Evaluation of fit of zirconia posterior bridge structures constructed with different scanning methods and preparation angles

This study evaluated the influence of scanning method, abutment position, and preparation angle on the vertical seal of three-unit posterior zirconia structures. Sixty differently angled metallic models were machined to receive 30 bridge frameworks. For each preparation type, half of the structures were waxed-up and digitized, whereas the other half were computer-designed after the abutments were scanned. Once milled, the samples were cemented in standard fashion. Misfit was assessed by scanning electron microscopy. Three-way analysis of variance showed significant differences. Computer-designed structures achieved the highest accuracy (P < 0.0001). No significant differences were recorded concerning the abutment position and convergence angle. All discrepancy values were within the clinically acceptable range.