Evaluation of the intaglio surface trueness and fit of zirconia crowns fabricated using different machining strategies with a chairside CAD/CAM system.

AIM: The present study aimed to evaluate the intaglio surface trueness and fit of zirconia crowns depending on the different machining strategies used with the Cerec system. MATERIALS AND METHODS: Thirty duplicate tooth models for a single zirconia crown were randomly assigned to three groups (n = 10) according to the machining mode used for fabrication: grinding, wet milling, and dry milling. The scan data of the final crowns were compared with their design data to evaluate the intaglio surface trueness. The marginal and internal fit were evaluated using a cross-sectional method. The time required for the machining and sintering processes was measured for each group. RESULTS: The wet-milling group showed better trueness (root mean square: 13.8 +/- 1.0 mum) than the grinding and dry-milling groups (P < 0.001). The marginal gap was greater in the grinding group (58.6 +/- 28.9 mum) than that in the wet- and dry-milling groups (P < 0.001). The dry-milling group required the shortest time for the manufacturing process. CONCLUSION: All machining modes fabricated crowns with a clinically acceptable trueness and fit. However, the dry-milling mode was advantageous for the chairside CAD/CAM system with respect to time efficiency.