Long-Term Study Reveals Higher Complications for Cemented vs. Screw-Retained Zirconia Crowns on Dental Implants

The study led to the following findings:

• A total of 370 patients underwent randomization; 189 and 181 were assigned to the voltage (underwent voltage-guided PVI) and control (underwent conventional LSI-guided PVI) groups, respectively.
• The primary efficacy endpoint occurred in 12.0% of patients in the voltage group and 12.9% in the control group (1-year Kaplan–Meier event-free rate estimates, 88.0%, and 87.1%, respectively; hazard ratio, 1.00).
• The primary safety endpoints were 4.8% in the voltage group and 6.6% in the control group.
• PVI time was significantly shorter in the voltage group (35.7 ± 14.5 min versus 39.7 ± 14.7 min).

The 7.5-year follow-up data on the biological and technical outcomes of screw-retained and cemented all-ceramic implant-supported single crowns on zirconia abutments revealed the following: (1) both types of restorations experienced a high rate of major technical and biological complications, leading to (2) reduced survival rates for the crowns; and (3) a significant increase in bleeding on probing in the cemented group, while the screw-retained group did not show a similar increase.

The study's main limitations include the inclusion of premolar sites, which may have led to higher abutment fractures, and the small sample size (44 patients) with a 6.8% dropout rate. The significant rise in complications, including fractures, by the 7.5-year mark underscores concerns about using one-piece zirconia abutments.

Reference:

Kraus, R. D., Hjerppe, J., Naenni, N., Balmer, M., Jung, R. E., & Thoma, D. S. A 7.5-year randomized controlled clinical study comparing cemented and screw-retained one-piece zirconia-based implant-supported single crowns. Clinical Oral Implants Research. https://doi.org/10.1111/clr.14346