[Studies on marginal castability of cast crown].
The castability of the crown margins was studied. The smoothness and quantitative measurement of the margins were compared with the original wax patterns and their casted products. Wax patterns of the plate and crown forms were fabricated with sharp, straight and even margins. Margin angles of the wax patterns were prepared at both 20 and 40 degrees for the plate type and 20 degrees for the crown type samples. Each wax pattern was casted with Type IV gold alloy and gold-silver-palladium alloy. The casted margins were evaluated by comparing them with their original wax patterns. The results were as follows: 1. Compared to the current procedure, more precise evaluation of the marginal castability is now possible with this new method. 2. The shortness of the margins was observed in all of the casted samples. Casted samples with 20-degree margins resulted in twice as much deficiency as compared to those with 40-degree margins. 3. The smoothness and evenness of the margins were inferior in all of the casted samples when compared to their original wax patterns. 4. The margin thickness was between 50 and 70 microns when the wax patterns with sharp margins were casted. 5. A certain thickness is required at the margins of the wax patterns in order to achieve precise casted margins. In this study, it was found to be 79.1 microns.
Kokubo
S
S
Department of Prosthodontics II, Faculty of Dentistry, Tokyo Medical and Dental University.
D003442:Crowns; D003722:Dental Alloys; D003735:Dental Casting Technique; D006046:Gold; D010165:Palladium; D012834:Silver
D003722:Dental Alloys; D012834:Silver; D010165:Palladium; D006046:Gold