title: A systematic review of implant-supported overdentures in the edentulous maxilla, compared to the mandible: how many implants?
abstract: OBJECTIVE
  There is now overwhelming evidence from systematic reviews that a two implant overdenture is the first choice of treatment for the edentulous mandible. Conversely, consensus is lacking for implant-supported maxillary overdentures. Therefore, we systematically reviewed the treatment outcome of concepts used for implant-supported maxillary overdentures, focusing on the survival of implants, survival of maxillary overdentures and condition of the implant surrounding hard and soft tissues after a mean observation period of at least 1 year.
  
  
  METHODS
  MEDLINE (1950 to December 2013), EMBASE (1966 to December 2013) and CENTRAL (1800 to December 2013) were searched to identify eligible studies. Two reviewers independently assessed the articles using specific study design-related quality assessment forms.
  
  
  RESULTS
  Out of 195 primarily selected articles, 24 studies fulfilled the inclusion criteria. A metaanalysis showed an implant survival rate of 98.1% and overdenture survival of 99.5% per year in the case of ≥ 6 implants and a splinted (bar) anchorage. In the case of ≤ 4 implants and a splinted (bar) anchorage, implant survival rate and overdenture survival were 97.0% and 96.9% per year, respectively. In the case of ≤ 4 implants and a non-splinted anchorage (ball, locator, telescopic crown), implant survival rate and overdenture survival were 88.9% and 98.8% per year, respectively. The condition of the peri-implant tissues was not reported in most studies.
  
  
  CONCLUSIONS
  An implant-supported maxillary overdenture (all studies ≥ 4 implants) provided with a splinted anchorage is accompanied with a high implant and overdenture survival rate (both >95% per year), while there is an increased risk of implant loss when ≤ 4 implants with a non-splinted anchorage are used.
authors: Gerry M
authors: GM
authors: Raghoebar
authors: Henny J A
authors: HJ
authors: Meijer
authors: Wim
authors: W
authors: Slot
authors: James J R
authors: JJ
authors: Slater
authors: Arjan
authors: A
authors: Vissink
mesh_terms: D015921:Dental Implants; D019094:Dental Prosthesis, Implant-Supported; D003781:Denture Retention / Q000295:instrumentation; D003828:Denture, Overlay; D006801:Humans; D007575:Jaw, Edentulous / Q000534:rehabilitation* / Q000601:surgery; D008334:Mandible / Q000473:pathology* / Q000601:surgery; D008437:Maxilla / Q000473:pathology* / Q000601:surgery; D016019:Survival Analysis; D016896:Treatment Outcome
chemical_list: D015921:Dental Implants