## 3 Results
### Comparative Analysis  
Regarding the quantitative analysis, seven studies [41; 43; 49; 51; 52; 53; 54] evaluated the MBL between bone-level and tissue-level implants. Forest plots were produced to represent it graphically (Figure 2). The difference in MBL between bone-level implants and tissue-level implants was statistically significant, with a greater loss of bone in bone-level implants (Mean Difference: 0.11, 95% CI:0.02 to 0.19, \(p\) = 0.01, and I2 heterogeneity: 81%, \(p\) < 0.0001). Figure 2.  
### Comparative Analysis  
Regarding the quantitative analysis, seven studies [41; 43; 49; 51; 52; 53; 54] evaluated the MBL between bone-level and tissue-level implants. Forest plots were produced to represent it graphically (Figure 2). The difference in MBL between bone-level implants and tissue-level implants was statistically significant, with a greater loss of bone in bone-level implants (Mean Difference: 0.11, 95% CI:0.02 to 0.19, \(p\) = 0.01, and I2 heterogeneity: 81%, \(p\) < 0.0001). Figure 2.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & \multicolumn{2}{c}{**Solee Level**} & \multicolumn{2}{c}{**Tissue Level**} & \multicolumn{2}{c}{**Mean Difference**} \\
**Study or Subgroup** & **Mean** & **SD** & **Total** & **Weight** & **IV, Fixed, 95\% CI** \\ \hline [PERSON] et al. 2021 & 0.83 & 0.58 & 18 & 0.38 & 0.46 & 25 & 6.93 & 0.45 [0.13, 0.77] \\ [PERSON] et al. 2022 & 0.9 & 1.9 & 10 & 0.22 & 0.35 & 10 & 0.56 [0.18–0.52, 1.88] \\ [PERSON] et al. 2019 & 0.14 & 0.11 & 50 & 0.18 & 0.46 & 50 & 42.0–0.04 [-0.17, 0.09] \\ [PERSON] et al. 2016 & 0.12 & 1.47 & 49 & 0.04 & 1.3 & 99 & 3.16 & 0.08–0.40, 0.56 \\ [PERSON] et al. 2018 & 0.93 & 0.37 & 10 & 0.28 & 0.21 & 10 & 10.44\% & 0.65 [0.39, 0.91] \\ [PERSON] et al. 2020 & 0.97 & 0.64 & 97 & 1.18 & 0.89 & 43 & 8.30–0.21–0.50, 0.08 \\ [PERSON] et al. 2023 & 1.324 & 0.64 & 76 & 1.194 & 0.3 & 80 & 28.8\% & 0.13 [-0.03, 0.29] \\ \hline \multicolumn{10}{l}{**Total (95\% CD)**} & **310** & **317** & **100.0\%** & **0.11** [0.02, 0.19] \\ \multicolumn{10}{l}{Heterogeneity: Ch\({}^{2}\) = 30.86, df = 6 (\(p\) < 0.0001); f = 81\%} & & & & \\ \multicolumn{10}{l}{Test for overall effect: Z = 2.49 (\(p\) = 0.01)} & & & & \\ \hline \hline \end{tabular}
\end{table}
Table 2: Quality evaluation of the articles according to the Jadad scale [35].  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline  & **Soleetion** & **Comparability** & **Exposure** & **Score (0–9)** \\ \hline [PERSON] et al. [38] & *** & * & ** & 6 \\ \hline [PERSON] et al. [39] & *** & * & ** & 6 \\ \hline [PERSON] et al. [40] & *** & * & ** & 6 \\ \hline [PERSON] et al. [41] & *** & * & ** & 6 \\ \hline [PERSON] et al. [43] & *** & * & ** & 6 \\ \hline [PERSON] et al. [44] & *** & * & ** & 7 \\ \hline [PERSON] et al. [45] & *** & * & ** & 6 \\ \hline [PERSON] et al. [46] & *** & * & ** & 7 \\ \hline [PERSON] et al. [47] & *** & * & ** & 6 \\ \hline [PERSON] et al. [48] & *** & * & ** & 6 \\ \hline [PERSON] et al. [49] & *** & * & *** & 7 \\ \hline [PERSON] et al. [52] & *** & * & ** & 6 \\ \hline [PERSON] et al. [53] & *** & * & *** & 8 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Quality assessment for case-control and cohort studies based on Newcastle–Ottawa Scale [37].  
Figure 2: Forest plot comparing MBL of tissue-level and bone-level implants [41; 43; 49; 51; 52; 53; 54].  
Only one study analyzed soft-tissue thickness, concluding that, the less soft tissue, the greater the marginal bone loss, with a 12-year control of 0.88 mm [44].