title: Effect of time on the remineralisation of enamel by synthetic saliva after citric acid erosion.
abstract: The aim of this in vitro study was to determine the influence of remineralisation time on rehardening of surface-softened enamel after citric acid erosion. Seven groups of 13 samples of human enamel were eroded in 0.3% citric acid at pH 3.2 for 2 h followed by profilometric measurements. Individual groups of specimens were placed in artificial saliva for 1, 2, 4, 6, 9 or 24 h. A control group was placed in isotonic saline for 24 h. After new profilometric measurements samples were ultrasonicated stepwise up to 480 s with profilometric measurements performed at 5, 30, 120, 240 and 480 s to measure the depth of surface softening. The control group had a softened surface layer of mean thickness 2.9 microm. Mineral deposition was seen at all remineralisation times by scanning electron microscopy. Exposure to artificial saliva for 1, 2 or 4 h produced a partial rehardening of the softened enamel; the additional surface losses produced by ultrasonication were lower and time delayed compared to the control group. Specimens remineralised for 6, 9 and 24 h showed little evidence of surface loss after ultrasonication. The data suggest that a complete rehardening of the softened enamel in vitro is reached after a remineralisation time of 6 h. These data are of clinical relevance to tooth wear. However, there is a need for studies in situ of enamel demineralisation and remineralisation.
authors.affiliation: Department of Prosthetic Dentistry, Medical University of Hannover, Germany; (b)Division of Restorative Dentistry, Dental School, Bristol, UK. M.Eisenburger@gmx.de
authors.forename: M
authors.initials: M
authors.lastname: Eisenburger
authors.forename: M
authors.initials: M
authors.lastname: Addy
authors.forename: J A
authors.initials: JA
authors.lastname: Hughes
authors.forename: R P
authors.initials: RP
authors.lastname: Shellis
mesh_terms: D000704:Analysis of Variance; D019343:Citric Acid / Q000494:pharmacology; D003743:Dental Enamel / Q000187:drug effects; D006244:Hardness; D006801:Humans; D008855:Microscopy, Electron, Scanning; D008963:Molar; D012464:Saliva, Artificial / Q000627:therapeutic use*; D013010:Sonication; D018709:Statistics, Nonparametric; D013499:Surface Properties; D013997:Time Factors; D014077:Tooth Erosion / Q000139:chemically induced / Q000628:therapy*; D014089:Tooth Remineralization / Q000379:methods*
chemical_list: D012464:Saliva, Artificial; D019343:Citric Acid