title: Screw- versus cement-retained implant prostheses: a systematic review of prosthodontic maintenance and complications.
abstract: OBJECTIVE
  This systematic review aimed to identify different prosthodontic outcomes between screw- and cement-retained implant prostheses.
  
  
  METHODS
  The relevant articles were retrieved from the following electronic databases: MEDLINE, EMBASE, PubMed (using medical subject headings), and the Cochrane Central Register of Controlled Trials (CENTRAL). The search was performed up to December 31, 2013, and was restricted to studies on human subjects reported in English. A further search was conducted through the reference lists of the articles found as well as from early online articles. Reviewed studies were those on fixed implant prostheses using different retention mechanisms such as screws or cement. Information on types of screws and mechanisms of preloading, as well as different luting cements, was collected in correlation with prosthodontic maintenance/complication issues seen in the clinical studies.
  
  
  RESULTS
  Sixty-two papers met the review criteria. There were only six randomized controlled trials and none of them included an equivalent number of screw- and cement-retained single implant crowns for comparison. Studies used different types of screws and only a few reported the preloading procedure for the prosthetic screws. Other studies involving cement-retained implant prostheses used a range of dental cements; however, some did not specify the type used. Studies reported various prosthodontic maintenance/complication issues such as screw loosening, porcelain fracture, loss of retention, and esthetic concerns. Five studies did not report any prosthodontic maintenance issues during their observation periods. More recent studies also did not report any incidence of screw loosening. Only two studies stated the standardized criteria for reporting their prosthodontic maintenance/ complication issues.
  
  
  CONCLUSIONS
  With inadequate information and various study designs, it was difficult to compare the prosthodontic outcomes between screw and cement-retained fixed implant prostheses. Both retention mechanisms showed prosthodontic maintenance/complication issues that must be considered and this review showed that the introduction of newer implant components may assist in minimizing these issues. It is also recommended that standardized criteria be used when reporting prosthodontic maintenance/complication issues to allow better comparison of data.
authors.forename: Sunyoung
authors.initials: S
authors.lastname: Ma
authors.forename: Aaron
authors.initials: A
authors.lastname: Fenton
mesh_terms: D002484:Cementation / Q000379:methods*; D003442:Crowns; D003738:Dental Cements / Q000737:chemistry; D019250:Dental Implants, Single-Tooth; D017268:Dental Prosthesis Retention / Q000295:instrumentation; D019094:Dental Prosthesis, Implant-Supported; D019232:Dental Restoration Failure; D006801:Humans
chemical_list: D003738:Dental Cements