Evaluation of Marginal/Internal Fit of Crown Analysis Technique

 

Objectives:   To evaluate two technique used in analysis of marginal/internal fitting accuracy of crown.

Methods: Tooth #14 was prepared per standard specification to receive an all-ceramic crown restoration on Dentoform Typodont.  The preparation had well-defined, 1 mm circumferential shoulder gingival margin, 2 mm occlusal reduction, rounded internal angles, and less than 20° total occlusal convergence. Total thirty tooth #14 were duplicated and poured in dental stone type V. Duplicate tooth or die was placed in full-dentate typodont. Impressions were taken on the posterior left region area with two-step impression techniques using a custom triple tray with light and putty consistency VPS and sent to dental laboratories for fabricating the monolithic press lithium-disilicate crown. For impression technique (group1), crown was filled with light-body consistency VPS and placed on die with a constant force of 100N. After it set, crown was removed from the die while the thin VPS films representing the space between the die and the crown remain on the die. The thin VPS film was stabilized by a heavy body VPS (Imprint™ 3, 3M ESPE). In group2, same crowns were cemented using Multilink®Automix (Ivoclar Vivadent) under constant pressure of 100N. Samples were embedded in acrylic and sectioned buccolingually. Sections were evaluated under digital microscope and measured on 3 locations per buccal and lingual side of section: marginal-edge, mid-axial wall, and cusp-tip. Statistically analysis was accomplished with Kruskal-Wallis one-way ANOVA. Significance was predetermined at p<.05.

Results: Significant difference was found at lingual of mid-axial, buccal and lingual margins between groups.

	Buccal			Occlusal	Lingual
(µm±SD)	Margin	Mid-Axial	Cusp		Cusp	Mid-Axial	Margin
Group1	(104.8±64.39)*	(155.2±73.52)	(214.20±57.05)	(231.2±60.39)	(228.5±50.07)	(115.8±54.65)*	(94.41.9±52.9)*
Group 2	(39.34±40.09)*	(167.2±53.01)	(213.8±65.48)	(218.12±81.12)	(203.5±73.92)	(148.2±71.17)*	(49.06±45.75)*

<>Conclusions: The Impression technique measurement was not as accurate as the cemented technique when measuring the thin space cement layer.