A patient reports significant pain each time the removable partial denture is inserted and removed. Which clasp adjustment is MOST appropriate?

Correct answer: D. Reduce the thickness of the retentive clasp arm terminal

• A. Adding retention compounds the problem when the existing retention is already excessive.
• B. Bending the clasp further into the undercut INCREASES the retentive force and would make the pain considerably worse.
• C. Shortening the arm makes it STIFFER and less flexible — the opposite of what is needed. Longer arms are more flexible.
• D. CORRECT. Pain on insertion and removal indicates that the retentive arm is engaging an EXCESSIVE undercut and applying too much force to the abutment as it flexes past the height of contour. Reducing the THICKNESS of the terminal third increases the arm's FLEXIBILITY, so it deflects more readily during the path of insertion and delivers less force to the tooth. Clasp flexibility varies with the cube of thickness, so modest thinning produces a large gain in flexibility.

Note: Clasp flexibility increases with LENGTH and decreases with THICKNESS and TAPER quality. If pain persists after adjustment, re-survey the cast — the arm may be engaging an undercut deeper than the alloy was designed for (cast chromium-cobalt tolerates roughly 0.25 mm; wrought wire tolerates more).