title: Maxillary overdentures supported by four or six implants in the anterior region: 5-year results from a randomized controlled trial.
abstract: To compare a four- and six-implant maxillary overdenture after an observation period of 5 years.
  
  
  
  Fifty subjects with functional problems concerning their maxillary denture, who had ample bone volume in the anterior region to place four or six implants, were included and randomly assigned to either group. Implant and overdenture survival, clinical performance, marginal bone loss and patient satisfaction were assessed.
  
  
  
  Forty-six patients completed the 5-year follow-up. One implant failed in the six implants group (99.2% survival) and none in the four implants group (100% survival). No overdentures had to be replaced during the observation period and the number of complications was limited. Clinical function was good, with no difference in clinical parameters between the groups. Mean marginal bone resorption was 0.50 ± 0.37 and 0.52 ± 0.43 mm in the four and six implant group respectively.
  
  
  
  In patients with functional complaints of their maxillary denture, bar-supported overdentures on four implants in the anterior maxillary region were not inferior to overdentures supported by six implants after 5 years of function. Implant survival and patient satisfaction were high, clinical parameters favourable, bone loss and complications to the denture were minor in both groups (Clinical trial registration number: NTR2969).
authors.affiliation: Department of Fixed and Removable Prosthodontics and Biomaterials, Dental School, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands.
authors.forename: Wim
authors.initials: W
authors.lastname: Slot
authors.affiliation: Department of Oral and Maxillofacial Surgery, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands.
authors.forename: Gerry M
authors.initials: GM
authors.lastname: Raghoebar
authors.affiliation: Department of Fixed and Removable Prosthodontics and Biomaterials, Dental School, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands.
authors.forename: Marco S
authors.initials: MS
authors.lastname: Cune
authors.affiliation: Department of Oral and Maxillofacial Surgery, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands.
authors.forename: Arjan
authors.initials: A
authors.lastname: Vissink
authors.affiliation: Department of Fixed and Removable Prosthodontics and Biomaterials, Dental School, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands.|Department of Oral and Maxillofacial Surgery, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands.
authors.forename: Henny J A
authors.initials: HJ
authors.lastname: Meijer
mesh_terms: D015921:Dental Implants; D019094:Dental Prosthesis, Implant-Supported; D003781:Denture Retention; D003828:Denture, Overlay; D005500:Follow-Up Studies; D006801:Humans; D007575:Jaw, Edentulous; D008437:Maxilla; D017060:Patient Satisfaction; D016896:Treatment Outcome
chemical_list: D015921:Dental Implants
keywords: dental implants; edentulous; healthy ageing; maxilla; overdenture