RESUMEN
This research was carried out on twenty patients of upper completely edentulous arch against mandibular bilateral distal extension ridges to study the effect of different torqueing releasing clasps assemblies of mesially places occlusal rest on alveolar bone height change of the abutment tooth. According to the type of the clasp assembly design used in this study the patients were classified into four groups. Where the mandibular distal extension removable partial denture frame work retained with RPI, RPL, RPA and, modified clasp assemblies design were constructed for group I, II, III and, IV respectively. After making an altered cast impression with selective pressure impression technique, jaw relation was registered and the dentures were processed with heat cure acrylic resin. Pre-apical x ray film of the abutment teeth was performed immediately, 6 months and 12 months of denture insertion. The results of this study revealed at all studied groups exhibited significant abutment alveolar bone resorption, along the follow up periods, after insertion of mandibular distal extension RPS. After six months and 12 months follow up, abutment alveolar bone height change for mandibular distal extension RPD with RPI and modified clasp was significantly less than that of RPA clasp, on other hand comparing RPI, RPL and modified mandibular distal extension RPD wearer together was found insignificant in the abutment alveolar bone resorption the former and the latter exhibit an proximally equal amount of resorption. In conclusion, Modified and RPI clasps may be the clasp of choice because they exhibit less abutment alveolar bone resorption. RPL clasp is a substitute for the RPI clasp in distal extension cases