Clinical performance and fit of a milled ceramic crown system

Objective: To assess marginal accuracy and clinical performance of a new lithium-disilicate crown system.

Method: A new all-cermaic crown system (e-max cad, Ivoclar) based on a lithium disilicate milled coping veneered with porcelain, was assessed for marginal accuracy and clinical performance. A total of 14 volunteers were treated with 31 crowns (23 anterior, 8 posterior) by two operators. All crowns were cemented with resin cement (Multilink, Ivoclar). Before placement, all crowns were evaluated for marginal accuracy on their respective dies at 4 aspects (M,D,F,L) under a measuring microscope. Subjects were recalled for observation after 6 months and at yearly intervals. Restorations were evaluated for clinical fit and appearance at time of placement. Recall evaluation parameters included: marginal fit, appearance, retention, gingival health, porcelain fractures, plaque retention, marginal decay, pulpal problems (requiring RCT).

Results: Mean in-vitro marginal fit was 67.92 (+/-25.2) µ. Clinical fit was ranked Alpha for all restorations. 3 anterior single crowns required re-fabrication for improved color. 17 restorations (55% of all) were evaluated at 2-3 yrs. Only one (posterior) restoration fractured after requiring RCT through the crown. A list of # of restorations at last recall and findings is shown below.   

Last recall	6 months	12 months	24 months	36 months
# of crowns	8	6	11	6
Adverse findings		1 RCT, 1 fracture

   Conclusions: The new crown system tested exhibited excellent fit and appearance at time of placement. Except for one posterior restored tooth requiring RCT and subsequent crown fracture (3.2% of total crowns), no adverse findings were noted throughout the recall process so far.

(This study was supported by a grant from Ivoclar)