Stereophotogrammetric analysis of abutment tooth movement in distal-extension removable partial dentures with intracoronal attachments and clasps.

This study applied the three-dimensional measurement technique of stereophotogrammetry to measure abutment tooth movement under occlusal loading as a function of intracoronal attachment and clasp design. Six distal-extension removable partial denture designs were studied: (1) RPI-mesial occlusal rest, proximal plate, buccal I-bar; (2) cast circumferential clasp; (3) P.D. locking semiprecision attachment; (4) Thompson dowel nonlocking semiprecision attachment; (5) McCollum precision attachment; and (6) Stern G/L precision attachment. The movement in microns was determined by computer analysis. The Thompson dowel semiprecision attachment generated the most abutment movement in a gingival direction. The clasp-retained designs generally had less total movement than the attachment designs. Clasps and attachments for the abutment teeth adjacent to the distal-extension bases generally moved more than the abutment teeth.