Abstract
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.
Highlights
Implant-supported prosthesis have been used for many years in order to rehabilitate full-edentulous patients, and their validation is well reported through scientific literature [1,2]
The first evolution of this technique can be found in a paper published by Krekmanov et al The distal, tilted implants allowed for better prosthetic support and the placing of longer implants with better bone anchorage, suitable conditions for immediate loading [3]
As previously said, placing tilted implants in the inter-foraminal area allows for the avoidance of major bone regenerations; maxillary distal implants are tilted in proximity of the mesial wall of the maxillary sinus, taking advantage of the cortical bone to obtain stability and direction; mandibular distal implant inclination avoids the emergence of the nerve and the possible presence of a loop
Summary
Implant-supported prosthesis have been used for many years in order to rehabilitate full-edentulous patients, and their validation is well reported through scientific literature [1,2]. A definitive protocol that combines these concepts consists of the All-on-4 technique, first proposed by Malo to rehabilitate the mandible and later the upper jaw [6,7] This technique made it possible to diminish the number of implants utilized, decreasing distal cantilever and aiming to reduce prosthetics complications [8]. Whilst tilted implants did not demonstrate increased bone stress outside physiological levels when compared to axial implants, they showed significant biomechanical advantages [10,11] Considering that this technique is still relatively recent, the aim of this study was to investigate the value of marginal bone loss (MBL), along with the survival and success rate, and the occurrence of peri-implantitis on implants placed with the All-on-4 technique
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