title: Effect of pH on Galla chinensis extract's stability and anti-caries properties in vitro.
abstract: OBJECTIVE
  Considering that Galla chinensis extract (GCE) solution has a low pH, which might dissolve dental enamel, we investigated the effects of elevation of pH on GCE stability, and on its anti-caries properties.
  
  
  METHODS
  Stability of GCE solutions, either in H(2)O (pH less than 4.0) or when buffered at pH 5.5, 7.0 and 10.0, was assessed from UV-VIS spectra. Inhibition of enamel demineralization was determined in a pH-cycling set up, comprising treatments with either GCE solutions or negative control buffers and acid and neutral buffer immersions. Demineralization was assessed by calcium in the acetate buffers. To determine antimicrobial properties, polymicrobial biofilms were formed after saliva inoculation on glass surfaces which were treated after 48 h. Treatment output parameters were lactic acid formation and viability, the latter by colony forming unit (CFU) counts.
  
  
  RESULTS
  At pH 7.0 and higher GCE solutions changed colour and absorption spectra in UV-VIS, indicative of chemical changes. Regarding enamel demineralization, significant inhibitions (P<0.05) were found for all GCE treatments when compared with corresponding controls. In polymicrobial biofilms, GCE reduced the acid production, compared with the negative controls (P<0.05). However, this difference was only significant at the lower pH values.
  
  
  CONCLUSIONS
  GCE solutions were unstable under neutral and alkaline conditions. pH did not significantly influence the inhibiting effect of GCE on enamel demineralization. However, GCE was not effective on polymicrobial biofilms at alkaline pH (8.5). To avoid enamel damage due to acidic treatment, GCE solutions should be used at about pH 5.5.
authors.affiliation: State Key Laboratory of Oral Diseases, Sichuan University, Chengdu, China.
authors.forename: Xuelian
authors.initials: X
authors.lastname: Huang
authors.forename: Lei
authors.initials: L
authors.lastname: Cheng
authors.forename: R A M
authors.initials: RA
authors.lastname: Exterkate
authors.forename: Mingdong
authors.initials: M
authors.lastname: Liu
authors.forename: Xuedong
authors.initials: X
authors.lastname: Zhou
authors.forename: Jiyao
authors.initials: J
authors.lastname: Li
authors.forename: J M
authors.initials: JM
authors.lastname: ten Cate
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D018441:Biofilms; D002327:Cariostatic Agents / Q000737:chemistry / Q000494:pharmacology*; D002417:Cattle; D003731:Dental Caries / Q000517:prevention & control*; D003743:Dental Enamel / Q000187:drug effects*; D003747:Dental Enamel Solubility / Q000187:drug effects*; D004355:Drug Stability; D004365:Drugs, Chinese Herbal / Q000737:chemistry / Q000494:pharmacology*; D005707:Gallic Acid / Q000737:chemistry / Q000494:pharmacology*; D006244:Hardness; D006863:Hydrogen-Ion Concentration; D010636:Phenols / Q000737:chemistry; D010936:Plant Extracts / Q000737:chemistry / Q000494:pharmacology*; D029045:Rhus; D013056:Spectrophotometry, Ultraviolet; D013634:Tannins / Q000737:chemistry; D017001:Tooth Demineralization / Q000517:prevention & control*
chemical_list: D002327:Cariostatic Agents; D004365:Drugs, Chinese Herbal; D010636:Phenols; D010936:Plant Extracts; D013634:Tannins; D005707:Gallic Acid