title: An in-vitro investigation of the accuracy of fit of Procera and Empress crowns.
abstract: The current study aimed to investigate the accuracy of fit and the reproducibility of inner crown profile for two types of high strength ceramics, IPS Empress and Procera. Procera and Empress crowns with four different morphologies were cemented to dies using zinc phosphate dental cement. Vertical and horizontal sections were made through each of the crown/die preparations and images of the vertical sections were compared for curvature reproduction by alignment using image processing. Measurements were made on horizontal sections to determine cement layer thickness. Alignment of the crowns using image analysis identified quantifiable variations in the inner surface profile compared with the outer surface of the die. The largest differences occurred from the cusp tips to the occlusal adaptation area and differences in surface profile were less pronounced for Procera than Empress crowns. Marginal gap varied independently of ceramic or internal crown shape from 7-529 microm for Procera and 26-548 microm for Empress. IPS Empress has a superior ability to reproduce the inner surface profile of the crown morphologies investigated compared with Procera. The reduced reproduction of surface profile was associated with an increased cement thickness at the occlusal contact area that may inadvertently lead to failure of the crowns functional characteristics.
authors.affiliation: Department of Restorative Dentistry & Periodontology, Dublin Dental School and Hospital, Ireland. garry.fleming@dental.tcd.ie
authors.forename: Garry J R
authors.initials: GJ
authors.lastname: Fleming
authors.forename: Marie M
authors.initials: MM
authors.lastname: Dobinson
authors.forename: Gabriel
authors.initials: G
authors.lastname: Landini
authors.forename: Jonathan J
authors.initials: JJ
authors.lastname: Harris
mesh_terms: D003442:Crowns; D003738:Dental Cements; D003776:Dental Porcelain; D007091:Image Processing, Computer-Assisted; D018020:Lithium Compounds; D016876:Metal Ceramic Alloys; D017755:Prosthesis Fitting / Q000592:standards; D015203:Reproducibility of Results; D014025:Titanium
chemical_list: D003738:Dental Cements; C118557:Empress 2; D018020:Lithium Compounds; D016876:Metal Ceramic Alloys; C077451:Procera; D003776:Dental Porcelain; D014025:Titanium