title: Retention of maxillary implant overdenture bars of different designs.
abstract: BACKGROUND
  The specific degree of retention for overdenture attachments is unknown in relation to design, location, and alignment to supporting dental implants.
  
  
  OBJECTIVE
  The purpose of this study was to evaluate the initial retention characteristics of 5 implant maxillary overdenture designs under in vitro dislodging forces.
  
  
  METHODS
  A simulated edentulous maxilla was fabricated with 4 screw-type 3.75 x 13-mm implants anteriorly. Five overdenture designs with the following attachments were evaluated: 4 plastic Hader clips with an EDS bar; 2 plastic anterior Hader clips with an identical EDS bar; 2 Hader clips with 2 posterior ERA attachments; 3 Zaag attachments on a bar; and 4 Zaag attachments with no bar. Overdentures were fabricated with full palatal coverage. Each design was subjected to 10 consecutive retention pulls on a universal testing machine. Data were subjected to analysis of variance and t tests to determine differences.
  
  
  RESULTS
  The highest average value after 10 pulls was 19.8 lb for the combination ERA and Hader clip design. The lowest retentive values were recorded for the 2 and 4 Hader clip designs (5.08 +/- 0.89 lb and 5.06 +/- 0.67 lb, respectively). Retention decreased over the course of consecutive pulls for all designs, especially for the most retentive designs. The smallest retention decrease occurred with the least retentive designs.
  
  
  CONCLUSIONS
  The results of this in vitro study suggest that the precise selection and placement of attachments may affect the clinical success of maxillary implant-retained overdentures.
authors.affiliation: School of Dentistry, University of California at Los Angeles, 90095, USA.
authors.forename: B H
authors.initials: BH
authors.lastname: Williams
authors.forename: K T
authors.initials: KT
authors.lastname: Ochiai
authors.forename: S
authors.initials: S
authors.lastname: Hojo
authors.forename: R
authors.initials: R
authors.lastname: Nishimura
authors.forename: A A
authors.initials: AA
authors.lastname: Caputo
mesh_terms: D016734:Dental Clasps; D019094:Dental Prosthesis, Implant-Supported; D003799:Dental Stress Analysis; D003779:Denture Design; D003834:Denture Precision Attachment; D003781:Denture Retention / Q000295:instrumentation*; D003827:Denture, Complete, Upper; D003828:Denture, Overlay; D006801:Humans