الفهرس 
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Abstract
Purpose: The aim of this study was to analyze the stress distribution and the resultant strain within complete telescopic overdenture made of a newly introduced thermoplastic (acetal resin) denture base material using a 3-D finite element analysis (FEA). Materials & Methods: Two heat-cured resins were used in this study namely; conventional heat-cured acrylic resin (methyl methacrylate) and acetal resin (polyoxymethylene) and a cobalt-chromium alloy. Finite element analysis (FEA) method has been used in the present study to analyze the stress distribution patterns and displacement in complete mandibular telescopic over denture made from either conventional heat-cured acrylic resin with acetal resin framework or conventional heat-cured acrylic resin with Co-Cr alloy framework. Two types of supports (bone and/or copper models) were used during FEA and the FEA has been performed by two techniques according to the type of load application. However the maximum forces of (150 N) were applied to the central fossae of the first molars. Additionally, a total of 10 over dentures were prepared for (mechanical testing) fracture resistance testing. The over dentures were divided into 2 groups according to the framework material. Five mandibular telescopic over dentures were fabricated from conventional heat-cured acrylic resin and Co-Cr alloy framework (control group). Additional 5 telescopic mandibular over dentures were fabricated from conventional heat-cured acrylic resin and acetal resin.Each telescopic complete over dentures were subjected to fracture resistance test using a Universal Testing Machine. The fracture load was recorded. The obtained data were statistically analyzed using One-way ANOVA. Results: The FEA results according to the first technique showed that the maximum Von mises stresses developed in telescopic over denture with Co-Cr alloy framework was higher (1.196MPa) than those developed in the over denture with acetal resin framework (0.099MPa). According to the second technique relatively lower Von mises stress value were generated within the over denture with the acetal frameworks (110 MPa) than those generated within the over denture with the Co-Cr framework (120MPa) Furthermore, better stress distribution in the over denture with the Co-Cr alloy framework was observed .Conclusions The use of Finite element analysis with occlusal pressure technique is availed and corresponds with the mechanical testing of telescopic overdentures.