title: Three-dimensional accuracy of different correction methods for cast implant bars.
abstract: OBJECTIVE
  The aim of the present study was to evaluate the accuracy of three techniques for correction of cast implant bars.
  
  
  METHODS
  Thirty cast implant bars were fabricated on a metal master model. All cast implant bars were sectioned at 5 mm from the left gold cylinder using a disk of 0.3 mm thickness, and then each group of ten specimens was corrected by gas-air torch soldering, laser welding, and additional casting technique. Three dimensional evaluation including horizontal, vertical, and twisting measurements was based on measurement and comparison of (1) gap distances of the right abutment replica-gold cylinder interface at buccal, distal, lingual side, (2) changes of bar length, and (3) axis angle changes of the right gold cylinders at the step of the post-correction measurements on the three groups with a contact and non-contact coordinate measuring machine. One-way analysis of variance (ANOVA) and paired t-test were performed at the significance level of 5%.
  
  
  RESULTS
  Gap distances of the cast implant bars after correction procedure showed no statistically significant difference among groups. Changes in bar length between pre-casting and post-correction measurement were statistically significance among groups. Axis angle changes of the right gold cylinders were not statistically significance among groups.
  
  
  CONCLUSIONS
  There was no statistical significance among three techniques in horizontal, vertical and axial errors. But, gas-air torch soldering technique showed the most consistent and accurate trend in the correction of implant bar error. However, Laser welding technique, showed a large mean and standard deviation in vertical and twisting measurement and might be technique-sensitive method.
authors.affiliation: Department of Prosthodontics and Dental Research Institute, School of Dentistry, Seoul National University, Seoul, Republic of Korea.
authors.forename: Ji-Yung
authors.initials: JY
authors.lastname: Kwon
authors.affiliation: Department of Prosthodontics and Dental Research Institute, School of Dentistry, Seoul National University, Seoul, Republic of Korea.
authors.forename: Chang-Whe
authors.initials: CW
authors.lastname: Kim
authors.affiliation: Department of Prosthodontics and Dental Research Institute, School of Dentistry, Seoul National University, Seoul, Republic of Korea.
authors.forename: Young-Jun
authors.initials: YJ
authors.lastname: Lim
authors.affiliation: Department of Prosthodontics and Dental Research Institute, School of Dentistry, Seoul National University, Seoul, Republic of Korea.
authors.forename: Ho-Beom
authors.initials: HB
authors.lastname: Kwon
authors.affiliation: Department of Prosthodontics and Dental Research Institute, School of Dentistry, Seoul National University, Seoul, Republic of Korea.
authors.forename: Myung-Joo
authors.initials: MJ
authors.lastname: Kim
keywords: Accuracy; Additional casting; Axis angle; Cast implant bar; Gas-air torch soldering; Laser welding