Enamel Remineralization by Dental Varnishes Correlates with F Uptake

Objectives: To evaluate enamel subsurface lesion fluoride uptake and remineralization by fluoride dental varnishes.
Methods: MI varnish containing casein phosphopeptide - amorphous calcium phosphate (CPP-ACP) with 2.26% (w/w) fluoride, and Duraphat varnish containing 2.26% (w/w) fluoride (no added calcium) were selected for analysis compared with placebo varnish (no added calcium or fluoride). Enamel subsurface lesions were prepared in enamel obtained from extracted human third molars. The slabs were randomized to three groups (n=10) and cut into half-slabs with one half stored as a control, the other half used as the test half-slab with varnishes applied to the lesion windows. The test half-slabs were then individually immersed in an artificial saliva (AS) pH 7.0 for 14 days at 37 °C. Each treated half-slab was then matched with its corresponding control half-slab for sectioning and mineral content analysis using transverse microradiography. Calcium, phosphate and fluoride ions in the AS after treatment were analyzed using ion chromatography. Enamel subsurface lesions were analyzed for fluoride uptake using electron probe microanalysis. The data were statistically analyzed using a linear mixed model with SPSS Version 22 (SPSS Inc, Chicago, USA).
Results: The fluoride-containing varnishes significantly promoted remineralization of enamel subsurface lesions when compared with the placebo varnish (2.82±2.07%R). MI varnish, containing fluoride and CPP-ACP, was superior (41.15±7.80%R) to the fluoride-alone varnish (18.46±2.34%R) in promoting remineralization. MI varnish, in addition to a higher level release of calcium, phosphate and fluoride ions, also produced significantly greater enamel lesion fluoride uptake (0.441±0.083 wt%) compared with Duraphat (0.249±0.038 wt%) and the placebo varnish (0.062±0.052 wt%). There was a very close correlation (p < 0.0001) between the level of remineralization (%R) and enamel lesion fluoride uptake (F wt%).
Conclusions: MI varnish containing fluoride and CPP-ACP was superior to the varnish contained fluoride alone in promoting enamel lesion remineralization and F uptake.