Response of carious enamel to TiF4 varnish treatment under diverse cariogenic activities in situ

Objective: To compare the effect of TiF4 and NaF varnishes on demineralized bovine enamel under different cariogenic activities in situ. Methods: Twenty subjects participated of this in situ study with 3 crossover phases (14 days each), in which they wore palatal appliances containing demineralized bovine enamel samples (8 samples/appliance for phase) treated with TiF4, NaF (all with 2.45% F) or placebo varnish. The samples were subjected to different cariogenic conditions (1. absence of biofilm accumulation and sucrose exposure; 2. presence of biofilm and absence of sucrose exposure; 3. presence of biofilm and 20% sucrose exposure 4x/day; 4. presence of biofilm and 20% sucrose exposure 8x/day). All were exposed to fluoride dentifrice (2x/day). The mineral content and lesion depth were evaluated using transverse microradiography (TMR) and the data were subjected to RM two-way ANOVA/Bonferroni tests (p < 0.05). Results: TiF4 varnish significantly increased the remineralization of artificial carious lesions compared to placebo, regardless of the cariogenic activity. On the other hand, the remineralizing effect of NaF varnish was dependent on the cariogenic activity. For NaF, remineralization happened only in conditions 1 and 3 compared to placebo varnish (p < 0.0001). NaF was unable to prevent further demineralization under biofilm accumulation and sucrose exposure 8x/day (condition 4). In the absence of fluoride treatment, demineralization happened in all conditions, except in the condition 1. Conclusion: Therefore, 4% TiF4 varnish was the only treatment able to improve enamel remineralization regardless of the cariogenic activity, while NaF varnish failed in preventing further demineralization under high cariogenic activity in situ. Clinical significance: 4% TiF4 varnish showed better remineralizing effect compared to NaF varnish, which was seen regardless of the cariogenic activity. This is a promising finding to support the indication of TiF4 in the clinic.