title: The Potential Risk of Conical Implant-Abutment Connections: The Antirotational Ability of Cowell Implant System.
abstract: BACKGROUND
  Conical implant-abutment connections are popular because of good antibending performance. However, the cross section is round, and the antirotational ability is questionable because restorations in the oral cavity also have to bear torsional moments resulting from chewing patterns.
  
  
  OBJECTIVE
  The purpose of this study was to investigate the antirotational ability of conical implant-abutment connections with and without an index.
  
  
  METHODS
  Conical connection implant system (Cowell Medi, Busan, South Korea) was selected. Two kinds of cyclic loading, a bending moment with (C) and without (L) a torsional moment, were respectively applied to two kinds of abutments, pure cone (N-Octa) and cone with an octagonal index (Octa). The number of cycles to fatigue and the failure modes was recorded. Morphologies of the abutments were examined with scanning electron microscopy.
  
  
  RESULTS
  Only group C(N-Octa) passed the fatigue test, whereas the other three groups failed because of different failure modes. In group L(N-Octa), all abutments generated rotation within 150 cycles. In groups C(Octa) and L(Octa), all abutments fractured but in different areas.
  
  
  CONCLUSIONS
  In Cowell implant system (taper angle = 7°), there was no antirotational ability in purely conical connections. Adding an octagonal index could provide an antirotational function but could compromise the antibending strength of the abutment.
authors.affiliation: Department of Dentistry, National Yang-Ming University, Taipei, Taiwan.
authors.forename: Kuang-Ta
authors.initials: KT
authors.lastname: Yao
authors.affiliation: Department of Biomedical Engineering, Orthopaedic Device Research Center, National Yang-Ming University, Taipei, Taiwan.
authors.forename: Hung-Chan
authors.initials: HC
authors.lastname: Kao
authors.affiliation: Department of Biomedical Engineering, Orthopaedic Device Research Center, National Yang-Ming University, Taipei, Taiwan.
authors.forename: Cheng-Kung
authors.initials: CK
authors.lastname: Cheng
authors.affiliation: Department of Chemical Engineering and Biotechnology & Institute of Chemical Engineering, National Taipei University of Technology, Taipei, Taiwan.|Division of Medical Engineering Research, National Health Research Institutes, Miaoli, Taiwan.
authors.forename: Hsu-Wei
authors.initials: HW
authors.lastname: Fang
authors.affiliation: Department of Medical Research, Mackay Memorial Hospital, Taipei, Taiwan.
authors.forename: Chang-Hung
authors.initials: CH
authors.lastname: Huang
authors.affiliation: School of Dentistry, National Yang-Ming University, Taipei, Taiwan.
authors.forename: Ming-Lun
authors.initials: ML
authors.lastname: Hsu
mesh_terms: D017076:Computer-Aided Design; D059605:Dental Implant-Abutment Design; D003799:Dental Stress Analysis; D066298:In Vitro Techniques; D008409:Mastication; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D012399:Rotation; D013499:Surface Properties; D013718:Tensile Strength; D014025:Titanium; D019415:Torque
chemical_list: D014025:Titanium
keywords: antirotational ability; conical; dental implant; implant-abutment connection; index