Guiding planes in clasp reciprocation and retention.
Answers to two questions were sought: Is there a proper length for a guide plane and does the relationship of the guide plane to the undercut enhance retention? The cylindrical sleeve makes it possible to measure suprabulge contours in relationship to undercuts, thus establishing the "action distance" of the retentive arm. The reciprocating distance traveled by the reciprocal part of the clasp must be equal to the action distance: action distance = reciprocation distance = length of guide plane. Three sets of ivorine teeth were used with cast clasps with a connector and with a single clasp to test this concept of intrinsic retention--"intrinsic retention" being a guide plane opposed by an undercut at 180 degrees.
D000044:Dental Abutments; D003737:Dental Cavity Preparation / Q000379:methods*; D003781:Denture Retention; D003832:Denture, Partial, Removable; D006801:Humans; D014070:Tooth / Q000033:anatomy & histology