Mechanical Stability of Zirconia Meso-abutments Bonded to Titanium Bases Restored with Different Monolithic All-Ceramic Crowns

Purpose: To evaluate the bending moments and failure modes of zirconia meso-abutments bonded to titanium bases restored with different monolithic all-ceramic crowns after aging, and to compare them to titanium abutments restored with all-ceramic crowns. Materials and Methods: Forty-eight internal conical connection implants (CONELOG, Camlog Biotechnologies GmbH 4.3 mm diameter) were restored with four different computer-aided design/computer-aided manufacturing (CAD/CAM) abutment-crown combinations (n = 12). Thirty-six customized zirconia meso-abutments were bonded to titanium bases (CONELOG Titanium Base CAD/CAM crown, Camlog Biotechnologies GmbH) and divided into three groups according to the different crown materials: (T1) monolithic lithium disilicate (e.max CAD, Ivoclar), (T2) monolithic PICN (polymerinfiltrated ceramic network [Enamic, Vita]), and (T3) monolithic zirconia (Lava Plus, 3M ESPE). Twelve titanium customized abutments restored with monolithic lithium disilicate (e.max CAD, Ivoclar) crowns served as the control group (C). The crowns were equal maxillary central incisors and were adhesively bonded with a resinbased cement (Panavia 21, Kuraray). All samples were embedded in acrylic holders. After aging (1,200,000 cycles, 49 N, 1.67 Hz, 5°C to 50°C, 120 seconds), static load was applied until failure. Bending moments were calculated for comparison of the groups. Data were statistically treated with one-way analysis of variance (ANOVA) followed by Tukey post hoc test (P .05). Failure modes were analyzed descriptively. Results: The means of the bending moments were 356.4 ± 20.8 Ncm (T1), 357.7 ± 26.3 Ncm (T2), 385.5 ± 21.2 Ncm (T3), and 358.8 ± 25.3 Ncm (C). Group T3 revealed significantly higher mean bending moments than the other groups (P .05). No differences were found between zirconia meso-abutments supported by titanium bases and customized titanium abutments when lithium disilicate crowns were used (P > .05). No failures were identified during and after aging. After static load, failures occurred due to fracture of the abutment in the internal connection in all the groups. Conclusion: Zirconia meso-abutments bonded to titanium bases showed similar mechanical stability compared with customized titanium abutments. Regarding the crown material, all three tested ceramics (lithium disilicate, PICN, and zirconia) revealed very good stability when used in the monolithic state. Keywords: aging, bending moments, CAD/CAM, monolithic crowns, titanium base, zirconia abutments