title: Static implant loading caused by as-cast metal and ceramic-veneered superstructures.
abstract: BACKGROUND
  The passive fit of superstructures for implant-supported restorations is affected by each step of the fabrication process. In this context the question arises whether ceramic veneering would increase static implant loading.
  
  
  OBJECTIVE
  The purpose of this study was to quantify the strain development of various fixed partial dentures (FPDs) both in the as-cast condition and after ceramic veneering.
  
  
  METHODS
  Four different types (n = 10) of 5-unit FPDs (cementable, screw retained/plastic cylinder, screw retained/gold cylinder, screw retained/cemented) representing commonly used types of FPDs were investigated before and after ceramic veneering. Three implants were placed in a model simulating a patient situation, and strain gauges were mounted mesially and distally adjacent to the implants. The strain development was recorded during cement setting (provisional cement) and screw fixation. The data were analyzed statistically using multivariate 2-sample tests (alpha=.1).
  
  
  RESULTS
  All FPDs revealed measurable amounts of strain. Neither the type of retention nor the mode of fabrication for conventional screw-retained FPDs had a significant influence on strain development. Ceramic veneering caused an increase in strain development for the conventional fixed partial dentures tested. The lowest strains were found in FPDs cemented to gold cylinders on the model for the metal frames and the ceramic-veneered FPDs.
  
  
  CONCLUSIONS
  Conventional procedures were unable to produce superstructures with absolute passive fit. Ceramic veneering appeared to increase strain development and, thus, inaccuracy of the fit. The technique of cementing superstructures to prefabricated components directly on the implants may compensate for dimensional errors caused by impression making and superstructure fabrication.
authors.affiliation: Department of Prosthodontics, University of Erlangen-Nuremberg, Nuremberg, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Karl
authors.forename: Silke
authors.initials: S
authors.lastname: Rosch
authors.forename: Friedrich
authors.initials: F
authors.lastname: Graef
authors.forename: Thomas D
authors.initials: TD
authors.lastname: Taylor
authors.forename: Siegfried M
authors.initials: SM
authors.lastname: Heckmann
mesh_terms: D002484:Cementation; D003735:Dental Casting Technique; D015921:Dental Implants; D003761:Dental Impression Technique; D003776:Dental Porcelain / Q000737:chemistry*; D019094:Dental Prosthesis, Implant-Supported; D003801:Dental Veneers; D003779:Denture Design; D003781:Denture Retention / Q000145:classification; D003830:Denture, Partial, Fixed; D006047:Gold Alloys / Q000737:chemistry; D006801:Humans; D008422:Materials Testing; D016876:Metal Ceramic Alloys / Q000737:chemistry*; D010969:Plastics / Q000737:chemistry; D013314:Stress, Mechanical
chemical_list: D015921:Dental Implants; D006047:Gold Alloys; D016876:Metal Ceramic Alloys; D010969:Plastics; D003776:Dental Porcelain