title: Effective taper criterion for the full veneer crown preparation in preclinical prosthodontics.
abstract: OBJECTIVE
  Effective taper criteria must define a realistic, measurable goal that the student can visualize and achieve. Six degrees is widely accepted as the taper criterion for the full veneer crown preparation. However, studies show the actual taper of most preparations to be greater than 12 degrees. The purpose of this study was to determine whether 12 degrees is an effective taper criterion for the full veneer crown preparation in preclinical prosthodontics instruction.
  
  
  METHODS
  A group of 191 full veneer crown preparations with 6 degrees as the taper criterion, and a group of 130 full veneer crown preparations with 12 degrees as the taper criterion were evaluated. All preparations were accomplished by preclinical dental students working on typodonts under examination conditions.
  
  
  RESULTS
  The overall mean taper for each group exceeded the targeted criterion. The overall mean taper for the 6 degrees group was 14,490. When 12 degrees was the criterion, the overall mean taper was 15,580. The t test results indicate significant differences (p < .0001) between the targeted criterion and the actual preparation mean taper in all samples except one: the faciolingual measurements in the 12 degrees group. The faciolingual measurement of 12,920 was not statistically significantly different (.0542) from the targeted criterion of 12 degrees.
  
  
  CONCLUSIONS
  The use of a 12 degrees taper criterion did not result in preclinical students achieving the goal of a 12 degrees taper. However, a 12 degrees criterion is more realistic than a 6 degrees criterion for full veneer crown preparations.
authors.affiliation: Department of Prosthodontics, University of Tennessee, Memphis, College of Dentistry 38163, USA.
authors.forename: C T
authors.initials: CT
authors.lastname: Smith
authors.forename: J J
authors.initials: JJ
authors.lastname: Gary
authors.forename: J E
authors.initials: JE
authors.lastname: Conkin
authors.forename: H L
authors.initials: HL
authors.lastname: Franks
mesh_terms: D003442:Crowns; D003801:Dental Veneers; D006801:Humans; D012015:Reference Standards; D019231:Tooth Preparation, Prosthodontic / Q000379:methods*