title: Human enamel erosion in constant composition citric acid solutions as a function of degree of saturation with respect to hydroxyapatite.
abstract: The objective of this study was to investigate human enamel erosion under constant composition conditions, as a function of solution degree of saturation (DS) with respect to hydroxyapatite. The experimental conditions were relevant to the initial stages of enamel erosion by soft drinks. Nanoindentation was used to compare enamel surface softening caused by a control mineral water and two citric acid solutions with DS = 0.000 and DS = 0.032, both having pH 3.30. Enamel hardness and reduced elastic modulus were measured after 0, 30, 60, 120, 300 and 600 s exposure. A statistically significant change in enamel hardness was detected after 30 s exposure to both citric acid solutions, indicating that nanoindentation is extremely sensitive to the initial stages of erosion. There was a statistically significant difference between the mechanical properties of enamel exposed to the two citric acid solutions after 30, 60 and 120 s. At these times, the solution with DS = 0.000 caused twice as much enamel softening as that with DS = 0.032. This demonstrates that it may be possible to design a soft drink with a low erosive potential and a good taste by a small change in DS, at a typical drink pH.
authors.affiliation: Department of Oral and Dental Science, University of Bristol, Bristol, UK.
authors.forename: M E
authors.initials: ME
authors.lastname: Barbour
authors.forename: D M
authors.initials: DM
authors.lastname: Parker
authors.forename: G C
authors.initials: GC
authors.lastname: Allen
authors.forename: K D
authors.initials: KD
authors.lastname: Jandt
mesh_terms: D001628:Beverages / Q000009:adverse effects; D002118:Calcium / Q000494:pharmacology; D019343:Citric Acid / Q000494:pharmacology*; D003743:Dental Enamel / Q000187:drug effects; D003747:Dental Enamel Solubility / Q000187:drug effects*; D004548:Elasticity; D006244:Hardness / Q000187:drug effects; D006245:Hardness Tests / Q000379:methods; D006801:Humans; D006863:Hydrogen-Ion Concentration; D006882:Hydroxyapatites / Q000494:pharmacology*; D010710:Phosphates / Q000494:pharmacology; D014077:Tooth Erosion / Q000139:chemically induced*
chemical_list: D006882:Hydroxyapatites; D010710:Phosphates; D019343:Citric Acid; D002118:Calcium