## 3 Results  
As shown in Figure 1, a total of 273 articles were found by electronic and hand search. After eliminating the duplicated and the ineligible studies, 31 studies were elected by title and abstract. Twenty-one articles were reviewed. This review investigated the studies which were primarily concerned with comparing the effect of bone-level or tissue-level design on MBL around implants. According to the inclusion/exclusion criteria, 17 articles with a total of 1.895 implants were included [38; 39; 40; 41; 42; 43; 44; 45; 46; 47; 48; 49; 50; 51; 52; 53; 54]. Eight studies compared bone and tissue level [35; 39; 45; 46; 47; 48; 49; 50]; seven articles studied bone-level implants [38; 40; 41; 44; 45; 46; 47], while two articles studied tissue-level implants [42; 48]. It is noteworthy to mention that five articles, when read in full text, did not strictly compare bone-level with tissue-level implants, but we included them because they provided data of interest for this review [44; 45; 46; 47; 48] (Figure 1, Table 1). Figure 1: Flow chart. \begin{table}
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**Authors** & **Study Design** & **Sample** & **Impal System, Brand and Number** & **Impal Length and Diameter** & **Surgery** & **[Follow-Up] Methods of Measurements** & **Survival Rate \& **Results (mean MRL, CRH, HRL ORH) in mm. ** & **Covariates** \\ \hline \hline \multirow{4}{*}{ \begin{tabular}{} \end{tabular}  } & \multirow{4}{*}{ \begin{tabular}{} \end{tabular}  } & \multirow{4}{*}{ \begin{tabular}{} \end{tabular}  } & \multirow{4}{*}{ \begin{tabular}{} \end{tabular}  } & \multirow{4}{*}{ \begin{tabular}{} \end{tabular}  } & \multirow{4}{*}{ \begin{tabular}{} \end{tabular}  } & \multirow{4}{*}{ \begin{tabular}{} \end{tabular}  } & \multirow{4}{*}{\ \begin{tabular}{} \end{tabular}  } & \multirow{4}{*}{ \begin{tabular}{} \end{tabular}  } \\  & & & & & & & & & \\ \cline{1-1} \cline{6-10}  & & & & & & &  
\begin{table}
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**Authors** & **Study** & **Study** & **Sample** & **Impat System,** & **Impat Length** & **Impat Length** & **Methods of** & **Survival Rate \& \& **Results (mean** & **MBL, CRL, HELL** & **Covariate** \\  & **Design** & **Number** & **(mm)** & & & & **Measurements** & **Success Rate** & **OR FILL) in mm. ** & & - & -  
Patient (P), Implant (I), Month (m), Female (F), Male (M), Implants were inserted with a full-thickness periosteal flap elevation approach or flapless in post-extractive sites (Technique A), Implant was placed post extraction with GBR (Technique B), Post extraction of 6-months healing (Technique C), Survival rate (SVR), Success rate (SCR), Marginal bone loss (MBL), Peri-implant bone loss (PIL), Crestal bone loss (CBL), None reported (NR), Bone level (BL), Tissue Level (TL) Bone level inserted 0.75-1 mm above the crest (SC), 0.75-1 mm above the alveolar crest (SC), High bone loser (HBL), Narrow-diameter implants (NDIs), Regular-diameter implants (RDIs), Peri-implant probing depth (PD), Note Mentioned (N.m), Soft tissue level (STL), Bone level (BL), Maxilla (MAX), Mandible (MAN), Bleeding on probing (BOP), Pink esthetic score (PES), White esthetic score (WES), Periapical X-ray (Px), Panoramic X-ray (Pan), Intraoral Radiographs (Int), Randomized Clinical Trial (RCT)  
Eight studies compared the MBL around dental implants placed at bone level and tissue level [39; 43; 49; 50; 51; 52; 53; 54], with a total of 684 implants. Bone-level implants in these studies had mean MBLs (of 0.12 \(\pm\) 1.47 mm, 0.97 \(\pm\) 0.64 mm, infra crestal 0.09 \(\pm\) 0.16, crestal 0.90 \(\pm\) 1.09, 0.17 \(\pm\) 0.017 mm, 0.93 \(\pm\) 0.37 mm, 0.83 \(\pm\) 0.58 mm, 1.324 \(\pm\) 0.64 mm, 0.18 \(\pm\) 0.46 mm) over a total of 341 implants. The average mean of each study was 0.795 mm, 0.805 mm, 0.125 mm, 0.995 mm, 0.17 mm, 0.65 mm, 0.705 mm, 0.982 mm, and 0.32 mm.