title: Marginal fit of cemented and screw-retained crowns incorporated on the Straumann (ITI) Dental Implant System: an in vitro study.
abstract: OBJECTIVE
  The aim of this study was to assess the marginal fit of crowns on the Straumann (ITI) Dental Implant System with special consideration of different casting dental materials.
  
  
  METHODS
  Sixty porcelain-fused-to-metal crowns were fabricated: 18 crowns on standard cone abutments with an impression cylinder, partially prefabricated analogs, no coping and screw-retained (A); 18 crowns on solid abutments without an impression device, no analogs, no coping and cemented (B); and 18 crowns on solid abutments using an impression transfer cap, an analog with a shoulder, no coping and cemented (C). In each group, six crowns were made on epoxy mastercasts (Bluestar), six on synthetic plaster (Moldasynt) and six on super hard stone (Fujirock). Six additional crowns were fabricated with the transversal screw retention system onto the Octa system with impression transfer caps, metal analogs, gold copings and screw-retained (D). Impregum was used as impression material. Crowns of B and C were cemented with KetacCem. Crowns of A and D were fixed with an occlusal screw torqued at 15 N cm. Crowns were embedded, cut and polished. Under a light microscope using a magnification of x 100, the distance between the crown margin (CM) and the shoulder (marginal gap, MG) and the distance between the CM and the end of the shoulder (crown length, CL) was measured.
  
  
  RESULTS
  MGs were 15.4+/-13.2 microm (A), 21.2+/-23.1 microm (B), 11+/-12.1 microm (C) and 10.4+/-9.3 microm (D). No statistically significantly differences using either of the casting materials were observed. CLs were -21.3+/-24.8 microm (A), 3+/-28.9 microm (B), 0.5+/-22 microm (C) and 0.1+/-15.8 microm (D). Crowns were shorter on synthetic casting materials compared with stone casts (P<0.005).
  
  
  CONCLUSIONS
  CMs fit precisely with both cemented and screw-retained versions as well as when using no, partial or full analogs.
authors.affiliation: Department of Periodontology and Fixed Prosthodontics, University of Berne, Berne, Switzerland.
authors.forename: N A
authors.initials: NA
authors.lastname: Tosches
authors.forename: U
authors.initials: U
authors.lastname: Brägger
authors.forename: N P
authors.initials: NP
authors.lastname: Lang
mesh_terms: D002484:Cementation; D003442:Crowns; D000044:Dental Abutments; D015921:Dental Implants; D003761:Dental Impression Technique; D018772:Dental Marginal Adaptation; D017268:Dental Prosthesis Retention / Q000295:instrumentation / Q000379:methods*; D019094:Dental Prosthesis, Implant-Supported; D005899:Glass Ionomer Cements; D008277:Magnesium Oxide; D016876:Metal Ceramic Alloys; D003765:Models, Dental; D011076:Polycarboxylate Cement; D017755:Prosthesis Fitting; D019415:Torque; D015034:Zinc Oxide
chemical_list: D015921:Dental Implants; D005899:Glass Ionomer Cements; D016876:Metal Ceramic Alloys; D011076:Polycarboxylate Cement; D008277:Magnesium Oxide; C040235:Ketac-cem; D015034:Zinc Oxide