title: Enamel thickness after preparation of tooth for porcelain laminate.
abstract: OBJECTIVE
  In this investigation the thickness of enamel in the gingival, middle, and incisal thirds of the labial surface of the anterior teeth were measured regarding preparation of the teeth for porcelain laminate veneers.
  
  
  METHODS
  Part one, 20 extracted intact human maxillary central and lateral incisors ten of each were selected. The teeth were imbedded in autopolimerize acrylic resin. Cross section was preformed through the midline of the incisal, middle and cervical one-third of the labial surface of the teeth. The samples were observed under reflected stereomicroscope and the thickness of enamel was recorded. Part II, the effect of different types of preparation on dentin exposure was evaluated. Thirty maxillary central incisor teeth were randomly divided into two groups: A: Knife-edge preparation. B: Chamfer preparation. All samples were embedded in autopolimerize acrylic resin using a silicon mold. The samples were cut through the midline of the teeth. The surface of the samples were polished and enamel and dentin were observed under the stereomicroscope.
  
  
  RESULTS
  Data were analyzed by ANOVA-one way test. The results of this study showed that the least enamel thickness in the central incisor was 345 and in lateral incisor is 235 μ this thickness is related to the one-third labial cervical area. Maximum thickness in maxillary central and lateral incisors in the one-third labial incisal surface was 1260 μ and 1220μ, respectively. In the second part of the study, the tendency of dentinal exposure was shown with the chamfer preparation, but no dentinal exposure was found in the knife-edge preparation. The differences between groups were significant (p<0.05).
  
  
  CONCLUSIONS
  The knowledge of enamel thickness in different part of labial surface is very important. The thickness of enamel in the gingival area does not permit a chamfer preparation. The knife edge preparation is preferable in gingival area.
authors.affiliation: Associate Professor, Dental Research Center Dentistry Research Institute, Department of Operative Dentistry, School of Dentistry, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Ayoub
authors.initials: A
authors.lastname: Pahlevan
authors.affiliation: Assistant Professor, Dental Research Center Dentistry Research Institute, Department of Operative Dentistry, School of Dentistry, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Mansoreh
authors.initials: M
authors.lastname: Mirzaee
authors.affiliation: Professor, Dental Research Center Dentistry Research Institute, Department of Operative Dentistry, School of Dentistry, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Esmaeil
authors.initials: E
authors.lastname: Yassine
authors.affiliation: Assistant Professor, Dental Research Center Dentistry Research Institute, Department of Operative Dentistry, School of Dentistry, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Ladan
authors.initials: L
authors.lastname: Ranjbar Omrany
authors.affiliation: Associate Professor, Dental Research Center Dentistry Research Institute, Department of Operative Dentistry, School of Dentistry, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Masumeh
authors.initials: M
authors.lastname: Hasani Tabatabaee
authors.affiliation: Associate Professor, Dental Research Center Dentistry Research Institute, Department of Operative Dentistry, School of Dentistry, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Hamid
authors.initials: H
authors.lastname: Kermanshah
authors.affiliation: Assistant Professor, Dental Research Center Dentistry Research Institute, Department of Operative Dentistry, School of Dentistry, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Sakineh
authors.initials: S
authors.lastname: Arami
authors.affiliation: Assistant Professor, Dental Research Center Dentistry Research Institute, Department of Operative Dentistry, School of Dentistry, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Mehdy
authors.initials: M
authors.lastname: Abbasi
keywords: Chamfer; Knife Edge; Laminate; Porcelain; Thickness