Clinical fit of four-unit zirconia posterior fixed dental prostheses

The objective of this clinical study was to assess the internal and marginal accuracy of computer-aided design/computer-aided manufacturing (CAD/CAM)-generated four-unit all-ceramic posterior fixed dental prostheses (FDPs). The data were compared with the results of three-unit metal-ceramic and all-ceramic FDPs that were obtained in a previous study. Twenty-four patients were provided with all-ceramic posterior four-unit FDPs made from semisintered blank zirconia material. Prior to definitive insertion the accuracy was evaluated using a replica technique with a light body silicone that was stabilized with a heavy body material. The replica samples were examined using microscopy. The median marginal gap of the 24 four-unit FDPs was 77 mum. The median gap widths were 87 mum at the midaxial wall, 167 mum at the axio-occlusal transition of the abutments, and 170 mum at centro-occlusal location. Although the marginal accuracy of the four-unit FDPs differed significantly from that of the three-unit metal-ceramic FDPs (median 54 mum), the values obtained were clinically satisfactory and showed that semisintered zirconia blanks could be used for the fabrication of four-unit FDPs.