Objectives: To evaluate the long-term clinical outcomes of quad zygomatic implants (ZIs) as a rescue therapy for patients with failed full-arch implant rehabilitation in the maxilla due to advanced peri-implantitis.
Material and methods: This was a retrospective cohort study of all patients treated with the Quad Zygoma Protocol. Primary outcomes included the ZI survival and success rates, and secondary outcomes, the prosthetic success rate and complications.
Results: The study population included 28 consecutive patients who received 112 ZIs between 2006 and 2024, with a mean follow-up of 8.2 ± 4.1 years. In 23 patients, a total of 113 failed conventional implants were removed, and 48 ZIs were immediately placed into the explantation sites. The ZI survival rate was 98.2%, with two ZIs requiring removal due to late complications. The implant success rate was 93.5%, and prosthetic success was achieved in 96.4% of cases. Sinusitis was diagnosed in 8 patients (28.5%) at a mean of 5.92 years postoperatively; all cases were successfully managed medically without implant loss. Soft tissue recession occurred in 9.8% of cases, while oroantral fistula and facial fistula were each observed in 0.9% of implants.
Conclusions: The Quad Zygoma Protocol may represent a reliable and predictable option for the rescue of failed maxillary full-arch implant rehabilitations. Despite a relatively high prevalence of sinusitis, favorable long-term clinical outcomes were achieved with appropriate management.
Objective: This study follows a 2-year evaluation to verify marginal bone remodeling (MBR) trends associated with different abutment designs.
Methods: A balanced, randomised, double-blind clinical trial with two parallel experimental arms. 68 implants were placed in 9 men and 12 women, 48.5% using the straight abutment and 51.5% the concave abutment. The primary variable was peri-implant tissue stability, measured by marginal bone loss (MBL) or gain (MBG) through digital radiology. Mixed linear regression models and Additive Generalized Additive Models were constructed to estimate MBR, simultaneously considering the variables abutment height, group, and time.
Results: At 24 months, linear mixed-effects regression models revealed that the concave abutment group exhibited significantly less MBL than the straight abutment group across mesial, distal, and average measurements (p = 0.006-0.026). Significant interactions between abutment type and time at 8 weeks and 6 months suggest early and sustained benefits of the concave design. At 24 months, this effect remained significant except in the mesial model (p = 0.072). Abutment height was positively associated with MBL, particularly in the straight group; however, in the concave group, greater height mitigated bone loss (p < 0.01).
Conclusion: Concave abutments demonstrated a potential advantage in reducing early marginal bone loss and promoting mid-term bone stability compared to straight abutments. Their design may enhance soft tissue adaptation, contributing to improved peri-implant bone preservation. While increased abutment height showed a protective effect in the concave group, these findings require confirmation. Further long-term studies are warranted to validate these results and clarify their clinical relevance.
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