In the present study that was aimed to determine the effect of immediate loading of implants are placed in the fresh socket on the clinical success of the implant compared to delayed implant placement, significant results in term of success rate were obtained. In the past, Osseo integrated implants, which is the most important factor for the success of any implant-based prosthesis, was defined as success rate [42]. Thus, immediate implant placement is considered as a predictable treatment process and concept because many studies have indicated a high success rate for this technique [43–45].
Formerly, some studies reported a high success rate of the immediate loading of dental implant compared to delay procedure, but in some studies, which a very low success rate were reported. Thomé et al., reported the success rate of immediate implant placement as 99.6% [46]. Another retrospective study was conducted by Perelli et al, and showed that immediate loading of dental implant had a survival rate of 92.0% [47]. While Chaushu et al, who compared the immediate and non-immediate loading of dental implants, reported the survival rate for the immediate loading of dental implant was 82.4% compared to 100% for non-immediate procedure [48].
Given that the criteria for implant success have changed in recent decades, implant treatment has shifted from a bone-driven protocol to a restorative-driven protocol [49]. The results of this systematic review on immediate loading of dental implant showed not only less bone resorption but also an increase in marginal bone surface area may happen in the first year of implant. Therefore, at least it can be stated that immediate loading of dental implant, as much as the standard method of implant placement in the ridge, is effective in preserving bone in the short term [50].
Another important issue is the preservation of dental papillae. The main key in this case is the amount and level of bone in the proximal of the adjacent tooth [51]. The results of previous studies showed that immediate loading of dental implants could not have significant results in preventing papillary defect [52–55]. This result can be interpreted as that papillary preservation depends on the presence of interdental bone rather than on the surgical procedure and prosthetic protocol. In these studies, there was no significant difference in papillary height after 1.5 years of follow-up between immediate and delay loading of dental implants.
In the past, it was believed that placing the implant in the socket of a fresh socket would prevent bone remodeling and preserve the shape of the ridge [56]. But later on animal as well as human studies have ruled this out [57–60]. These studies have shown that regardless of the method of implant placement, remodeling will occur after tooth extraction and will lead to transverse and vertical bone resorption. On the other hand, bone resorption on the buccal side is much more significant than on the lingual side. This can be explained by the fact that the buccal bone crest is mainly composed of bundle bone, which loses its function and resorbs by extracting the tooth.
Another issue with the immediate loading of dental implants is the use of implants with a surface treatment that can have a higher rates r than bone-to-implant contact (BIC). On the other hand, the use of tapered implants in immediate implantation is more successful than the cylindrical type in achieving primary stability. However, in terms of the placement of the torques, no general agreement has been reached on their minimum amount in these studies [61, 62]. In general, by examining these studies, can say that immediate loading of dental implants can be problematic due to the presence of infection at the implant site, and the treatment protocol needs further and more detailed investigation in these cases. Besides, achieving primary stability in immediate loading of dental implant is the most important success factor. Immediate loading procedure also should not be done, especially in cases where the buccal bone defect has reached the crest area. Because in these cases it is necessary to use a bone graft with a membrane on the surface of the ridge and the prosthesis can no longer be placed on the surface of the implant. Another concern is the placement of the prosthesis in the occlusion. It is recommended that in an immediate implant, all the effort should be made to keep the temporary prosthesis out of the occlusion in all movements [63].
Bassir SH et al., 2019 shown that early implant placement protocol (risk difference = -0.018; 95% confidence interval [CI] = -0.06, 0.025; P = 0.416) like immediate placement protocols (risk difference = -0.008; 95% CI = -0.044, 0.028; P = 0.670) [64]. However, our study shows that immediate implantation, is a successful treatment process.
Review studies comparing the success of immediate and delayed implants have emphasized that in the short term there is no difference between the two implantation methods; but in terms of aesthetics and patient satisfaction and maintaining alveolar height, immediate implantation was better than delayed implantation. On the other hand, studies related to immediate implants, especially if followed by immediate loading had more failure rate [65]. These results are consistent with the information obtained from this study, with the difference that the mentioned studies considered immediate implant and immediate loading more successful in the anterior of the mandible, but in the studies included in this meta-analysis, this method was also evaluated as successful in the posterior the mandible and maxilla.
Different views were previously expressed on placement of implants after tooth extraction, which means that immediate implantation is a more complex treatment and delayed implants allow for better primary stability and better prosthesis placement. However, around 30% of immediate implants cases are aesthetically pleasing to patients, and survival rate of immediate implants are high and comparable to those in a recovered ridge [66, 67]. Also, another study that immediate implants do not prevent horizontal and vertical resorption after tooth extraction. On the other hand, bone width reconstruction after immediate implant placement prevents transverse bone resorption, however, vertical resorption of the buccal bone will continue. Interestingly, these studies provided strong evidence that bone regeneration, even in cases of immediate implants is more successful than delayed implants [68].
In a systematic review study [69], although a large number of articles reported a limited amount of bone loss or even an increase in its level in immediate implantation, these results should be interpreted with caution. Because few of these studies have been reviewed radiographically. However, in this study, only studies that expressed the exact amount of bone loss or increase based on radiography in millimeters were included in this meta-analysis.
In fresh socket, the gap between the implant surface and the bone wall is an important issue in the healing process. As the width of this cavity increases, the amount of BIC decreases and the most coronal part of the BIC migrates towards the apical part [70]. However, the authors state that implants with immediate loading will have a higher BIC than the delayed method, and less bone resorption will occur in these cases. In our study, it was also found that the rate of analysis was lower in the immediate implant group. However, in most of these studies, including this study, the difference between the two groups was not statistically significant. In general, randomized clinical trial studies with more samples are recommended so that long-term evaluation of results both in terms of success and bone resorption is possible .and meta-analysis can be performed with more robust studies.