Prosthodontics & Occlusion · single question
Which Kennedy RPD class REQUIRES indirect retainers?
Show answer and explanation
Correct answer: A. Class I (bilateral distal extension)
- A. Correct. Kennedy Class I (bilateral distal extension — free ends on both sides) and Class II (unilateral distal extension) are EXTENSION-BASE prostheses. They rotate around a fulcrum line when loaded, causing the distal extension base to move down and the anterior portion to lift up. INDIRECT RETAINERS are placed anterior to the fulcrum line to resist this rotation and prevent displacement of the anterior part of the denture.
- B. Incorrect. Class IV (single anterior space crossing the midline) is also bounded and tooth-supported — no indirect retainers needed.
- C. Incorrect. A Class II modification adds a bounded space — the modification itself doesn't require indirect retainers unless the primary classification is an extension base.
- D. Incorrect. Class III (bounded saddle — teeth on both sides of the space) is a tooth-supported prosthesis and does NOT require indirect retainers because there is no rotation around a fulcrum line from extension bases.
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