MARGINAL FIT OF GLASS INFILTRATED ALUMINA CORE FABRICATED FROM ALUMINA TAPES / 대한치과보철학회지

The purpose of this study was to compare the marginal fit of all ceramic crowns prepared from alumina slip casting, which is consistent with the conventional In-ceram system, and those fabricated from alumina tapes which is currently under development in an effort to alleviate complexities involved in the forming procedure of the In-ceram crown core. All ceramic crowns, made of In-ceram(slip casting) and alumina tapes(Doctor blade casting), were prepared with 90degreeand 135degreeshoulder margins. The crowns were cemented with a glass ionomer cement and embeded in epoxy resin. The embedded crowns were sectioned faciolingually and mesiodistally and marginal discrepancies and marginal gaps were measured under the Measurescope MM II. The measurements were analyzed using Wilcoxon rank sum test and Kruskal-Wallis test and the results were as follows: 1. In the case of 90degreeshoulder margin, the combined marginal discrepancies and marginal gaps were 78.3 micrometerm and 44.4 micrometer respectively, for the all ceramic crowns fabricated using the alumina tapes. In comparison, the values were 65 micrometer and 25.5 micrometer for the In-ceram crowns. For the marginal gaps a statistical difference existed (p0.05). 2. In the case of 135degreeshoulder margin, the combined marginal discrepancy and marginal gaps were 82.1 micrometer and 40.2 micrometer respectively, for the all ceramic crowns formed with the tapes. As compared with the marginal discrepancy and gaps of the 90degreeshoulder margin in the fabricated from the alumina tapes, no significant statistical differencies were discerned in both cases (p>0.05). 3. There was no statistically significant difference in the fits among four locations around the margins of the all ceramic crowns fabricated using the alumina tapes. The results obtained in this study showed that the marginal fits of the glass infiltrated alumina cores fabricated from the alumina tapes are slightly higher value than those prepared using the In-ceram but the difference is within a clinically acceptable range.

A STUDY ON THE SURFACE ROUGHNESS OF GLAZED PORCELAIN AND POLISHED PORCELAIN / 대한치과보철학회지

Porcelain is considered to be one of the materials of choice for restoration where esthetics is of concern. But porcelain surface without final glazing treatment may induce undesirable results such as inflammatory respones on adjacent soft tissues due to plaque accumulation and increased wear of opposing teeth. Therefore, rough porcelain surface must be smoothened by final glazing treatment or chairside polishing procedure. The purpose of this study was to compare the surface roughness among self-glazed, overglazed and polished porcelain with various polishing kit, and to detect which phase of polishing is optimal in clinic. Specimens were fabricated with Vita VMK porcelain. The surface treatment of each group was performed as follows. Group 1 : overglazing treatment Group 2 : self-glazing treatment Group 3 : polishing with the Truluster Polishing System for Porcelain(Brasseler, U.S.A.) Group 4 : polishing with the Exa Cerapol Adjustment kit (Edenta dental products, Switzerland) followed by finishing with diamond-filled polishing paste Group 5 : polishing with the Shofu Porcelain Adjustment kit (Shofu inc., Japan) followed by finishing with diamond-filled polishing paste. At each polishing steps, the measurement of Ra and Rq values were performed, and the surface was examined by scanning electron microscope. The results were as follows: 1. Overglazing treatment brought smoother surface than self-glazing treatment. 2. Polishing systems without porcelain polishing paste did not make better result than self-glazing treatment. 3. Polishing system with porcelain polishing paste made similar result to overglazing treatment. 4. Applying diamond-filled polishing paste after using polishing system which has porcelain polishing paste produced surface as smooth as overglazing treatment does.