高温埋没材を用いた鋳造冠内面の形状変化

抄録

In order to investigate the effects of the expansion anisotropy of high-temperature investing materials on the morphology of the inside of cast crowns, cast crowns of nickel-chromealloy (Hi-chrome soft*) were prepared using two types of high-temperature investing materials (plaster and phostphate) and three methods of ring buffering (lined ring, unlined ring, ringless). Morphological changes inside the crowns were then determined with a three-dimensional measuring system. The effects of the colloidal silic solution used for the phosphate investing material on the precision of dimensions inside the crown were also determined. The following results were obtained.
1. When plaster or phosphate was used with or without a lined ring, the overall dimensions of the inside of the crown were larger than those of the prototype. With plaster the internal form was linear, but with phosphate it tended to taper off toward the cervical area.
2. When plaster or phosphate was used with an unlined ring, the internal dimensions of the crown were decreased in the cervical area and increased in height, compared with the prototype. The crown showed a tapering internal form with both plaster and phosphate.
3. The internal dimensions of the cervical area of the crown was increased by 43μm when the ring was buffered (lined with ceramic fiber sheet).
4. When the concentration of the colloidal silica solution was increased from 10% to 30%, the expansion of the internal cervical radius of the cast crown increased from-51μm to 33μm. However, this value decreased to 20μm when the concentration was 40%.