title: A comparative study of gold UCLA-type and CAD/CAM titanium implant abutments.
abstract: OBJECTIVE
  The aim of this study was to evaluate the interface accuracy of computer-assisted designed and manufactured (CAD/CAM) titanium abutments and implant fixture compared to gold-cast UCLA abutments.
  
  
  METHODS
  An external connection implant system (Mark III, n=10) and an internal connection implant system (Replace Select, n=10) were used, 5 of each group were connected to milled titanium abutment and the rest were connected to the gold-cast UCLA abutments. The implant fixture and abutment were tightened to torque of 35 Ncm using a digital torque gauge, and initial detorque values were measured 10 minutes after tightening. To mimic the mastication, a cyclic loading was applied at 14 Hz for one million cycles, with the stress amplitude range being within 0 N to 100 N. After the cyclic loading, detorque values were measured again. The fixture-abutment gaps were measured under a microscope and recorded with an accuracy of ±0.1 µm at 50 points.
  
  
  RESULTS
  Initial detorque values of milled abutment were significantly higher than those of cast abutment (P<.05). Detorque values after one million dynamic cyclic loadings were not significantly different (P>.05). After cyclic loading, detorque values of cast abutment increased, but those of milled abutment decreased (P<.05). There was no significant difference of gap dimension between the milled abutment group and the cast abutment group after cyclic loading.
  
  
  CONCLUSIONS
  In conclusion, CAD/CAM milled titanium abutment can be fabricated with sufficient accuracy to permit screw joint stability between abutment and fixture comparable to that of the traditional gold cast UCLA abutment.
authors.affiliation: Department of Dentistry, School of Medicine, Ewha Womans University, Seoul, Republic of Korea.
authors.forename: Ji-Man
authors.initials: JM
authors.lastname: Park
authors.affiliation: Department of Prosthodontics, School of Dentistry, Seoul National University, Seoul, Republic of Korea.
authors.forename: Jai-Bong
authors.initials: JB
authors.lastname: Lee
authors.affiliation: Department of Prosthodontics, School of Dentistry, Seoul National University, Seoul, Republic of Korea.
authors.forename: Seong-Joo
authors.initials: SJ
authors.lastname: Heo
authors.affiliation: Department of Dentistry, School of Medicine, Ewha Womans University, Seoul, Republic of Korea.
authors.forename: Eun-Jin
authors.initials: EJ
authors.lastname: Park
keywords: CAD/CAM titanium abutments; Cyclic loading; Detorque value; Fixture-abutment gap; Gold-cast UCLA abutments