title: Effects of pH and concentration of citric, malic and lactic acids on enamel, in vitro.
abstract: OBJECTIVE
  Dental erosion associated with soft drink consumption probably results from the contained dietary acids in the formulations. The pH value of any formulation is an important variable in acid erosion but not necessarily the only important factor. The aim of this study was to measure enamel erosion by citric, malic and lactic acids at pH values and acid concentrations representative of a range found in soft drink formulations and to determine the effect of adding calcium to citric acid.
  
  
  METHODS
  Flat ground enamel samples were prepared from unerupted human third molar teeth. Groups of five specimens were placed in citric, malic and lactic acid solutions of different pH and acid concentration for three by 10 min exposures at 35 degrees C. Enamel loss was measured by profilometry. Enamel specimens were also exposed to citric acid solutions containing calcium at different pH values and at the same pH with different concentrations of calcium.
  
  
  RESULTS
  Numerical data and contour plots for each acid showed a similar pattern for increasing erosion with decreasing pH and increasing acid concentration and vice versa for decreasing erosion. Increasing the concentration of calcium in a fixed pH citric acid solution resulted in decreased erosion. This effect was most marked at higher pH.
  
  
  CONCLUSIONS
  This study has shown that under highly controlled conditions the erosion of enamel by solutions of dietary acids is influenced by the interplay of pH, acid concentration and presence of calcium. These variables and in particular the concentration of calcium could be manipulated to produce soft drinks with reduced erosivity to enamel.
authors.affiliation: Division of Restorative Dentistry, Dental School, Bristol, UK.
authors.forename: J A
authors.initials: JA
authors.lastname: Hughes
authors.forename: N X
authors.initials: NX
authors.lastname: West
authors.forename: D M
authors.initials: DM
authors.lastname: Parker
authors.forename: M H
authors.initials: MH
authors.lastname: van den Braak
authors.forename: M
authors.initials: M
authors.lastname: Addy
mesh_terms: D001628:Beverages / Q000009:adverse effects; D002118:Calcium / Q000494:pharmacology; D019343:Citric Acid / Q000494:pharmacology*; D002957:Citrus; D003743:Dental Enamel / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D006801:Humans; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D019344:Lactic Acid / Q000494:pharmacology*; D008293:Malates / Q000494:pharmacology*; D012996:Solutions; D014077:Tooth Erosion / Q000139:chemically induced / Q000517:prevention & control
chemical_list: D008293:Malates; D012996:Solutions; D019343:Citric Acid; D019344:Lactic Acid; C030298:malic acid; D002118:Calcium