title: AFM study of citric acid-ferric chloride etching characteristics of dentin.
abstract: OBJECTIVE
  To determine the etching characteristics of 10% citric acid etchant with 3% ferric chloride (10-3) compared with related etchants without ferric chloride (10-0), or one of similar pH (36% citric acid).
  
  
  METHODS
  Atomic force microscopy (AFM) was used to measure the surface recession and morphology of dentin. AFM images were taken of the same samples at seven steps of an etching and drying procedure using 10-3 (pH = 1.09), 10-0 (pH = 1.87) or 36% (pH = 1.08) citric acid solutions: at baseline, after etching 15 s, after 5-s air-drying, after rewetting, after 24-hr desiccation, after 30 s rewetting and after 24 hrs rewetting in filtered and purified water.
  
  
  RESULTS
  10-3 etched surfaces receded more than either 10-0 or 36% etched surfaces, and underwent greater collapse on 5-s air-drying. On rewetting all surfaces re-expanded to near their as-etched level. Following prolonged desiccation (24 hrs) all samples collapsed to the level seen after brief air-drying. 30-s rewetting did not restore the surface, but re-expansion of the collapsed collagen matrix was seen at 24 hrs.
authors.affiliation: Department of Restorative Dentistry, University of California San Francisco 94143-0758, USA. graymar@itsa.ucsf.edu
authors.forename: G W
authors.initials: GW
authors.lastname: Marshall
authors.forename: K
authors.initials: K
authors.lastname: Saeki
authors.forename: S A
authors.initials: SA
authors.lastname: Gansky
authors.forename: S J
authors.initials: SJ
authors.lastname: Marshall
mesh_terms: D000134:Acid Etching, Dental; D002712:Chlorides; D019343:Citric Acid / Q000494:pharmacology; D003804:Dentin / Q000187:drug effects*; D005290:Ferric Compounds / Q000494:pharmacology; D006801:Humans; D006863:Hydrogen-Ion Concentration; D018625:Microscopy, Atomic Force; D018709:Statistics, Nonparametric; D013499:Surface Properties / Q000187:drug effects
chemical_list: D002712:Chlorides; D005290:Ferric Compounds; D019343:Citric Acid; C024555:ferric chloride