Figure 1 shows the flow diagram of the study. A total of 1532 records were found after the primary search, and after removing duplicates, 909 studies remained. After the primary and final screening toward the inclusion and exclusion criteria, 26 articles were included in this review. Among all these studies, 21 articles were considered for the qualitative and quantitative analysis.

PRISMA flow diagram of the study

Among all included studies, 19, 1, 4, 1, 2, and 16 treatment arms were available on CTG, a combination of CTG with platelet-rich fibrin (L-PRF), Mucoderm, Mucograft, AlloDerm, and No Treatment, respectively. Moreover, from the included studies, two of them [27, 28] and four of them [16, 30, 32] were performed and reported on the same populations. The methodological characteristics of the included studies are summarized in Table 1.

This systematic review pooled 530 immediate implants placed. Soft tissue grafts were applied in 320 implant placements; CTG was used in 238, CTG + L-PRF was used in 6, porcine-derived collagen matrices in 51 (43 Mucoderm and 8 Mucograft), and acellular dermal matrices (AlloDerm) in 25. Furthermore, bone graft was used in 434 immediate implant placements. It was mentioned in the included studies, except Abd El-Aziz et al. study [25], that implants replaced teeth ranging from 1 to 5, maxillary anterior or premolar regions. All implant types were bone level.

Implants with different widths, ranging from 3.2 to 5 mm, and lengths, ranging from 9 to 18 mm, were employed, respectively. Nine studies did not mention the diameter width of implants [17, 20, 21, 23, 24, 27, 28, 32, 35] and nine did not mention the length of implants [17, 21, 23, 24, 27, 28, 32, 34, 35].

Sixteen studies mentioned the type of restorations used; all were non-splinted single crowns as in 11 studies were screw-retained [16, 21, 25, 27,28,29,30, 32,33,34, 36] and 11 studies cement-retained [16, 17, 19, 20, 22, 29,30,31,32,33,34].

Various follow-up periods with different onset times were observed in studies ranging from 2 weeks to 5 years.

Thirteen studies reported on the insertion torque of the implants [16,17,18, 20,21,22, 24, 29,30,31,32, 34, 36] employing different methodologies for reporting ranging between 20 to 48.55 N-cm.

The overall quality assessment of the studies is summarized in Fig. 2. None of the studies exhibited a high risk of bias. Randomization process was the most problematic domain among all domains due to the lack of a clear allocation concealment process, and 10 studies raised some concerns regarding this issue [16, 18, 21, 27, 28, 31,32,33,34, 36]. Five studies raised some concerns due to deviations from intended intervention (D2) [21, 28, 31, 32, 36]. There was only one study showing some concerns missing outcome data (D3) [25] and in measurement of the outcome (D4) [16]. Selection of the reported results (D5) was the only domains that raised no concerns in the included studies. In summary, among the 21 included studies, 11 showed an overall some concerns regarding bias [16, 18, 21, 25, 27, 28, 31,32,33,34, 36] While the 10 others demonstrated an overall low risk of bias [17, 19, 20, 22,23,24, 26, 29, 30, 35]. Moreover, an outcome specific assessment of the risk of bias are presented in the Appendix S1 as Figs. 1/S1, 2/S1, 3/S1, 4/S1, 5/S1, 6/S1, 7/S1 correspond to assessment of the risk of bias concerning studies reporting PES, MIBL, BBT, KTW, STT, PH, and MGML.

Summary of the included studies’ overall risk of bias

Table 2 summarizes the PES/WES, MIBL, BBT, KTW, STT, PH, MGML, and the complications experienced in the studies.

Twelve studies [16, 19, 20, 22,23,24,25, 27, 32,33,34,35] analyzed mean PES in using grafts and no grafts groups, reporting all studies no significant difference between them. Two studies [