title: Abrasion of abutment screw coated with TiN.
abstract: BACKGROUND
  Screw loosening has been a common complication and still reported frequently.
  
  
  OBJECTIVE
  The purpose of this study was to evaluate abrasion of the implant fixture and TiN coated abutment screw after repeated delivery and removal with universal measuring microscope.
  
  
  METHODS
  Implant systems used for this study were Osstem and 3i. Seven pairs of implant fixtures, abutments and abutment screws for each system were selected and all the fixtures were perpendicularly mounted in liquid unsaturated polyesther with dental surveyor. After 20 times of repeated closing and opening test, the evaluation for the change of inner surface of implant and TiN-coated abutment screw, and weight loss were measured. Mann-Whitney test with SPSS statistical software for Window was applied to analyze the measurement of weight loss.
  
  
  RESULTS
  TiN-coated abutment screws of Osstem and 3i showed lesser loss of weight than non-coated those of Osstem and 3i (P < .05, Mann-Whitney test).
  
  
  CONCLUSIONS
  Conclusively, TiN coating of abutment screw showed better resistance to abrasion than titanium abutment screw. It was concluded that TiN coating of abutment screw would reduce the loss of preload with good abrasion resistance and low coefficient of friction, and help to maintain screw joint stability.
authors.affiliation: Graduate student, Department of Prosthodontics, School of Dentistry, Chosun University, Gwangju, Korea.
authors.forename: Seok-Won
authors.initials: SW
authors.lastname: Jung
authors.forename: Mee-Kyoung
authors.initials: MK
authors.lastname: Son
authors.forename: Chae-Heon
authors.initials: CH
authors.lastname: Chung
authors.forename: Hee-Jung
authors.initials: HJ
authors.lastname: Kim