Marginal Discrepancy of Monolithic and Veneered All-Ceramic Crowns on Titanium and Zirconia Implant Abutments Before and After Adhesive Cementation: A Scanning Electron Microscopy Analysis

Purpose: To evaluate the marginal discrepancy of monolithic and veneered all-ceramic crown systems cemented on titanium (Ti) and zirconia implant abutments. Material and Methods: Sixty customized implant abutments for a maxillary right central incisor were fabricated of Ti and zirconia (n = 30 of each) for an internal-connection implant system. All-ceramic crowns were fabricated using the following systems (n = 10 per group): monolithic with computer-aided design/computer-assisted manufacture (CAD/CAM) lithium disilicate (MLD), pressed lithium disilicate (PLD), or CAD yttrium-stabilized tetragonal zirconia polycrystal (Y-TZP). The frameworks of the PLD and Y-TZP systems were manually veneered with a fluorapatite-based ceramic. The crowns were cemented to their implant abutments, and the absolute marginal discrepancy of the gap was measured before and after cementation. Data were analyzed statistically. Results: Marginal discrepancies were significantly influenced by the crown system and by cementation, but the material did not significantly affect the results. Interaction terms were not significant. Y-TZP crowns on both Ti and zirconia abutments presented the smallest mean marginal discrepancies before (52.1 +/- 17 mu m and 56.2 +/- 11 mu m, respectively) and after cementation (98.7 +/- 17 mu m and 101.8 +/- 16 mu m, respectively). Before cementation, MLD crowns showed significantly larger mean marginal openings than PLD crowns on both Ti and zirconia abutments (75.2 +/- 12 and 77.5 +/- 13 mu m for MLD, 52.1 +/- 17 mu m and 69.7 +/- 8 mu m for PLD, respectively). After cementation, both Ti and zirconia abutments with MLD crowns (113.5 +/- 12 mu m and 118.3 +/- 14 mu m, respectively) showed significantly larger values than with PLD crowns (98.7 +/- 17 mu m and 109.4 +/- 9 mu m, respectively). Conclusions: Manually veneered Y-TZP crowns demonstrated more favorable marginal fit on both Ti and zirconia implant abutments before and after cementation compared to those of MLD and PLD.