Fluoride Dose-Response and Anticaries Effect of Herbal Antibacterial Agents and (Nano-)Hydroxyapatite on Dentin...

The aim of the study was to investigate the caries-preventive effect of fluoride-free toothpastes, containing either herbal agents or (nano-)hydroxyapatite.

Bovine dentin specimens each having a sound (ST) and a demineralized area (DT) were prepared and randomly allocated to eleven groups (n = 187). Treatments during pH cycling (28 days; 6 × 120 min demineralization/day) were brushing 2×/day with 0 ppm F- [NaF₀], 500 ppm F- [NaF₅₀₀], 1,100 ppm F- [NaF₁₁₀₀], grape seed extract [GSE], (nano-)hydroxyapatite, melaleuca oil [MO₁, MO₂, MO-CU], and propolis + myrrh [PM₁, PM₂] containing dentifrices. Dentifrice slurries were prepared with deionized water (1:3 w/w). Differences in integrated mineral loss (∆∆Z) and lesion depth (∆LD) were evaluated before and after pH cycling using transversal microradiography.

The correlation between ΔΔZ/ΔLD and F- concentration (NaF₀, NaF₅₀₀, NaF₁₁₀₀) was strong for the DT (r_{ΔΔZ, DT} = 0.681; p < 0.001) and very strong for ST (r_{ΔΔZ, ST} = 0.861; p < 0.001), indicating a fluoride dose-response for both baseline substrate conditions. For ΔΔZ_DT and ΔLD_DT, only NaF₁₁₀₀ and GSE revealed significant differences compared with NaF₀ (p < 0.001; ANOVA). For ΔΔZ_ST and ΔLD_ST, significant differences could be found for NaF₁₁₀₀ and NaF₅₀₀ compared to all fluoride-free groups (p ≤ 0.002; ANOVA), without significant difference between fluoride-free groups (p = 1.000; ANOVA). For DT and ST, a hypermineralized surface layer and no surface loss could only be observed when fluoride was present.

A dose-response for fluoride concentrations was observed in this mild demineralization pH-cycling model. Fluoride-free dentifrices containing GSE or melaleuca oil showed certain preventive effect against further progression of root caries lesions. However, surface loss was observed for all fluoride-free dentifrices.