## 4 Discussion  
The present systematic review aimed to investigate the survival rate of immediate loaded MDIs to retain mandibular overdentures in dedentulous patients. Although MDIs were introduced around 15 years ago, however, there is a dearth of published studies regarding implant/prosthodonic literature [13]. Moreover, only four articles reported a follow-up duration of \(\geq\)3 years. Additionally, relatively low sample size was observed in the majority of the included studies. Furthermore, no study compared the MDIs with narrow diameter dental implants, while only four studies compared the MDIs with SDDIs for fixed prosthodonic therapy. In addition, no study described the application of immediate loaded MDIs to retain maxillary overdentures. Contrarily, a few reports on the application of MDIs for orthodontic therapy were observed [45; 46; 47]. This might be due to the short duration that MDIs are utilized in orthodontic treatment; this aids in designing the study. In the current review, NDDIs were not considered to be included in order to perform a more targeted search. This explicit differentiation between MDIs and NDDIs was made to resolve all possible ambiguities. The GOMI definition of MDIs and threshold of \(>\)3 mm implant diameter was applied [48]. As no previous consensus reports or clinical studies have differentiated between these two kinds of dental implants, we selected the GOMI definition of MDIs in combination with a threshold of \(>\)3 mm implant diameter. According to the authors of the present review, a dental implant having a diameter of \(\leq\)3 mm is best considered to be an MDI, which is considerably different from NDDI. This adoption of the GOMI definition and 3 mm implant diameter threshold is recommended for future studies on MDIs. The hypothesis has been accepted since this systematic review reported a high survival rate (97.3%) for immediate loaded MDIs for retaining mandibular overdentures, and this survival outcome was comparable to those using SDDIs to retain overdenture prosthesis [49; 50]. These outcomes suggest that MDIs for mandibular overdentures might become a feasible therapeutic technique, particularly for patients having limitations including financial constraints because SDDIs need a particular retention system for retaining prostheses (i.e., bar-clip, ERATM, O'ring), while MDIs are mostly single-body dental implants including the ball system. Furthermore, postoperative morbidity is decreased by using MDIs in patients who are unable to be subjected to extensive surgical procedures; in the majority of instances, the installation of MDIs is carried out without the utilization of surgical flaps [30; 51]. Generally, the overall survival rate of immediate loaded MDIs for retaining mandibular overdentures is favorable as reported by the outcomes of the present review. Of the included studies, four studies compared the utilization of MDIs with SDDIs. According to two reports conducted by [PERSON] et al. [37], lower survival rates were exhibited by MDIs in comparison with SDDIs, i.e., one SDDI failed (98%), while three MDIs failed (94%). Similarly, according to [PERSON] et al. [8], MDIs showed lower survival rates as compared to SDDIs, i.e., two MDIs failed (98%), while no SDDI failed (100%). In the present study, a higher survival rate (\(>\)96%) was observed by utilizing longer MDIs (10-18 mm) as compared to shorter MDIs (8-14 mm) (\(<\)95%). Similar outcomes were noticed in a study reported by [PERSON] et al. [52], according to which MDIs having a short length (7-10 mm) exhibited a higher failure rate as compared to longer MDIs (14 mm). Hence, the longevity of MDIs might be affected by their length, and longer MDIs should be chosen for better treatment outcomes. Of the 11 included articles, nine were prospective studies, while two were clinical trials.