title: Strength of CAD/CAM-generated esthetic ceramic molar implant crowns.
abstract: OBJECTIVE
  One-visit in-office CAD/CAM fabrication of esthetic ceramic crowns as a superstructure for posterior implants is quite new. The aim of the study was to evaluate the strength of esthetic ceramic CAD/CAM crowns with varied occlusal thickness and seated with adhesive and nonadhesive cements on titanium and zirconia abutments.
  
  
  METHODS
  Esthetic ceramic CAD/CAM-generated molar crowns (n = 15 per group) with occlusal thicknesses of 0.5 mm and 1.5 mm were seated on titanium (1) and zirconia (2) abutments: noncemented (a) and with nonadhesive cement (b) or 2 adhesive resin-based cements (c) and (d). In addition, 15 molar crowns with 5.5-mm occlusal thickness were seated on short zirconia abutments (3) using cements (c) and (d). All crowns had the identical occlusal morphology and were loaded with a crosshead speed of 0.5 mm/min until fracture. Load data were analyzed using 2-way ANOVA, the Scheffé test, and Weibull probability of failure analysis.
  
  
  RESULTS
  Fracture loads of 1.5-mm occlusal thickness crowns (a, b, c, d) were higher (P < .001) than those of 0.5-mm crowns (except for group ld). Occlusal 5.5-mm crowns on short zirconia abutments had similar (2c) or less (2d) strength than the respective 1.5-mm crowns. Nonadhesive crowns (1b, 2b) were weaker (P < .001) than adhesive crowns (1c, 1d, 2c, 2d). Fracture loads of 0.5- and 1.5-mm crowns were significantly higher on titanium than on zirconia abutments with both cements. Adhesive cement d generally showed higher fracture loads than c on both titanium and zirconia.
  
  
  CONCLUSIONS
  Esthetic ceramic CAD/CAM molar implant crowns gained high strength with adhesive cements on both titanium and zirconia implant abutments compared to nonadhesive cementation.
authors.affiliation: Division of Computer Restorations, Department of Preventive Dentistry, Periodontology and Cariology, Center for Dental and Oral Medicine, University of Zurich, Zurich, Switzerland.
authors.forename: Daniel
authors.initials: D
authors.lastname: Wolf
authors.forename: Andreas
authors.initials: A
authors.lastname: Bindl
authors.forename: Patrick R
authors.initials: PR
authors.lastname: Schmidlin
authors.forename: Heinz
authors.initials: H
authors.lastname: Lüthy
authors.forename: Werner H
authors.initials: WH
authors.lastname: Mörmann
mesh_terms: D000704:Analysis of Variance; D002484:Cementation / Q000379:methods; D017076:Computer-Aided Design; D003442:Crowns; D000044:Dental Abutments; D003722:Dental Alloys; D003776:Dental Porcelain; D017267:Dental Prosthesis Design; D019094:Dental Prosthesis, Implant-Supported; D003799:Dental Stress Analysis; D004955:Esthetics, Dental; D008963:Molar; D018709:Statistics, Nonparametric; D016019:Survival Analysis; D014025:Titanium; D015040:Zirconium
chemical_list: D003722:Dental Alloys; D003776:Dental Porcelain; D015040:Zirconium; D014025:Titanium; C028541:zirconium oxide