title: Influence of cement film thickness on the retention of implant-retained crowns.
abstract: OBJECTIVE
  The main goal of this study was to establish a new, high precision procedure to evaluate the influence of cement film thickness on the retention of cemented implant-retained crowns.
  
  
  METHODS
  Ninety-six tapered titanium abutments (6° taper, 4.3 mm diameter, Camlog) were shortened to 4 mm. Computer-aided design was used to design the crowns, and selective laser sintering, using a cobalt-chromium alloy, was used to produce the crowns. This method used a focused high-energy laser beam to fuse a localized region of metal powder to build up the crowns gradually. Before cementing, preset cement film thicknesses of 15, 50, 80, or 110 μm were established. Glass ionomer, polycarboxylate, or resin cements were used for cementation. After 3 days storage in demineralized water, the retention of the crowns was measured in tension using a universal testing machine.
  
  
  RESULTS
  The cement film thicknesses could be achieved with a high level of precision. Interactions between the factors cement and cement film thickness could be found (p ≤ 0.001). For all cements, crown retention decreased significantly between a cement film thickness of 15 and 50 μm (p ≤ 0.001). At 15 μm cement film thickness, the resin cement was the most retentive cement, followed by the polycarboxylate and then the glass ionomer cement (p ≤ 0.05).
  
  
  CONCLUSIONS
  The results suggest that cement film thickness has an influence on the retentive strength of cemented implant-retained crowns.
authors.affiliation: Private practice, Munich, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Mehl
authors.forename: Sönke
authors.initials: S
authors.lastname: Harder
authors.forename: Martin
authors.initials: M
authors.lastname: Steiner
authors.forename: Oliver
authors.initials: O
authors.lastname: Vollrath
authors.forename: Matthias
authors.initials: M
authors.lastname: Kern
mesh_terms: D002484:Cementation / Q000379:methods; D002858:Chromium Alloys / Q000737:chemistry; D017076:Computer-Aided Design; D003442:Crowns; D000044:Dental Abutments; D003738:Dental Cements / Q000737:chemistry*; D015921:Dental Implants; D003764:Dental Materials / Q000737:chemistry; D017267:Dental Prosthesis Design; D017268:Dental Prosthesis Retention; D019094:Dental Prosthesis, Implant-Supported; D003799:Dental Stress Analysis / Q000295:instrumentation; D005899:Glass Ionomer Cements / Q000737:chemistry; D006801:Humans; D007834:Lasers; D008422:Materials Testing; D011076:Polycarboxylate Cement / Q000737:chemistry; D019279:Resin Cements / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties; D013997:Time Factors; D014025:Titanium / Q000737:chemistry; D014867:Water / Q000737:chemistry
chemical_list: D002858:Chromium Alloys; D003738:Dental Cements; D015921:Dental Implants; D003764:Dental Materials; D005899:Glass Ionomer Cements; D011076:Polycarboxylate Cement; D019279:Resin Cements; D014867:Water; D014025:Titanium
keywords: CAD/CAM; Cement; crown; film thickness; implant; retrievability; titanium