title: Trend of change in retentive force for bar attachments with different materials.
abstract: BACKGROUND
  Attachment wear can decrease the retentive force of 2-implant overdentures (2-IODs).
  
  
  OBJECTIVE
  The purpose of this in vitro study was to investigate the trend of change in retentive force for 6 different bar attachments during dislodgement.
  
  
  METHODS
  Round and Dolder bars were made of platinum-added gold alloy (PGA), cobalt chromium alloy (Co-Cr), and commercially pure titanium grade IV (Ti). Clips were made of PGA. Retentive force was measured during 7200 dislodging cycles. Simple linear regression analysis was performed in order to investigate the relationship between number of cycles and retentive force (P<.05). Subsequently, wear debris was analyzed, and the surface of the attachments was observed.
  
  
  RESULTS
  The retentive force of the Co-Cr round bar attachment (CoCr-R) increased from 57.5 N to 68.3 N and the Ti round bar attachment (Ti-R) from 54.8 N to 59.7 N. However, the retentive force of the PGA round bar attachment (PGA-R) decreased from 69.3 N to 64.0 N. A positive relationship was found between the number of cycles and the retentive force of both CoCr-R and Ti-R. The composition of the wear debris was almost the same as for PGA. For the Dolder bar attachment, no changes were seen in retentive force (between 7.0 N to 12.0 N).
  
  
  CONCLUSIONS
  For the round bar attachment, the PGA clip and PGA bar showed wear. The retentive force of PGA-R slightly decreased. The retentive force of CoCr-R and Ti-R tended to increase. For the Dolder bar attachment, all 3 types of bar attachment showed no wear.
authors.affiliation: Graduate student, Complete Denture Prosthodontics, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan.
authors.forename: Marie
authors.initials: M
authors.lastname: Saito
authors.affiliation: Assistant Professor, Complete Denture Prosthodontics, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan. Electronic address: m.kanazawa.gerd@tmd.ac.jp.
authors.forename: Manabu
authors.initials: M
authors.lastname: Kanazawa
authors.affiliation: Professor, Oral Biomaterials Engineering, School of Oral Health Care Sciences Course for Oral Health Engineering, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan.
authors.forename: Hidekazu
authors.initials: H
authors.lastname: Takahashi
authors.affiliation: Professor, Advanced Biomaterials, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan.
authors.forename: Motohiro
authors.initials: M
authors.lastname: Uo
authors.affiliation: Professor, Complete Denture Prosthodontics, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan.
authors.forename: Shunsuke
authors.initials: S
authors.lastname: Minakuchi
mesh_terms: D002857:Chromium / Q000032:analysis; D002858:Chromium Alloys / Q000737:chemistry; D003035:Cobalt / Q000032:analysis; D017076:Computer-Aided Design; D003300:Copper / Q000032:analysis; D003764:Dental Materials / Q000737:chemistry*; D019094:Dental Prosthesis, Implant-Supported; D019554:Dental Restoration Wear; D003779:Denture Design; D003781:Denture Retention / Q000295:instrumentation*; D003828:Denture, Overlay; D006046:Gold / Q000032:analysis; D006047:Gold Alloys / Q000737:chemistry; D006801:Humans; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D010165:Palladium / Q000032:analysis; D010984:Platinum / Q000032:analysis / Q000737:chemistry; D012834:Silver / Q000032:analysis; D013052:Spectrometry, X-Ray Emission; D013314:Stress, Mechanical; D013499:Surface Properties; D014025:Titanium / Q000032:analysis / Q000737:chemistry; D015032:Zinc / Q000032:analysis
chemical_list: D002858:Chromium Alloys; D003764:Dental Materials; D006047:Gold Alloys; D002857:Chromium; D003035:Cobalt; D012834:Silver; D010984:Platinum; D010165:Palladium; D006046:Gold; D003300:Copper; D014025:Titanium; D015032:Zinc