Interfacial reactions of cast titanium with mold materials.
OBJECTIVE
Dental casting requires replication of complex shapes with high fidelity. To achieve this objective, the problem of scale formation on titanium dental castings must be overcome. Scaling occurs readily at high temperatures because of the high reactivity of molten titanium with investment materials. The purpose of this study was to examine the effectiveness of using stable oxide coatings on the mold surface to reduce the interfacial reactions.


METHODS
A traditional phosphate-bonded dental investment, a commercial titanium investment, and an experimental oxide coating were used for the molds. Pure titanium samples were cast, divested, and prepared for scanning electron microscopic and energy dispersive x-ray spectroscopic analyses.


RESULTS
Layers of 7- to 10-micron-thick scale were formed on titanium castings during reaction with traditional mold materials. Interface reaction was reduced between the molten titanium and the investment material when yttrium oxide or zirconium oxide coatings were applied to the mold before casting.


CONCLUSIONS
Less titanium-mold interfacial reactions occurred when protective coatings were used as diffusion barriers for titanium casting. Y2O3-coating oxide particles applied without binder were entrapped in the cast titanium surface layer. Further study of a binder system for Y2O3 coating is needed.
Wang
R R
RR
Department of Restorative Dentistry, Case Western Reserve University School of Dentistry, Cleveland, Ohio 44106, USA. rxw26@po.cwru.edu
Welsch
G E
GE
Castro-Cedeno
M
M
D003734:Dental Casting Investment / Q000032:analysis / Q000737:chemistry*; D003735:Dental Casting Technique; D004347:Drug Interactions; D004577:Electron Probe Microanalysis; D008855:Microscopy, Electron, Scanning; D013499:Surface Properties; D014025:Titanium / Q000032:analysis / Q000737:chemistry*; D015019:Yttrium / Q000032:analysis / Q000737:chemistry; D015040:Zirconium / Q000032:analysis / Q000737:chemistry
D003734:Dental Casting Investment; D015019:Yttrium; D015040:Zirconium; D014025:Titanium; C028541:zirconium oxide; C091417:yttria