## 4 Discussions  
This study compared the bone gain parameters (width and osteodensity) after the reconstruction of the mandibular implant sites by the S-GBR technique and two categories of xenografts (bovine-derived and porcine-derived), followed by an immediate implant placement. Strict inclusion and exclusion criteria of the subjects were applied in our study, as the selection criteria of the patients could maximize the success rate of the augmentation procedures [9]. Moreover, the S-GBR technique avoided postgrafting complications due to the improper stabilization of the grafting materials and of postoperative infections. The GBR techniques are highly recommended for bone defects requiring horizontal augmentation, while a meta-analysis found no statistically significant differences between the various horizontal augmentation techniques [19]. We performed an immediate implant placement with simultaneous augmentation procedures, as the literature data report similar implant survival rates for immediate and delayed implant placements [20]. The survival rate of implants in the control and test groups was 100% at 6 months follow-up. The implant survival rate in the implant sites reconstructed by lateral ridge augmentation ranged from 97% to 100% at 6-12 months of follow-up [21]. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & \multirow{2}{*}{**Group**} & \multicolumn{3}{c}{**Shapiro–Wilk Test**} & \multicolumn{3}{c}{**Mann–Whitney/**} \\ \cline{3-6}  & & **Statistics** & **Sig. \(p\)** & **U/t Student** & **Sig. \(p\)** \\ \hline WIDTH– & Control & 0.938 & 0.045 * & 738,000 & 0.156 \\ \cline{2-6} Bone gain & Test & 0.890 & 0.000 ** & & \\ \hline OSTEODENSITY– & Control & 0.823 & 0.000 ** & 896,000 & 0.972 \\ Bone gain & Test & 0.964 & 0.125 & & \\ \hline \hline \end{tabular}
* Statistically significant, \(p<0.05\); ** Statistically highly significant, \(p<0.01\).  
\end{table} 
Table 4: Mann–Whitney test. Intergroup statistical comparisons (control vs. test group). (Bone gain: height, width, osteodensity). Figure 4: **(a,b)** Intergroup comparisons of bone gain (width, osteodensity) at 6 months follow-up. (S-GBR + bovine-derived xenograft group vs. S-GBR + porcine-derived xenograft group.). Suggestions were made for the complete replacement of the xenografts with autologous bone in the implant sites with medium and severe alveolar resorption [22]. However, we performed the augmentation procedures with a combination of autologous bone and xenografts in both the control group (bovine xenograft) and the test group (porcine xenograft) due to the limits of the autogenous bone as a unique graft material (i.e., morbidity at the donor site, lower availability, and dehiscence risk of the wound) [23]. Moreover, some patients prefer nonautogenous bone grafts with fewer postoperative healing days, less pain, and a shorter recovery time [24]. Xenografts have many benefits when used in guided bone regeneration techniques due to their biocompatibility, osteoconduction, the low resorption rates, as well as their ability to maintain the volume of the regenerative compartment [25]. Porcine-derived bone graft materials have been recently promoted as alternative materials to autogenous bone in augmentation procedures due to their good physicochemical properties, high biocompatibility, their osteoconductive properties, and the development of different formulations that stimulate bone regeneration processes [26; 27]. Bone gains were recorded at 6 months follow-up in both groups of implant sites (control and test groups) for both measured parameters (width and osteodensity). The mean values found in our study for bone gains following the augmentation procedures and the immediate implant placement (S-GBR + bovine-derived xenograft vs. S-GBR + porcine-derived xenograft) are as follows: width (4.107 mm vs. 4.1624 mm); osteodensity (276.83 HU vs. 254.24 HU).