title: Double crown-retained maxillary overdentures: 5-year follow-up.
abstract: BACKGROUND
  There is a lack of data concerning implant-supported overdentures (IODs) retained by double crowns in the edentulous maxilla.
  
  
  OBJECTIVE
  To perform a retrospective evaluation of clinical outcomes (survival/success rates) of maxillary overdentures retained on four implants via double crowns.
  
  
  METHODS
  Between 1993 and 2011, 28 patients with edentulous maxillae were restored with overdentures supported by four implants with a Morse taper connection (Ankylos, Dentsply Friadent, Mannheim, Germany) and double crowns according to the Marburg Double Crown (MDC) technique in a private practice. For retrospective evaluation of implant and prosthetic survival (in situ criterion) and success (event-free observational period), only patients attending a professional maintenance program were included (n = 20).
  
  
  RESULTS
  Twenty patients (13 female/ seven male, mean age: 63.45 ± 7.18 years) with 80 implants met the inclusion criteria. The mean follow-up period was 5.64 ± 3.50 years. One implant was lost (cumulative survival rate: 98.75%). Eight implants (10.1%) in two patients (10%) showed peri-implantitis; both patients were active smokers (cumulative success rate: 88.75%). All dentures were still functional (prosthetic survival rate 100%) at the time of investigation. Technical maintenance procedures (e.g., abutment loosening, screw loosening, acrylic fracture or relining) were required at a rate of 0.222/patient-year.
  
  
  CONCLUSIONS
  Within the limitations of this study, we conclude that MDC-IODs are a promising treatment alternative for edentulous maxillae offering high implant and prosthesis survival rates > 98% and a limited incidence of biological and technical complications after a mean observational period of >5 years.
authors.affiliation: Department of Preventive Dentistry, Periodontology and Cariology, University Medical Center Goettingen, Goettingen, Germany.
authors.forename: Eberhard
authors.initials: E
authors.lastname: Frisch
authors.forename: Dirk
authors.initials: D
authors.lastname: Ziebolz
authors.forename: Petra
authors.initials: P
authors.lastname: Ratka-Krüger
authors.forename: Sven
authors.initials: S
authors.lastname: Rinke
mesh_terms: D003442:Crowns; D017267:Dental Prosthesis Design; D019094:Dental Prosthesis, Implant-Supported; D019232:Dental Restoration Failure; D003781:Denture Retention; D003828:Denture, Overlay; D005260:Female; D006801:Humans; D007575:Jaw, Edentulous / Q000534:rehabilitation; D008297:Male; D008437:Maxilla; D008875:Middle Aged; D012189:Retrospective Studies; D016896:Treatment Outcome
keywords: dental implant; double crown; maxilla; overdenture; peri-implantitis; technical complication