A patient is missing teeth #17, #18, #19, and #30, #31, #32. For a Kennedy Class I removable partial denture, where should the occlusal rest seats be placed on the abutment teeth?

For a Kennedy Class I bilateral free-end saddle (distal extension) removable partial denture with missing posterior mandibular teeth, the principle of mesial rest placement on the abutment teeth is employed. By placing rests on the MESIAL fossae of teeth #20 and #29 (the second premolars adjacent to the edentulous areas), the direction of force is directed toward the anterior teeth, reducing the tipping moment on the abutment teeth and distributing occlusal forces more favorably. Distal rests on these abutments would increase the rotational leverage on the distal extension base, which is unfavorable biomechanically. This is the RPD rest seat design principle for distal extension cases.