title: Effect of low pH on surface rehardening efficacy of high concentration fluoride treatments on non-cavitated lesions.
abstract: OBJECTIVE
  Professionally applied acidulated phosphate fluoride has been shown to reduce caries incidence. However, it has been suggested that its efficacy might be reduced in advanced non-cavitated lesions. This study aimed to compare the surface rehardening and fluoride uptake effect of 2%-NaF solutions at different pH on non-cavitated caries-like lesions with two different levels of demineralization.
  
  
  METHODS
  Human enamel specimens were demineralized to create early and advanced non-cavitated lesions. Specimens for each type of lesion were divided into 3 groups, treated for four minutes with either 2%-NaF pH 3.5, 2%-NaF at pH 7.0, or neutral deionized water, and exposed to a pH cycling remineralization/demineralization model for five days. An additional treatment was then done as described above followed by five more days of cycling (total of 2 treatments, ten-day pH cycling). Specimens were analyzed for surface microhardness change and fluoride uptake.
  
  
  RESULTS
  It was found that for both types of lesions, acidic pH fluoride treatment was significantly (p<0.05) more effective than neutral pH treatment in rehardening the lesion surface and promoting fluoride uptake. Furthermore, the low pH vs neutral pH difference in rehardening was significantly larger in the less demineralized lesions (p=0.0001). Water treatment resulted in no rehardening or fluoride uptake.
  
  
  CONCLUSIONS
  Results from this study suggest that high concentration fluoride treatments at acidic pH are more effective in rehardening the surface of non-cavitated caries lesions and promoting fluoride uptake than those at neutral pH. This effect appears to be greater in less demineralized lesions when compared to more advanced ones.
  
  
  CONCLUSIONS
  The results of this investigation suggest that when no other attenuating circumstances are present (e.g., the possibility of damaging tooth-coloured restorations), high concentration fluoride treatments for high risk individuals might be more efficacious using products at low pH.
authors.affiliation: University of Michigan School of Dentistry, Ann Arbor, MI, USA. carlosgc@umich.edu
authors.forename: C
authors.initials: C
authors.lastname: González-Cabezas
authors.forename: H
authors.initials: H
authors.lastname: Jiang
authors.forename: M
authors.initials: M
authors.lastname: Fontana
authors.forename: G
authors.initials: G
authors.lastname: Eckert
mesh_terms: D002327:Cariostatic Agents / Q000008:administration & dosage* / Q000493:pharmacokinetics; D003743:Dental Enamel / Q000187:drug effects* / Q000378:metabolism; D044622:Dental Pellicle / Q000737:chemistry; D006244:Hardness; D006801:Humans; D006863:Hydrogen-Ion Concentration; D019344:Lactic Acid / Q000009:adverse effects; D008422:Materials Testing; D012464:Saliva, Artificial / Q000737:chemistry; D012969:Sodium Fluoride / Q000008:administration & dosage* / Q000493:pharmacokinetics; D013997:Time Factors; D017001:Tooth Demineralization / Q000145:classification / Q000188:drug therapy* / Q000378:metabolism; D014089:Tooth Remineralization; D014867:Water
chemical_list: D002327:Cariostatic Agents; D012464:Saliva, Artificial; D014867:Water; D019344:Lactic Acid; D012969:Sodium Fluoride