title: The change in retentive values of locator attachments and hader clips over time.
abstract: OBJECTIVE
  The aim of this study was to examine early changes in retentive values of implant overdenture attachments during multiple pulls.
  
  
  METHODS
  Two implant attachment systems (Hader bar and clip, Locator system) were used in this study. The experimental groups were divided into yellow Hader clips, white Locator attachments, and green Locator attachments. Each group consisted of 21 matrix attachments. The attachments were placed into a custom-made acrylic resin block seated passively on another acrylic block containing a Hader bar or two Locator abutments with different angulations. Each attachment was subjected to 20 consecutive pulls using a universal testing machine. The peak load-to-dislodgement of the attachments after each pull was documented, and the percent reduction of the peak load-to-dislodgement was calculated. One-way ANOVA and Tukey's honestly significant difference test were used for data analyses. A p < or = 0.05 was considered significant.
  
  
  RESULTS
  There was a significant difference in the percent reduction in peak load-to-dislodgement between the attachments after the first pull (p= 0.005) and after the final pull (p= 0.0001). The yellow Hader clips exhibited the least percent reduction in peak load-to-dislodgement (6.50 +/- 3.59%) after the first pull, followed by the white Locator attachments (8.60 +/- 4.42%); the green Locator attachments exhibited the greatest reduction (11.05 +/- 4.94%).
  
  
  CONCLUSIONS
  The results of this in vitro study demonstrate that retentive values of the Locator attachments are reduced significantly after multiple pulls. Although this reduction might not be noticeable to the patient, it is recommended that the clinician place and remove the overdenture multiple times before delivery.
authors.affiliation: Baltimore College of Dental Surgery, Baltimore, MD 21201, USA.
authors.forename: Elizabeta
authors.initials: E
authors.lastname: Evtimovska
authors.forename: Radi
authors.initials: R
authors.lastname: Masri
authors.forename: Carl F
authors.initials: CF
authors.lastname: Driscoll
authors.forename: Elaine
authors.initials: E
authors.lastname: Romberg
mesh_terms: D000704:Analysis of Variance; D000044:Dental Abutments; D015921:Dental Implants; D017267:Dental Prosthesis Design; D017268:Dental Prosthesis Retention / Q000295:instrumentation*; D019094:Dental Prosthesis, Implant-Supported / Q000295:instrumentation*; D019232:Dental Restoration Failure; D003799:Dental Stress Analysis; D003826:Denture, Complete, Lower; D003828:Denture, Overlay; D006801:Humans; D008334:Mandible; D018709:Statistics, Nonparametric; D013314:Stress, Mechanical
chemical_list: D015921:Dental Implants