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

The aim of this in vitro study was to compare the caries-preventive effect of various high fluoride- and calcium-containing caries-preventive agents (> 22.000ppm F- [ppm]) in adjunct to use of regular (1450ppm) or high (5000ppm) fluoride toothpaste on sound as well as demineralized enamel. Bovine enamel specimens (n = 276; 5mm × 3.5mm × 3mm) 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 (22,600ppm; Duraphat [NaF1/NaF5]); NaF + tricalcium phosphate (22,600ppm; Clinpro White Varnish [TCP1/TCP5]); NaF + CPP-ACP (22,600ppm; MI Varnish [CPP1/CPP5]); silver diammine fluoride (35,400ppm; Cariestop 30%[SDF1/SDF5]); and NaF + calcium fluoride (45,200ppm; Biophat[CaF1/CaF5]). During pH-cycling (28days, 6 × 120min demineralization/day) half of the specimens in each group were brushed (10s; 2 × /day) with either 1,450 (NaF; named, e.g., TCP1) or 5,000ppm (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. After pH-cycling, SC1/SC5 showed significantly increased ∆ZDT/LDDT values, indicating further demineralization (p < 0.05; paired t-test). Decreased ∆ZDT 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 ∆∆ZDT/∆∆ZST and ∆LDDT/∆LDST compared to SC1/SC5 (p < 0.05;ANCOVA). Between 1450 and 5000ppm dentifrices, a significant difference in ∆∆ZDT/∆∆ZST and ∆LDDT/∆LDST could only be observed for SC1/SC5 (p < 0.05; ANCOVA). 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. For children and adolescents with high caries risks varnishes containing more than 22,600ppm 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.