Enamel benefits of a new hydroxyapatite containing fluoride toothpaste

Objectives: To evaluate the enamel benefits of a new toothpaste containing hydroxyapatite (HAP) and sodium monofluorophosphate (SMFP). Methods: Salivary pellicle coated sound bovine enamel specimens were cycled six times through either HAP/water slurry or water alone treatments, followed by citric acid (15mM or 50mM, pH 3.8) challenges and saliva. The extent of enamel demineralisation was determined by changes in the enamel surface microhardness (SMH). In a second study, the sound enamel specimens were treated with either water, non-fluoride toothpaste, the HAP/SMFP toothpaste or the HAP/SMFP toothpaste pre-treated with a phosphatase enzyme, followed by a citric acid challenge (50mM, pH 3.8) and saliva. Changes in SMH were determined after six cycles. The reduction in enamel demineralisation by the HAP/SMFP toothpaste was further evaluated in a pH cycling experiment where the acid challenge was 50mM acetic acid (pH 5.0) for 60mins. The remineralisation of sub-surface enamel lesions was measured via changes in SMH following treatment with the HAP/SMFP toothpaste or control toothpastes. In a radiolabelled study, sound and subsurface enamel lesions were treated with Ca-45 labelled HAP toothpaste in an in vitro pH cycling study and the uptake of labelled calcium determined. Results: The HAP water slurry significantly (p<0.05) reduced the enamel demineralisation caused by the citric acid challenges, at both concentrations, compared to the water controls. The HAP/SMFP toothpaste significantly (p<0.05) reduced the enamel demineralisation caused by both citric acid and acetic acid challenges compared to the control treatments. In the remineralisation study, the HAP/SMFP toothpaste significantly (p<0.05) increased the remineralisation of enamel compared to a non-fluoride toothpaste. The radiolabelled HAP toothpaste study demonstrated the uptake of calcium to sound enamel and subsurface enamel lesions. Conclusions: A new HAP/SMFP containing toothpaste significantly (p<0.05) reduced the demineralisation of enamel caused by acid challenges compared to control treatments and significantly (p<0.05) increased the remineralisation of sub-surface enamel lesions compared to a non-fluoride toothpaste. A radiolabelled HAP study has demonstrated that calcium ions from the HAP are available to be involved in enamel remineralisation processes that are relevant to help protection from dental erosion and dental caries in vivo.