Pattern of the Effect of Fluoride Varnishes On Early Caries

Objective: Application of varnish with high fluoride concentration on early caries lesion has been hypothesized to promote the formation of poorly permeable remineralized surface, thereby hindering the remineralization of the underlying subsurface demineralization. This study aimed to histologically and quantitatively demonstrate the remineralization pattern of varying fluoride concentrations within an early caries lesion. Method: Early caries lesions created on extracted human teeth were cut out as enamel block, and each block was used to construct an in situ appliance; following removal of an enamel slice (control slice) from each block. Each of 30 human volunteers wore 4 appliances in 4 randomized crossover phases. During each phase (8 weeks period), the lesions received either of 4 treatment modalities; application of varnish with (A) high (5% NaF), (B) low (0.2% NaF), (C) without (0% NaF) fluoride or (D) lesion exposure to saliva-alone. Following treatment, an enamel slice was cut from each block (test slice). The control and test slices were processed using transverse microradiography (TMR) to quantify pre-test and post-test lesion parameters of mineral loss (Dz) and lesion depth (LD). Result: Microradiographs showed mineral deposition to be evenly distributed within the surface and subsurface layers of the lesion with all treatment modalities. No lesion was completely remineralized in all groups within 8 weeks. Paired t-tests (a=0.05, n=30) showed significant difference in pre-test and post-test Dz with A(p=0.001), B(p=0.002) and D(p=0.006), but not with C. Duncan multiple comparisons indicated no significant difference in the amount mineral gained with A, B, C and D. Reduction in LD was only significant with A and B, but not with C and D. Conclusion: This study demonstrated that mineral deposition was evenly distributed within an early caries lesion during remineralization with fluoride varnish of high or low fluoride concentration. Supported by NIH/NIDCR R21DE015590.