Implant-supported/retained mandibular overdentures have three crucial components: the implant fixtures (02 or more), the choice of attachment (bars, pins, or magnets), and the prosthesis. The Mc Gill consensus reported a minimum therapeutic objective: the two-implant mandibular overdenture (as opposed to a conventional prosthesis) should be considered as a first choice standard of care for the edentulous patient5. Mericske-Sterne also concluded that the retention, stability, and occlusal balance of implant-supported mandibular overdentures improved only slightly by increasing the number of implants.7 Implant survival rates did not vary with the number of implants and ranged from 93 % to 100%.8- 19 These results suggest that the number of implants is more important to support a prosthetic superstructure which can be in the form of a bar, pin or magnets for optimal load distribution. The results of this study showed that the interocclusal space and interforaminal distance determine the number of implants and the choice of superstructure for overdentures supported/retained by mandibular implants. Prosthetic complications in mandibular overdentures have remained a topic of interest in the literature. Berglundh in 2002, in his systematic review, concluded that the prosthetic complications reported in overdentures on mandibular implants were 4 to 10 times greater than in fixed implant-supported prostheses20. Looking at the above literature it becomes increasingly important to give further consideration in the planning phase of implant treatment. supported/retained mandibular prosthesis. It is necessary to respect the individual anatomical variations of the patients and the treatment plan regarding the number of implants and the choice of the superstructure must be basic... in the center of the paper... mm. For Class IIIa, a four-implant option with ball or locator attachments can be used when designing the prosthesis. Class IIIb where IFD ≤ 30 mm and IOS is between 6 and 8 mm. For Class IIIb, either option could be used with localizer-type attachments during prosthesis design. The decisive factor for the rehabilitation of edentulous patients with implant-supported mandibular overdenture is the interforaminal space, however the final selection is modified by IOS. Conclusion The classification system described here is intended to help clinicians effectively assess and communicate their patient's size relationship. This classification system would also facilitate decisions regarding pre-surgical tissue manipulation, design of final prostheses, choice of number of implants and attachment systems in the early stages of treatment planning..