## 4 Discussion  
The objective of this retrospective clinical cohort study was to evaluate, at 18 months of follow-up, the implant survival rate, marginal bone loss, peri-implant parameters, surgical and prosthetic complications of immediately loaded post-extractive implants in single or partial implant-prosthetic rehabilitations. The implant survival rate was 95.92%. Implant failure was statistically associated with smoking, systemic pathology, and site of implant placement, with the greatest loss of fixtures recorded in the posterior upper jaw. This result is consistent with the data reported by [PERSON] et al. in their retrospective 5-year follow-up clinical study of immediately loaded post-extractive implants. The study included 45 patients treated with rough surface implants, and the survival rate of 97.8% confirmed the long-term reliability of post-extractive implants [20]. In addition, [PERSON] et al. performed a systematic review and meta-analysis of 292 studies that evaluated a total of 35,511 implants in smokers and 114,597 implants in non-smokers. The analysis showed that the rate of implant failure in smokers was statistically higher than in non-smokers, with reduced implant stability and increased marginal bone loss [21]. Similarly, [PERSON] et al. conducted a review of 34 studies, showing that smoking is a primary risk factor for implant failure, regardless of implant site and type of load applied [22]. Regarding peri-implant marginal bone loss, logistic regression showed a significant association between MBL and implant site, smoking, and the presence of systemic diseases, while no significant correlation was found with the type of rehabilitation. [PERSON] et al. conducted a prospective clinical study of 45 patients undergoing single post-extraction implants with immediate loading. The study used standardized digital radiographs to monitor the MBL and showed an average marginal bone loss of 0.35 mm at one year, with a more significant impact on smokers than on non-smokers [23]. [PERSON] et al. conducted a retrospective study on a cohort of 150 patients with a 5-year follow-up, evaluating peri-implant bone loss in relation to various risk factors. The analysis revealed that smoking, uncontrolled diabetes, and posterior implant sites were significantly associated with greater marginal bone loss. Specifically, diabetic patients exhibited a mean marginal bone loss (MBL) of 1.2 mm at 5 years compared to 0.8 mm in non-diabetic patients [24]. [PERSON] et al. conducted a clinical-radiographic study on 80 patients, comparing marginal bone loss between immediately loaded and delayed-loaded implants. The results indicated that immediately loaded implants exhibited a mean MBL of 0.85 mm at 12 months compared to 0.72 mm in delayed-loading implants; however, this difference was not statistically significant. Nevertheless, in patients with systemic conditions, marginal bone loss was significantly greater, suggesting, in agreement with the findings of the present study, a negative impact of systemic conditions on the long-term stability of implants [25]. Regarding peri-implant parameters, the probing pocket depth (PPD) was significantly higher in the posterior maxilla and was notably influenced by smoking, whereas no significant associations were observed with the type of rehabilitation or the presence of systemic conditions. The plaque index (PI) and bleeding on probing (BoP) showed a statistically significant increase over time, with the highest values recorded in the posterior maxilla and posterior mandible. Smoking was significantly correlated with both parameters, whereas no significant correlation was found with the type of rehabilitation or the presence of systemic conditions. Suppuration was documented in two patients and was significantly associated with smoking and systemic conditions, while no correlation emerged with the implant site or the type of rehabilitation. [PERSON] et al.