**1. Introduction**

Dental implant service is a life-changing treatment modality for many patients. Giving our patients a fixed restoration is a very rewarding procedure, especially if the patients have difficulties: gage reflex, bulky prostheses, lack in retention, stability, or support. Unfortunately, this is not applicable for all patients, especially patients who cannot afford multiple implants or bone grafting. By considering the strategic implants under the existing removable partial denture (RPD), we make implant treatment simple and affordable for more patients.

The removable partial denture (RPD) is the dental prostheses that the patient, who suffers the absence of some but not all the natural teeth, can readily insert and remove from his/her mouth. The prostheses restore the missing teeth as well as the gingiva and the missing bone if needed. Removable partial dentures (RPDs) are indicated for patients with a long edentulous span, too long for a fixed prosthesis. The RPD is indicated for a patient with no posterior abutment to support a fixed prosthesis, and the cantilever bridge is contraindicated. Also, it is preferred if excessive alveolar bone loss is encountered, especially in the esthetic zone. Those patients who are not indicated for bone grafting or unable to afford the costly treatment are good candidates for the removable denture (RD). The acrylic flang is a good approach to compensate for the bone and soft tissue deficiency within a short fabrication time and a less aggressive approach. Moreover, this treatment option allows the patient to remove his prostheses for easier intraoral access, subsequently, better oral hygiene. The RD enables the dentist to repair or adjust the prostheses easily.

On the other hand, RD is less secure with limited retention and stability than fixed prostheses. RD metal clasp may compromise the final esthetic result. It may act as a gum stripper and accelerate alveolar bone resorption. These drawbacks in the RD can be managed by upgrading the RD using strategic implants, which are "the implants that change the prosthetic support type to a more favorable configuration" [1].

In this chapter the folllowing points is going to be discussed:

	- Kennedy classification system
	- Steffel classification and modified Steffel classification
	- Implant-Corrected Kennedy (ICK) Classification System for Partially Edentulous Arches
	- Strategic mini dental implants (MDI) and standard dental implant (SDI) under existing RPD, how many implant?
	- The abutment prosthetic value
