title: Effect of preparation convergence on retention and seating discrepancy of complete veneer crowns.
abstract: The purpose of this study was to evaluate the retention and marginal seating discrepancy of complete veneer crown cemented with zinc phosphate cement using various preparation convergence designs. The method employed was that of cementing cast metal crowns onto 46 metal dies fabricated as complete veneer crown preparations with various convergence angles ranging from 0 degrees to 70 degrees and a shoulder finish line. The marginal discrepancy was calculated by measuring the change in crown height before and after cementation using an optical measuring microscope. The force required to remove the crowns from the dies in a vertical direction was determined using an Instron universal testing machine and recorded as retention. The increase in preparation convergence exhibited a wide variation of seating discrepancy between specimens, ranging from 4.58 +/- 1.13 to 73.13 +/- 78.32 microm. Significant tilting of crown was observed as the convergence angle of preparation increased. The retention values ranged from 4.03 +/- 0.61 to 12.12 +/- 0.33 MPa. The Pearson analysis revealed statistically significant correlations between preparation convergence and marginal discrepancy (r = +0.62), and retention (r = -0.91). Crown retention and marginal discrepancy were influenced by the preparation convergence design.
authors.affiliation: Department of Oral Rehabilitation, Medical College of Georgia, GA, USA.
authors.forename: D C N
authors.initials: DC
authors.lastname: Chan
authors.forename: A H
authors.initials: AH
authors.lastname: Wilson
authors.forename: P
authors.initials: P
authors.lastname: Barbe
authors.forename: R J
authors.initials: RJ
authors.lastname: Cronin
authors.forename: C
authors.initials: C
authors.lastname: Chung
authors.forename: K
authors.initials: K
authors.lastname: Chung
mesh_terms: D002484:Cementation / Q000379:methods; D003442:Crowns; D017268:Dental Prosthesis Retention; D019232:Dental Restoration Failure; D003801:Dental Veneers; D006801:Humans; D008422:Materials Testing / Q000379:methods; D019231:Tooth Preparation, Prosthodontic / Q000379:methods*; D015036:Zinc Phosphate Cement
chemical_list: D015036:Zinc Phosphate Cement