Evaluation of the marginal accuracy of different all-ceramic crown systems after simulation in the artificial mouth

The in vitro marginal fit of five different all-ceramic crown systems (In-Ceram(R), Empress(R) staining technique, Empress(R) veneering technique, Celay(R) feldspathic system, Celay In-Ceram(R) system) was evaluated before and after cyclic preloading in an artificial mouth. The crowns were adhesively luted to extracted natural maxillary incisors prepared with a 90 degrees shoulder. The results were compared to those for porcelain-fused-to-metal (PPM) crowns with circular porcelain-butt margins which were cemented with zinc phosphate cement. The analysis of the marginal discrepancies showed significant (P<0.001) differences among the groups. Crown cementation increased the marginal gaps significantly (P < 0.01). Empress(R) staining technique crowns showed the smallest marginal gaps (median 47 mu m), followed by conventional InCeram(R) crowns (median 60 mu m) and Empress(R) veneer technique crowns (median 62 mu m). Celay In-Ceram(R) crowns displayed marginal openings with a median of 78 mu m, followed by Celay(R) feldspathic crowns with a median of 99 mu m. The marginal gap of the PFM control crowns showed a median of 64 mu m. Ageing in the chewing simulator had no significant influence on the marginal fit of all specimens. The study indicates that all the tested all-ceramic crowns have clinically acceptable margins. However, in vivo investigations of all all-ceramic crown systems should be made before clinical routine.