Abstract
Titanium has become popular not only as a dental implant material but also as a denture or Cr-Br material. Previously, we reported that 1.8% or more expansion of casting molds was required to create a suitable fit when used casting titanium for the superstructure of implants. The purpose of this study was to evaluate the fit of titanium castings obtained from some commercial investments for titanium. Four kinds of commercial investment for titanium (T-invest C＆B(TCB), Titavest CB (CB), Selevest SCB (SCB), Selevest D (SD) were selected and used according to the manufacturer's instructions. A tapered metal die for the fitting test based on the ADA standard was prepared. Using this die, dimensional changes by both MOD crowns cast by a special outer frame and ring shape casting were measured. Although CB showed no setting expansion, the titanium castings became oversized because of large thermal expansion. The MOD crown from SCB indicated the smallest gap in the investments tested. However, the ring casting from SCB was slightly contracted. This revealed that the expansion mechanism of SCB was unstable during heating. Both MOD and ring-shape castings from TCB were undersized. On the other hand, large marginal gaps were observed on the castings from SD, which were due to little mold expansion. These results indicated that the investments we tested in this study showed insufficient expansion to achieve an appropriate fit of the castings.
