title: New die design for dimensional accuracy assessment of crown castings.
abstract: OBJECTIVE
  The aim of this study was to introduce a newly designed die for ceramometal restoration, and to compare the dimensional accuracy with the traditional complete-crown design. Two methods of dimensional accuracy assessment, vertical axial discrepancy and transverse diametral percentage, were compared.
  
  
  METHODS
  Patterns were prepared from two different die designs--complete crown and ceramometal. Two investments available for titanium crown casting were used, Titavest CB and T-invest C & B. Titanium castings were made from each investment with a high-pressure casting machine. Vertical axial discrepancy of casting was determined by measuring the discrepancy for each set of wax patterns and their castings on the same die under a traveling microscope. Dimensional accuracy was expressed as vertical axial discrepancy and by transforming the vertical axial discrepancy into transverse diametral percentage.
  
  
  RESULTS
  Both dies produced undersized castings with T-invest C & B and oversized castings with Titavest CB. Dimensional accuracy assessment of the two different types of crown casting design showed no significant difference in vertical axial discrepancy.
  
  
  CONCLUSIONS
  Compared to the traditional transverse diametral percentage calculation, the vertical axial discrepancy assessment is independent of the die's dimensions. The two types of investment materials studied resulted in castings with different dimensional accuracies.
authors.affiliation: Faculty of Dentistry, University of Hong Kong, China. dannylow@scientist.com
authors.forename: Danny
authors.initials: D
authors.lastname: Low
mesh_terms: D003442:Crowns; D003734:Dental Casting Investment / Q000737:chemistry; D003735:Dental Casting Technique / Q000295:instrumentation*; D017267:Dental Prosthesis Design / Q000295:instrumentation*; D006801:Humans; D016876:Metal Ceramic Alloys / Q000737:chemistry; D008853:Microscopy; D018709:Statistics, Nonparametric; D013499:Surface Properties; D014025:Titanium / Q000737:chemistry
chemical_list: D003734:Dental Casting Investment; D016876:Metal Ceramic Alloys; D014025:Titanium