title: Fit of metal ceramic crowns cast in Au-1.6 wt% Ti alloy for different abutment finish line curvature.
abstract: OBJECTIVE
  The purpose of this study was to evaluate the fit of metal ceramic crowns cast in Au-1.6 wt% Ti alloy and investigate the effect of abutment finish line curvature on the fit of crowns.
  
  
  METHODS
  Three types of finish line curvature abutments were prepared (1, 3 and 5mm-curvature). For each type of abutment, five metal ceramic crowns of the facial veneered type were fabricated, which were cast in Au-1.6 wt% Ti alloy. Used as controls, another fifteen specimens were made from a commercially available gold alloy. The fit was measured in the as-cast and after porcelain application.
  
  
  RESULTS
  In the as-cast specimens, the greater the finish line curvature was, the larger the gaps exhibited at the mesial and distal margins of copings, compared with labial and lingual margins. The distal margin of copings for 5mm-curvature abutments showed the largest gap (35 (7) microm). After porcelain application, the greater was the finish line curvature, the larger the labial marginal gap became (mean 44, 34, 25 microm, respectively, for 5, 3, 1mm-curvature). However, there was no significant difference on marginal gaps between specimens of Au-1.6 wt% Ti alloy and control gold alloy.
  
  
  CONCLUSIONS
  This study indicated that the metal ceramic crowns cast in Au-1.6 wt% Ti alloy had equivalent accuracy to those that cast in control gold alloy, and the abutment finish line curvature had a significant effect on the marginal fit of metal ceramic crowns.
authors.affiliation: Division of Fixed Prosthodontics, Department of Restorative Dentistry, Graduate School of Dentistry, Tohoku University, 4-1 Seiryou-machi, Aoba-ku, Sendai 980-8575, Japan. taojxtohoku@hotmail.com
authors.forename: Jianxiang
authors.initials: J
authors.lastname: Tao
authors.forename: Masanobu
authors.initials: M
authors.lastname: Yoda
authors.forename: Kohei
authors.initials: K
authors.lastname: Kimura
authors.forename: Osamu
authors.initials: O
authors.lastname: Okuno
mesh_terms: D003442:Crowns; D000044:Dental Abutments; D003735:Dental Casting Technique; D018772:Dental Marginal Adaptation; D017267:Dental Prosthesis Design; D006047:Gold Alloys; D016876:Metal Ceramic Alloys; D017755:Prosthesis Fitting; D014025:Titanium
chemical_list: D006047:Gold Alloys; D016876:Metal Ceramic Alloys; D014025:Titanium