A Retrospective Analysis on Marginal Bone Loss around Tilted and Axial Implants in Immediate-Loaded All-On-4 with a Long-Term Follow-Up Evaluation

Objectives: The aim of this retrospective study is to assess whether axial and tilted implants supporting All-on-4 prosthesis show any differences in terms of survival rate, success rate and marginal bone loss (MBL) after a long-term follow-up (mean 9 years). Material and Methods: One hundred and fifty-six implants were included in this study, 78 of which were tilted (Group A) and 78 were axial (Group B). MBL was measured after a mean time of 9 years on periapical radiographs. Success and survival rate were assessed with the Misch criteria. The prevalence of peri-implantitis was calculated. Statistical analysis was conducted to assess comparisons between groups. A Kaplan-Meyer analysis was carried out for the survival rate. Results: A total of 156 implants were analyzed. After a 9-year mean time follow-up, the survival rate was 96.2% in group A and 98.7% in group B; and the success rate was 80.8% in group A and 74.4% in group B. The mean MBL was 1.2 mm (IQR 0.6-1.8) in group A and 1.4 mm (IQR 0.9-2.1) in group B. No statistically significant differences were shown between the two groups (p < 0.05). Peri-implantitis occurred in 15 implants and was equally distributed between the two groups. Conclusions: This study shows that axial and tilted implants have similar success rates, survival rates and MBL values after a long-time follow-up, assessing the biological reliability of the prosthesis they supported. Peri-implantitis occurred equally between the two groups.