Marginal integrity of two zirconia-based crowns before and after porcelain veneering

ABSTRACT

The marginal integrity of fixed restorations always is a major matter of concern for dental clinicians. Any cause of distortion, including veneering processes, in the marginal integrity is supposed to be detrimental for long-term success of fixed dental prostheses. The aim of this in vitro study was to compare the marginal adaptation of two different full ceramic restoration systems [Zirkouzahu and Cercon] and possible changes in marginal integrity following the multiple veneering process. Twelve all-ceramic crowns in the form of coping were fabricated on a pre-made standard metal die with finish line of shoulder preparation from two commercial systems Cercon_ and Zirkonzahn_. The specimens were not cemented. The Crown/Die discrepancy were measured by means of a precise stereo microscope [accuracy +/- 0.1 microm], at various points [n=12] selected along circumferential margin of the restorations. Same procedure was accomplished after applying the veneering porcelain. The mean gap dimensions were calculated and data were analyzed by multivariate [b] test. Mean marginal gap dimensions before and after veneering porcelain firing cycles, for Cercon_ were [59.67 +/- 13.46 microm] and [63.75 +/- 14.16 microm] and for Zirkonzahn_ were [65.81 +/- 24.37 microm] and [64.74 +/- 21.94 microm], respectively. Hotelling trace Multivariate[b] test method showed that the rate ofmismatching marginal integrity in two groups [Cercon_ and Zirkonzahn_] had no significant difference before and after porcelain firing [P>0.05]. Within the limitation of this study, the marginal integrity of both systems were seems to be within the clinically acceptable standard dimension, i.e. 120microm.The marginal gap of both all-ceramic systems were not affected by veneering porcelain firing cycles