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  • Title: Influence of finish line design on marginal adaptation of electroformed metal-ceramic crowns.
    Author: Shiratsuchi H, Komine F, Kakehashi Y, Matsumura H.
    Journal: J Prosthet Dent; 2006 Mar; 95(3):237-42. PubMed ID: 16543022.
    Abstract:
    STATEMENT OF PROBLEM: Gold electroformed metal-ceramic restorations have been promoted as alternatives to conventional metal-ceramic restorations. However, little is known about the relationship between tooth preparation design and marginal adaptation for this type of crown. PURPOSE: This study evaluated the influence of 3 different finish line designs on the marginal adaptation of electroformed metal copings and metal-ceramic crowns. MATERIAL AND METHODS: Three steel dies were prepared for maxillary central incisor crowns with 3 finish line designs: shoulder, rounded shoulder, and deep chamfer preparations. Eight standardized electroformed metal-ceramic crowns were fabricated for each group. Marginal discrepancies were measured at 60 points for each specimen along the circumferential margin at 4 sites (labial, mesial, lingual, and distal surfaces, with 15 points for each site) before and after firing procedures using a laser microscope. Data among the 3 different groups were statistically analyzed using the Kruskal-Wallis test and the Mann-Whitney U test with the Bonferroni correction. Marginal discrepancies between prefiring and postfiring procedures were evaluated using the Wilcoxon signed-ranks test (alpha = .05). RESULTS: Significant differences in the marginal discrepancies of electroformed metal copings without porcelain and metal-ceramic crowns were found among all groups. The lowest range of median marginal discrepancy values (P < .05) at 4 sites, both before and after firing, occurred with the deep chamfer preparation (17.64-21.78 microm and 23.96-25.72 microm, respectively). The highest range values were observed in the shoulder preparation (38.13-49.89 microm and 73.87-89.44 microm, respectively). In all situations, the marginal discrepancies of the postfiring procedures were significantly greater (P = .02 or less) than those of the prefiring procedures. CONCLUSION: Within the limitations of this study, the marginal adaptation of electroformed metal copings or metal-ceramic crowns is affected by finish line design and sequentially diminished by porcelain firing procedures.
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