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Comparison of the marginal fit of different all-ceramic and metal-ceramic crown systems: an in vitro study

STATEMENT OF PROBLEM: High levels of fracture resistance offered by today's ceramic crown systems might eliminate the need for adhesive cementation. However, high accuracy of fit involving gap widths <75 µm is also required for conventional cementation.

PURPOSE: This in vitro study was performed to evaluate six ceramic crown systems for their accuracy of fit.

MATERIAL AND METHODS: A total of 60 experimental crowns were fabricated from four all-ceramic systems (Vita Mark II/Cerec 2, IPS Empress/staining, Vita In-Ceram Alumina/Cerec 2, and Procera All-Ceram) and two metal-ceramic systems (electroformed or conventional copings). All restorations were delivered to prefabricated stone dies with conventional zinc-phosphate cement. Gap widths were measured by light microscopy (magnification ×200). Intergroup differences were analyzed by one-way ANOVA. Kolmogorov–Smirnov test was used to evaluate normal distribution plots and box plots of different measurements within each group.

RESULTS: Marginal gaps averaged 142.3 µm for Vita Mark II, 109.3 µm for IPS Empress, 98.1 µm for Vita In-Ceram Alumina, and 47.3 µm for Procera All-Ceram. Galvano-ceramic and metal-ceramic restorations yielded 68.5 and 77.5 µm. Differences reached statistical significance for Vita Mark II versus all other systems except IPS Empress; for galvanic restorations versus Vita Mark II and IPS Empress; and for Procera All-Ceram versus all other all-ceramic systems.

CONCLUSIONS: The incorporation of all ceramic crowns requires different ways of cementation, depending on the marginal gap. This in vitro study showed that Procera All-Ceram crowns can be conventionally cemented with zinc-phosphate cement.

CLINICAL IMPLICATIONS: Procera All-Ceram crowns offer marginal gap widths well below 75 µm. Therefore they can be cemented with conventional zinc-phosphate cement. Different cementation techniques are strongly recommended for all other all-ceramic systems tested.

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