Abstract
It was attempted to coat the refractory models by zirconia to improve a reactive layer of the pure titanium denture base cast using phosphate-bonded investment and to compare with a usual investing method.
When the coating refractory models were used, the small residual investment on the casting plate removing from the mold was observed.
The surface hardness of the castings prepared with TAIVEST was hardly different between the two samples. However, the surface hardness of the castings prepared with T-INVEST C & B was slightly greater control samples on the casting surface to a depth of about 30μm, but there was little difference between the samples for the depth.
In the coating samples, the microstructure of the surface of the castings showed almost no evident chill layer. The control samples had a chill layer and a columnar crystal layer extending from the surface toward the interior.
Use of the electron probe microanalyzer (EPMA) to determine distribution of various elements in the superficial layer of casting plates showed the reactive layer contained Si and P in control samples. In coating samples, it showed a small reactive layer contained impure elements though there was a high density of Zr of the surface layer of the castings.
The results are suggested that it is possible to improve a reactive layer of the surface of pure titanium denture base cast using phosphate-bonded investment by coating of the surface of the refractory models.
