Effect of mold temperatures on interface between primary and secondary castings of cast-on method for precision metal frameworks.
OBJECTIVE
The purpose of the present study was to obtain fundamental data for application of the cast-on method by evaluating the effect of mold temperatures on the interface between primary and secondary castings in detail.


METHODS
Silver-palladium-gold alloy (Ag-Pd-Au), type-4 gold alloy (Type4), and chromium-cobalt alloy (Cr-Co) were used in the present study. A polished flat, square metal plate, 10.0 mm x10.0 mm x 1.0 mm, was used as the primary casting. A wax pattern, 2.0 mm in diameter and 2.0 mm thick, was prepared for the secondary casting and invested together with the primary casting. The mold was heated at 600, 700 and 800 degrees C for Ag-Pd-Au and Type4, and 700, 800 and 900 degrees C for Cr-Co. After casting, the mold was embedded and sectioned. The cross-section was observed using a scanning electron microscope (SEM) and analyzed using energy dispersive X-ray spectroscopy (EDS). The gaps between the primary and secondary castings were analyzed for each alloy by analysis of variance and Tukey's honestly significant difference test. The significance level was set at 0.05. The heated primary casting without the secondary casting was examined using a thin film X-ray diffractometer (XRD).


RESULTS
Gaps were observed between the primary and secondary castings in all examined conditions. The primary casting surface was covered with oxide layers such as CuO and Cr(2)O(3), and became rough with an increase of the mold temperature.


CONCLUSIONS
The results suggested that the cast-on method was influenced by the mold temperature.
Sakai
Tetsushi
T
Removable Partial Denture Prosthodontics, Department of Masticatory Function Rehabilitation, Tokyo Medical and Dental University, Tokyo, Japan. sakai.rpro@tmd.ac.jp
Hideshima
Masayuki
M
Takahashi
Hidekazu
H
Ichinose
Shizuko
S
Igarashi
Yoshimasa
Y