Effects of the association of high fluoride- and calcium-containing caries-preventive agents with regular or high fluoride toothpaste on enamel: an in vitro study

Abstract

Objectives: The aim of this in vitro study was to compare the caries-preventive effect of various high fluoride- and calcium-containing caries-preventive agents (> 22.000 ppm F^- [ppm]) in adjunct to use of regular (1450 ppm) or high (5000 ppm) fluoride toothpaste on sound as well as demineralized enamel.

Materials and methods: Bovine enamel specimens (n = 276; 5 mm × 3.5 mm × 3 mm) having one sound surface [ST] and one artificial caries lesion [DT] were randomly allocated to 12 groups. Interventions before pH-cycling were no intervention ([SC₁/SC₅]), application of varnishes/solutions containing NaF (22,600 ppm; Duraphat [NaF₁/NaF₅]); NaF + tricalcium phosphate (22,600 ppm; Clinpro White Varnish [TCP₁/TCP₅]); NaF + CPP-ACP (22,600 ppm; MI Varnish [CPP₁/CPP₅]); silver diammine fluoride (35,400 ppm; Cariestop 30%[SDF₁/SDF₅]); and NaF + calcium fluoride (45,200 ppm; Biophat[CaF₁/CaF₅]). During pH-cycling (28 days, 6 × 120 min demineralization/day) half of the specimens in each group were brushed (10 s; 2 × /day) with either 1,450 (NaF; named, e.g., TCP₁) or 5,000 ppm (NaF; e.g., TCP₅) dentifrice slurry. Differences in integrated mineral loss (∆∆Z) and lesion depth (∆LD) were calculated between values after initial demineralization and after pH-cycling using transversal microradiography.

Results: After pH-cycling, SC₁/SC₅ showed significantly increased ∆Z_DT/LD_DT values, indicating further demineralization (p < 0.05; paired t-test). Decreased ∆Z_DT values, indicating non-significant remineralization, could only be observed in CaF₁/CaF₅ (p > 0.05; paired t-test). Additional use of all varnishes/solutions significantly decreased ∆∆Z_DT/∆∆Z_ST and ∆LD_DT/∆LD_ST compared to SC₁/SC₅ (p < 0.05;ANCOVA). Between 1450 and 5000 ppm dentifrices, a significant difference in ∆∆Z_DT/∆∆Z_ST and ∆LD_DT/∆LD_ST could only be observed for SC₁/SC₅ (p < 0.05; ANCOVA).

Conclusion: Under the conditions chosen, all fluoride varnishes/solutions significantly reduced demineralization. Furthermore, a significant dose-response characteristic for fluoride varnishes could be revealed. However, no additional benefit could be observed, when varnishes were combined with high fluoride instead of regular fluoride dentifrices.

Clinical relevance: For children and adolescents with high caries risks varnishes containing more than 22,600 ppm should be further investigated, as they offered higher caries-preventive effects in vitro. Furthermore, there seems to be no difference in the demineralization-inhibitory capacity of fluoride varnishes when used in combination with either standard or highly fluoridated dentifrices.

Keywords: CPP-ACP; Demineralization; Enamel; Fluoride; In vitro; SDF; Varnish; pH-cycling.