Abstract
The purpose of this study was to investigate the effect of the modification of clasp assemblies under horizontal load. The simulated mandibular model with unilateral free end was fabricated for this study. The eleven types of removable partial dentures (RPDs) using different retainers respectively were constructed. These retainers were a cone-telescopic crown, Akers clasp, double Akers clasp, RPI clasp (Kratochvil type) and seven modified clasps made from the first three clasps to which an enlarged bracing arm, a positive rest with hook and a distal rest with a guide plate were added. Horizontal loads were applied, and the stress on abutment teeth and the displacement of denture base were measured.
The results were as follows:
1. Under horizontal loads, the partial denture retained by cone-telescopic crowns had the least displacement of denture base.
2. The RPDs with Akers clasps, double Akers clasps and RPI clasps generated large displacement of the denture base.
3. The stress characteristics on abutment teeth and displacement of denture base of the RPDs with modified clasps were similar to those of cone-telescopic crowns with enlarged lingual bracing arms, especially.
