title: Influence of CAD/CAM scanning method and tooth-preparation design on the vertical misfit of zirconia crown copings.
abstract: OBJECTIVE
  To evaluate the influence of scanning method, finish line type and occlusal convergence angle of the teeth preparations on the vertical misfit of zirconia crown copings.
  
  
  METHODS
  20 standardized stainless-steel master dies were machined simulating full-crown preparations. The total convergence angle was 15 degrees or 20 degrees (n=10 each). Two of the finish line types: a chamfer (CH) and a shoulder (SH) were prepared around the contour of each abutment. Over these dies, 20 structures were made by CAD/CAM (Cercon, Dentsply). An optical laser digitized the wax patterns of 10 single-unit copings (WS), and 10 abutments were direct-scanned to design the cores by computer (DS). Zirconia milled caps were luted onto the models under constant seating pressure. Vertical discrepancy was assessed by SEM. Misfit data were analyzed using ANOVA and Student-Newman-Keuls (SNK) test for multiple comparisons at alpha = 0.05.
  
  
  RESULTS
  Vertical gap measurements of WS copings were significantly higher than those of DS frames (P < 0.0001). SH exhibited statistically higher discrepancies than CH when combined with a 15-degree occlusal convergence angle regardless of the scanning method (P < 0.05). The taper angle of the preparation (15 degrees vs. 20 degrees) had no effect on the marginal adaptation of chamfered samples.
authors.affiliation: Department of Prosthodontics, Faculty of Dentistry, Complutense University of Madrid, U.C.M., Pza. Ramón y Cajal, no 3, 28040, Madrid, Spain. siete_rosas.rc@hotmail.com
authors.forename: Raquel
authors.initials: R
authors.lastname: Castillo Oyagüe
authors.forename: María Isabel
authors.initials: MI
authors.lastname: Sánchez-Jorge
authors.forename: Andrés
authors.initials: A
authors.lastname: Sánchez Turrión
mesh_terms: D000704:Analysis of Variance; D002484:Cementation; D017076:Computer-Aided Design; D003442:Crowns; D000044:Dental Abutments; D018772:Dental Marginal Adaptation; D003776:Dental Porcelain / Q000737:chemistry; D017267:Dental Prosthesis Design / Q000009:adverse effects / Q000379:methods*; D007091:Image Processing, Computer-Assisted / Q000379:methods; D021621:Imaging, Three-Dimensional / Q000009:adverse effects / Q000379:methods*; D008855:Microscopy, Electron, Scanning; D017755:Prosthesis Fitting; D018709:Statistics, Nonparametric; D019231:Tooth Preparation, Prosthodontic / Q000379:methods*; D015040:Zirconium
chemical_list: D003776:Dental Porcelain; D015040:Zirconium; C028541:zirconium oxide