title: Investigation of the wear of prefabricated attachments--an in vitro study of retention forces and fitting tolerances.
abstract: OBJECTIVE
  To quantify wear processes by measuring the retention force changes and the fitting tolerance at different prefabricated attachment systems to estimate the wear constancy and applicability in clinical practice.
  
  
  METHODS
  Seven prefabricated attachment systems (Dalbo-Classic, Dalbo-PLUS, Dalbo-Z, Mini-Gerber-PLUS, Stufenexzenter, SpharoLock, and Degussa-Kugelankersystem) with different construction and alloy composition were tested. Twenty samples of each system were subjected to 10,000 insertion-separation cycles in a wear simulator with a periodontium-simulating specimen holder. The simulator was designed to record the force needed to insert and to separate the attachment and the distance moved during the insertion and separation cycles.
  
  
  RESULTS
  All types of anchors showed wear that led to a loss or to an increase in retention force at the beginning of the wear simulation. Anchors with a plastic retention insert showed the slightest changes in retention force. The wear does not have an effect on the fitting tolerance.
  
  
  CONCLUSIONS
  Anchor systems that possess an adjustable matrix should be preferred. They allow decreasing or increasing the retention force of an anchor if this force is changed by wear. There is no risk of a loss of support if forces in occlusal direction are exerted because there is no clinically relevant change in the fitting tolerance.
authors.affiliation: Department of Preclinical Education and Experiemtntal Research, University of Bonn, Germany. stefan_bayer@gmx.net
authors.forename: Stefan
authors.initials: S
authors.lastname: Bayer
authors.forename: Manfred
authors.initials: M
authors.lastname: Grüner
authors.forename: Ludger
authors.initials: L
authors.lastname: Keilig
authors.forename: Robert
authors.initials: R
authors.lastname: Hültenschmidt
authors.forename: Claudia
authors.initials: C
authors.lastname: Nicolay
authors.forename: Christoph
authors.initials: C
authors.lastname: Bourauel
authors.forename: Karl-Heinz
authors.initials: KH
authors.lastname: Utz
authors.forename: Helmut
authors.initials: H
authors.lastname: Stark
mesh_terms: D019554:Dental Restoration Wear; D003799:Dental Stress Analysis; D003834:Denture Precision Attachment; D003781:Denture Retention / Q000379:methods*