الفهرس 
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Abstract
Objectives: The goal of this study to evaluate in-vitro, the stress transmitted to the abutment teeth and in-vivo, crestal alveolar bone height change of abutment teeth of distal extension removable partial denture retained with double arm stress releasing clasp of anterior placed principle occlusal rest. Materials and methods: In-vitro study was carried on partially edentulous mandibular acrylic resin model “replica” of bilateral distal extension ridge. Strain gauges were bond at buccal, lingual and distal surfaces of the abutment.In-vivo study was carried out on fifteen male patients of mandibular distal extension ridge posterior to first premolar against maxillary complete edentulous arch. The patients were divided in to three groups retained with reverse circlet clasp (group I), modified half-and-half clasp assembly (group II) and modified RPA stress releasing clasp (group III). The abutment alveolar bone height change was evaluated radiographically immediately after insertion, after first and second six months of denture insertion.
Results: For all groups, abutment alveolar bone resorption was significantly observed along the interval periods of study. group I (Reverse circlet clasp) showed significant increase in abutment alveolar bone resorption compared to group II and group III independently. Bilateral loading of the distal extension RPD revealed that, group I applied more stresses transmitted to the abutment compared to group II and group III independently.
Conclusion: Modified half-and-half clasp assembly and modified RPA stress releasing clasp assembly superior to reverse circlet clasp regard to abutment alveolar bone resorption of distal extension cases.Reverse circlet clasp not purely stress releasing by disengagement regarding double arm clasp utilizing in this study. from stress transmitted point of view (bilateral loading), modified half-and-half clasp assembly exhibit less stresses transmitted to the abutment compared to modified RPA stress releasing clasp assembly.