title: Effect of implant angulation on attachment retention in mandibular two-implant overdentures: a clinical study.
abstract: OBJECTIVE
  Attachment wear can affect the performance of mandibular two-implant overdentures (IODs). This prospective clinical study aimed to investigate the effect of interimplant angulation on the retention achieved by two attachment systems at different time points within 1 year of wearing IODs.
  
  
  METHODS
  Twenty-four patients (mean age = 73.2 years; standard deviation (SD) = 3.1) wearing IODs opposed by conventional maxillary complete dentures were randomly assigned to two groups in two-by-two crossover design. Retentive Anchor (RA) and Locator (LA) were installed in the IODs of both groups for 1 year, sequentially. Coronal and sagittal interimplant angulation were measured on posterior-anterior and lateral cephalometric radiographs. Retention was measured at baseline, 1 week, 3, 6, and 12 months postattachment installation. Data were analyzed using mixed models with α = 0.05.
  
  
  RESULTS
  Mean coronal and sagittal interimplant angulations were 4.6 (SD = 2.9) and 3.5 (SD = 2.6) degrees, respectively. Only with LAs a statistically significant decrease was found in retention (average 1.1 Newton; standard error = 0.38; p = .007) per 1 degree increased sagittal interimplant angulation.
  
  
  CONCLUSIONS
  Increased interimplant angulation appears to have higher impact on the retention of LA than of RA attachments. The effect of larger interimplant angulation on the loss of attachment retention and its clinical implications should be further assessed.
authors.affiliation: Division of Restorative Dentistry, Faculty of Dentistry, McGill University, Montreal, QC, Canada.
authors.forename: Zaher
authors.initials: Z
authors.lastname: Jabbour
authors.forename: Olivier
authors.initials: O
authors.lastname: Fromentin
authors.forename: Claire
authors.initials: C
authors.lastname: Lassauzay
authors.forename: Samer
authors.initials: S
authors.lastname: Abi Nader
authors.forename: José A
authors.initials: JA
authors.lastname: Correa
authors.forename: Jocelyne
authors.initials: J
authors.lastname: Feine
authors.forename: Rubens F
authors.initials: RF
authors.lastname: de Albuquerque Junior
mesh_terms: D000368:Aged; D002508:Cephalometry; D018592:Cross-Over Studies; D003758:Dental Implantation, Endosseous / Q000379:methods*; D019094:Dental Prosthesis, Implant-Supported; D003779:Denture Design; D003834:Denture Precision Attachment; D003781:Denture Retention / Q000379:methods*; D003828:Denture, Overlay; D005260:Female; D006801:Humans; D008297:Male; D008334:Mandible / Q000000981:diagnostic imaging / Q000601:surgery; D008855:Microscopy, Electron, Scanning; D011446:Prospective Studies; D016896:Treatment Outcome; D055114:X-Ray Microtomography
keywords: implant attachment; interimplant angulation; mandibular two-implant overdenture; retention