الفهرس 
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Abstract
This in vitro study was carried out on ready-made epoxy resin models to compare the stresses induced by two different prosthetic designs for restoring mandibular unilateral free end saddle (class II Kennedy classification). The models were prepared to stimulate the oral cavity. Periodontal ligament of the artificial teeth was simulated by adding 0.3 mm Silicone material around the roots. Oral mucosa simulation was also simulated by adding a layer of 2 mm silicone material over the ridge area. On the epoxy resin models, two different prosthetic designs were constructed as follow: Model A: Lower metallic partial denture was made with RPI clasp as a direct retainer on the second premolar and double Aker clasp for cross arch stabilization on the 1st and 2nd molar the of dentulous side and lingual plate as a major connector. Model B: Lower metallic partial denture was made with extra-coronal attachment (OT) as a direct retainer on the second premolar which were splinted to the first premolar by crowns. Grooves and tunnels were made in the models to facilitate strain gauge measurements. Six strain gauges were installed, opposing to the buccal and lingual surface of the lower 2nd premolar, the ridge in the area of lower 7 molar and in the area of double Aker in the other side in model A. While four strain gauges were installed , opposing to the buccal and lingual surface of the lower 2nd premolar and the ridge in the area of lower 7 molar in model B. A digital loading device was used to apply ascending load at 70 N, 140 N and 200 N vertically and obliquely on the models. The strain was measured with digital strain meter and recorded. The result of this study had revealed that: - 1-Stresses recorded at buccal and lingual sides of the abutment tooth on vertical & oblique load in case of conventional RPD were higher than the OT attachment. 2-Stresses recorded at buccal and lingual sides of the ridge in the area of lower 7 molars on vertical & oblique load in case of conventional RPD were higher than the OT attachment. 3-Stressses recorded at buccal and lingual of the abutment tooth on vertical & oblique load were higher than stresses recorded at buccal and lingual of the ridge in the area of lower 7 molars in the two models. 4-Total stresses recorded at the buccal and lingual of the abutment tooth, the ridge in the area of lower 7 molar and double Aker in the other side in model A were higher than stresses recorded at the buccal and lingual of the abutment tooth and the ridge in the area of lower 7 molars in model B vertically and obliquely.