## 4 Discussion  
The findings of this systematic review indicate that the success and survival rates of post-extraction implants are influenced by the timing of loading, with variations observed between immediate, early, and delayed loading protocols. These differences suggest that the decision regarding when to load an implant may impact its long-term prognosis. Furthermore, the heterogeneity in implant outcomes appears to correlate with variations in short- and middle-term bone loss, underscoring the importance of monitoring bone remodeling over time. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Variables** & **[PERSON] et al., 2012 [26]** & **[PERSON] et al., 2018 [25]** & **[PERSON] et al., 2020 [24]** \\ \hline Patients (n) & 60 & 54 & 75 \\ \hline Withdrawals (n) & 5 & 0 & 6 \\ \hline Female gender (n, \%) & 35 (58\%) & 32 (59\%) & 38 (55\%) \\ \hline Age ranges (n, years) & range 25-94; m NS; SD NS & range 22–77; m NS; SD NS & range 19–72; m NS; SD NS \\ \hline Follow-up (n, months) & 12 & 12 & 120 \\ \hline Implants (n) & 55 & 172 & 69 \\ \hline \multirow{2}{*}{Type of loading (n)} & Immediate loading (26) & Immediate loading (61) & \multirow{2}{*}{Immediate loading (35)} \\  & Delayed loading (29) & Early loading (56) & Early loading (34) \\ \hline \multirow{3}{*}{Location in arch (n)} & Posterior maxilla (18) & \multirow{3}{*}{Maxilla (83)} & \multirow{3}{*}{Maxilla (44)} \\  & Posterior mandible (18) & & \\ \cline{1-1}  & Anterior maxilla (18) & & \\ \cline{1-1}  & Anterior mandible (1) & & \\ \hline \multirow{3}{*}{Complications (n)} & Immediate loading (1) & Immediate loading (1) & \multirow{3}{*}{Immediate loading (3)} \\  & Delayed loading (2) & Early loading (6) & Early loading (4) \\ \hline \multirow{3}{*}{Total bone loss (mm)} & Immediate loading (0.45) m & \multirow{3}{*}{Early loading (0.18) m 0.36;} & \multirow{3}{*}{Immediate loading (0.9) m 1.0; SD 0.8} \\  & Delayed loading (0.25) m 0.75; & & \\ \cline{1-1}  & SD 0.17 & & \\ \cline{1-1}  & & & \\ \hline \multirow{3}{*}{Implant failure (\(n\))} & Immediate loading (1) & \multirow{3}{*}{Immediate loading (0)} & \multirow{3}{*}{Immediate loading (0)} \\  & Delayed loading (2) & & \\ \cline{1-1}  & Delayed loading (0) & & \\ \hline \multirow{3}{*}{Survival (\%)} & Total: 95\% & Total: 99.4\% & \multirow{3}{*}{Total: 94.9\%} \\ \cline{1-1}  & Immediate loading: 96.6\% & & \\ \cline{1-1}  & Delayed loading: 93.3\% & & \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Descriptive comparison of the studies selected for the meta-analysis. Indeed, the data referred to mean peri-implant bone loss 12 months after loading are contradictory. While two studies found bone loss to be smaller in the case of delayed loading versus immediate loading of the implants (0.25-0.45 mm [22] versus 0.55-0.62 mm [17], respectively), two other publications reported the opposite (0.55-1.33 mm versus 0.19-0.65 mm for delayed and immediate loading, respectively) [10; 20]. Likewise, in another study involving the same 12-month follow-up period, in which bone loss was evaluated in implants loaded in post-extraction sockets and implants loaded before 6 weeks postsurgery, the values proved to be very similar in both groups (0.19 mm and 0.18 mm, respectively) [20]. In the case of the studies with a two-year follow-up period, the bone loss values after immediate and delayed loading were seen to be very similar in two publications: 1.02-1.06 mm [13] and 0.10-0.11 mm [26], respectively. However, discrepancies were again observed after follow-up intervals of 4-10 years. In effect, while one study [24] reported similar bone loss with each loading protocol, other authors obtained better results with immediate loading [19; 24] or with delayed loading [14; 15; 16]. It should be noted that none of the studies recorded statistically significant differences between the groups, however. The data obtained from the review of the different studies indicate that there were few complications related to the post-extraction implants and prostheses (\(n=70\), for a total of 1847 implants).