抄録
The usage of a newly-developed quick-heating gypsum-bonded investment material is becoming more popular in daily laboratory work because of the shorter time required from investing to casting.
Since setting expansion of this investment material stops when heating begins, the timing of when to commence heating is very important for the accuracy of cast crowns.
The purpose of this study was toclarify the freedom of changing the timing regarding the fitting accuracy of cast crowns.
The conclusions were as follows:
1. When heating commenced within 2.5 hours of investing, the accuracy of the crowns fabricated with this quick-heating investment material (SHOFU Cristobalite PF) was as good as those fabricated with conventional gypsum-bonded investment.
2. If heating commenced more than 2.5 hours after investing, the cast crowns showed a slightly larger vertical seating discrepancy, however, this was still within the range of clinical acceptability.
3. In spite of the fact that setting expansion of this quick-heating investment material stopped 2 hours after investing, casting inaccuracy continued to change. Thus it was suggested that anisotropic mold expansion resulting from setting and thermal expansion of the investment affected casting accuracy.
