title: Removable four implant-supported mandibular overdentures rigidly retained with telescopic crowns or milled bars: a 3-year prospective study.
abstract: OBJECTIVE
  The present study evaluated implant survival/success rate, peri-implant parameters and prosthodontic maintenance efforts for four implant-supported mandibular overdentures (IOD) rigidly retained on either milled bar or double crowns (telescopic) attachments.
  
  
  METHODS
  In a randomized prospective trial, 51 patients with edentulism received four mandibular interforaminal implants and complete maxillary dentures. For IOD, rigid denture stabilization was chosen randomly selecting 26 patients for milled bars (group I) and 25 patients for double (telescopic) crowns (group II). During a 3-year follow-up period, implant survival/success, peri-implant parameters (marginal bone resorption, pocket depth, plaque-, bleeding-, gingival index [BI and GI], calculus) and prosthodontic maintenance efforts were evaluated and compared between both retention modalities used.
  
  
  RESULTS
  Forty-five patients (23 group I, 22 group II) were available for a 3-year follow-up (dropout rate: 11.8%) presenting a high implant survival/success rate (100%). Peri-implant marginal bone resorption, pocket depth as well as BI and GI did not differ for both rigid retention modalities. However, annually higher values for plaque- (NS) and calculus index (P<0.035) were noticed for the bar (group I) than for the telescopic crown (group II) attachments. Prevalence of prosthodontic maintenance did not differ between both retention modalities (group I: 0.41/maintenance efforts/year/patients vs. group II; 0.45 maintenance/efforts/year/patients). However, prosthodontic adaption for handling mechanism showed benefits for the bar retention.
  
  
  CONCLUSIONS
  Rigid anchoring of IOD retained either by bar or telescopic attachments showed high implant success rates and minor prosthodontic maintenance efforts regardless of retention modalities used. Stable denture retention presented healthy peri-implant structure for implants in bar and telescopic anchoring systems. Drawbacks such as higher plaque/calculus for bar retention and less favorable handling properties (output) for telescopic crown attachment leave the decision on the selection at the discretion of the clinician.
authors.affiliation: Dental School, Department of Prosthodontics, Medical University of Vienna, Vienna, Austria. krennmair@aon.at
authors.forename: Gerald
authors.initials: G
authors.lastname: Krennmair
authors.forename: Daniel
authors.initials: D
authors.lastname: Sütö
authors.forename: Rudolf
authors.initials: R
authors.lastname: Seemann
authors.forename: Eva
authors.initials: E
authors.lastname: Piehslinger
mesh_terms: D000704:Analysis of Variance; D016009:Chi-Square Distribution; D003442:Crowns; D003774:Dental Plaque Index; D017267:Dental Prosthesis Design; D019094:Dental Prosthesis, Implant-Supported; D003781:Denture Retention; D003828:Denture, Overlay; D005260:Female; D006801:Humans; D007575:Jaw, Edentulous / Q000534:rehabilitation*; D008297:Male; D008334:Mandible / Q000601:surgery; D008875:Middle Aged; D016348:Osseointegration; D011446:Prospective Studies; D016896:Treatment Outcome