Clinical Bonding of Resin Nano Ceramic Restorations to Zirconia Abutments: A Case Series within a Randomized Clinical Trial

Background: New dental materials are introduced and promoted in the field without extensive clinical testing. Using those materials in a clinical setting might result in unacceptable early failure rates. Purpose: The purpose of this paper was to analyze bonding of a new dental restorative material to either zirconia stock abutments or zirconia customized abutments. Materials and Methods: Fifty participants seeking single implant treatment were included in a prospective study. Resin Nano Ceramic (RNC, Lava Ultimate, 3M ESPE, Seefeld, Germany) crowns were digitally manufactured and extraorally bonded to either a stock or a customized zirconia abutment (ZirDesign and ATLANTIS, DENTSPLY Implants, Molndal, Sweden) by means of a resin composite cement (RelyX Ultimate in combination with Scotchbond Universal, 3M ESPE), strictly following the manufacturer's recommendations. The final restorations were screw-retained to the implants and followed during 12 months. Primary outcome parameter was uncompromised survival of the restoration, and secondary outcome parameter was mode of failure. Results: No implants were lost. The uncompromised survival rate of the RNC crowns bonded to zirconia abutments after 1 year of clinical service was only 14% (n = 7). Catastrophic failure occurred in three cases (6%), whereas bonding failure between RNC crowns and zirconia abutments occurred in 80% of the cases (n = 40) within the first year of service. No statistical significant difference in uncompromised survival rate could be identified between abutment types (chi(2) = 1.495, p =.209). Uncompromised survival rate after 1 year was highly significantly different (chi(2) = 104.173, p <.001) from a reference standard, which was set at 95%. Conclusion: RNC crowns luted to stock and customized zirconia implant abutments with the particular resin composite cement in this trial have a poor prognosis, regardless of the abutment type used.