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Mesial Rest Design — ORE Part 1 MCQ

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HardProsthodonticsMesial Rest DesignORE Part 1

A Kennedy Class II distal-extension removable partial denture has a free-end saddle supported by the residual ridge and a terminal premolar abutment with a distal occlusal rest. During mastication, the patient experiences soreness beneath the loaded saddle. Which alteration to the rest position is most likely to reduce the unfavourable loading responsible for this problem?

Educational content. Not a substitute for clinical judgement or local policy.

Reveal the answer and explanation

Correct answer: D — Move the occlusal rest from the distal to the mesial surface

Explanation lettering: D = shown as A · E = shown as C · A = shown as D · C = shown as E

The correct answer is **A**. A distal-extension RPD is tooth–tissue supported: the mucosa beneath the saddle displaces more than the periodontal ligament supporting the abutment. Loading of the saddle therefore causes rotation and transmits potentially harmful forces to the terminal abutment and supporting tissues. In an in-vivo comparison, a distal rest produced the most posteriorly directed abutment force, whereas a mesial rest produced the most anterior direction. Moving the rest mesially is therefore the relevant biomechanical modification. Enlarging a distal rest (B) retains the unfavourable rest position. Removing it (C) sacrifices essential support. An additional clasp (D) mainly affects retention, not the rest-related force pattern. More acrylic (E) may alter base rigidity but does not correct the underlying fulcrum and loading arrangement.

Reference: Kawata T, Kawaguchi T, Yoda N, et al. Effects of a removable partial denture and its rest location on the forces exerted on an abutment tooth in vivo. International Journal of Prosthodontics. 2008. https://pubmed.ncbi.nlm.nih.gov/18350947/