remineralizing almost completely in PF. Remineralization was not significantly different in PF or St for low-R lesions but in high-R lesions, PF was more efficient than St, possibly through differences in relative saturations with respect to different calcium phosphates. Differences in area:solution ratios and baseline Zmax values may also have explained the different response to PF. Low-R lesions were similar to natural white-spot lesions in terms of mineral distribution, whereas high-R were not. Concluding, both lesion and remineralizing solution type had a marked influence on remineralization. It is proposed that use of low-R lesions would be more appropriate where more physiologically relevant mineral distribution is required, whereas high-R lesions would be appropriate for studying inherent remineralizing efficiency.