Clinical marginal and internal gaps of In-Ceram crowns fabricated using the GN-I system.

The marginal and internal gaps of ceramic crowns with alumina copings fabricated using a computer-aided design, computer-aided manufacturing system, were evaluated in vivo using silicone materials. Black and white silicone materials were used to record the marginal and internal gaps of 82 In-Ceram crowns before final cementation. The silicone materials were sectioned bucco-lingually and mesio-distally and viewed under a microscope to measure the thickness of the white silicone layer. Sixteen reference points were measured on each specimen. The mean marginal gaps were compared among the anterior, premolar and molar teeth, and the mean gaps at the reference points within the groups were compared by analysis of variance and the Dunnett T3 test. The mean marginal gap was 66.8 mum. There were no differences in marginal gaps among the three groups. In all the groups, the marginal gaps were the smallest, whereas the occlusal gaps were the largest. The mean marginal gaps of the In-Ceram crowns with the alumina copings fabricated using the GN-I system were within the range of clinically acceptable values.