title: An in vitro assessment of tooth preparation for porcelain veneer restorations.
abstract: OBJECTIVE
  This in vitro study aimed to examine the depth of preparation and incidence of dentine exposure resulting from the use of a 'freehand' technique to prepare maxillary central incisors for porcelain veneers.
  
  
  METHODS
  Twenty-two maxillary central incisors were selected. Prior to preparation an index of the labial surface of each tooth was recorded and the tooth secured in a jig to permit accurate relocation. Two operators each prepared 11 teeth aiming to reduce the labial thickness evenly by 0.5 mm. Low viscosity silicone impression material was then placed on the index and the teeth relocated into the jig. Upon removal, this material was sectioned in the cervical, middle and incisal thirds of the tooth and its thickness measured using a toolmaker's microscope. The teeth were acid etched and also stained with a dentine dye to identify any area of dentine exposed during preparation.
  
  
  RESULTS
  Significant differences (P < 0.001) in the depth of preparation at different sites, with least reduction in the mid-incisal region, were found. Greater reduction was found at the cervical and proximal margins with areas of dentine exposed at those sites in the majority of teeth.
  
  
  CONCLUSIONS
  In view of the incidence and position of dentine exposure found in this study, the use of a dentine bonding system during the placement of porcelain veneers would appear essential when employing a 'freehand' preparation technique.
authors.affiliation: Department of Restorative Dentistry, Leeds Dental Institute, UK.
authors.forename: B R
authors.initials: BR
authors.lastname: Nattress
authors.forename: C C
authors.initials: CC
authors.lastname: Youngson
authors.forename: C J
authors.initials: CJ
authors.lastname: Patterson
authors.forename: D M
authors.initials: DM
authors.lastname: Martin
authors.forename: J P
authors.initials: JP
authors.lastname: Ralph
mesh_terms: D003737:Dental Cavity Preparation / Q000009:adverse effects / Q000379:methods*; D003761:Dental Impression Technique; D003763:Dental Leakage / Q000209:etiology / Q000517:prevention & control; D003776:Dental Porcelain; D003801:Dental Veneers; D003804:Dentin; D017220:Dentin-Bonding Agents; D006801:Humans; D007180:Incisor
chemical_list: D017220:Dentin-Bonding Agents; D003776:Dental Porcelain