## 4 Discussion
Nevertheless, peri-implant mucositis stood out as the most common complication. This reversible inflammatory response of the soft tissues surrounding the implant may lead to peri-implantitis and implant failure if not properly diagnosed and treated [21; 25]. On the other hand, it should be mentioned that although none of the studies related the complications to the implant success-survival rate, the data indicate that regardless of the post-extraction implant loading protocol used and the duration of follow-up, the reported survival rates were between 90.3-100%, which is consistent with the data found in the literature [4; 5; 6; 7]. Prosthetic complications and the type of implant-abutment connection are essential factors in the long-term success and stability of post-extraction implants. Different connection types, such as internal versus external connections, have been associated with varying levels of mechanical stability, risk of micro-movements, and bacterial infiltration, all of which can impact peri-implant tissue health and the incidence of complications. Studies suggest that internal connections may reduce the risk of screw loosening and enhance load distribution, potentially minimizing prosthetic complications. Future investigations should consider these variables to better understand their impact on the prosthetic outcomes of post-extraction implants and provide guidance on optimal connection choices for enhancing implant longevity and minimizing complications [18; 20; 21; 25; 26; 27; 28]. The following conclusions can be drawn from the qualitative analysis: (a) the appropriate timing of functional loading of the implant to ensure minimum peri-implant bone loss is not sufficiently clear; (b) complications are few and generally manifest in the first year after implant loading, with no clear differences between the different loading protocols; (c) the short-, middle-, and long-term survival rates are similar with immediate, early, and delayed implant loading. With regard to the quantitative findings of the present study, the meta-analysis showed peri-implant bone loss in post-extraction implants to fall within ranges traditionally considered to be tolerable. In this respect, it has been considered normal and unavoidable to expect a bone loss of 1.5 mm around the implant in the first year of loading, and of 0.1 mm over the following years [27; 28; 29], though it is now recognized that initial marginal bone loss rates of over 0.1 are indicative of the progression of bone loss and a consequent risk of peri-implantitis [30; 31], as described in previous reviews and meta-analyses [5; 32; 33]. In general, peri-implant bone loss is associated with factors related to the patient (disease conditions, bone quality, habits), the implants (material, surface, design, dimensions) and surgery (technique, implant placement, and surgeon experience) [27], and these variables have not been considered in the present study or quantitatively evaluated in the articles selected for the meta-analysis. In this regard, it can be assumed that the complications (implant mobility, infection, mucositis) reported in two of the reviewed studies can be explained by the fact that the final bone loss values were >0.44 mm in immediate and delayed loading [22] and early loading [16]. In any case, the final total values suggest that peri-implant bone loss is less pronounced when the post-extraction implants undergo delayed loading versus immediate and early loading, over follow-up periods of 12 months [18; 22] and 10 years [16]. These results are in contrast to those obtained in other reviews and meta-analyses. One such study reported no statistically significant differences in comparing bone loss in post-extraction implants subjected to immediate loading versus implants subjected to early and conventional loading [30], while another publication failed to obtain sufficiently convincing evidence of clinically important differences in bone loss according to the timing of post-extraction implant loading [8].