title: Novel method for titanium crown casting using a combination of wax patterns fabricated by a CAD/CAM system and a non-expanded investment.
abstract: OBJECTIVE
  For titanium casting, most commercial investments for titanium recommend casting at a low mold temperature to reduce oxidation. However, the thermal expansion values of the molds at low casting temperatures may be insufficient. The purpose of the current study was to investigate the possibility of obtaining accurate titanium crown casts using wax pattern fabricated by a CAD/CAM system with a non-expanded mold.
  
  
  METHODS
  Three types of experimental magnesia-based investments (A, B and C) were made and their properties were evaluated for dental use. Two kinds of wax patterns for full-coverage coping crowns (S-0: cement space of 0 microm; S-20: cement space of 20 microm) were fabricated using a commercial CAD/CAM system. A traditional method (TM) using inlay wax was performed for comparison. The investment for titanium casting was decided from the fundamental data of experimental investments. Titanium crowns were replaced on the stone die and the thickness of the cement layer was evaluated.
  
  
  RESULTS
  There were no significant differences for the setting time and setting expansion among the experimental investments, but the aluminous cement content played a role in hardening and contracting the mold. The fit of the titanium crowns differed significantly between the TM and the CAD/CAM system. The ranges of thickness obtained from the TM, S-0 and S-20 were 20.78-357.88 microm, 25.12-107.46 microm and 17.84-58.92 microm, respectively.
  
  
  CONCLUSIONS
  High quality titanium crown casting was obtained using a combination of wax patterns fabricated by a CAD/CAM system and a non-expanded MgO-based investment.
authors.affiliation: Department of Oral Biomaterials & Technology, Showa University School of Dentistry, 1-5-8 Hatanodai, Tokyo, Japan.
authors.forename: Zutai
authors.initials: Z
authors.lastname: Zhang
authors.forename: Yukimichi
authors.initials: Y
authors.lastname: Tamaki
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Hotta
authors.forename: Takashi
authors.initials: T
authors.lastname: Miyazaki
mesh_terms: D000704:Analysis of Variance; D017076:Computer-Aided Design; D003442:Crowns; D003734:Dental Casting Investment; D003735:Dental Casting Technique; D017267:Dental Prosthesis Design / Q000379:methods*; D005240:Feasibility Studies; D007283:Inlay Casting Wax; D008277:Magnesium Oxide; D003765:Models, Dental; D018709:Statistics, Nonparametric; D014025:Titanium
chemical_list: D003734:Dental Casting Investment; D008277:Magnesium Oxide; D007283:Inlay Casting Wax; D014025:Titanium