The aim of this study is to compare the stress distribution of three different types of immediate loading implant-supported prosthesis with the conventional protocol of two surgical stages by using a Non-linear Three-Dimensional Finite Element Analysis. A total of four mathematical models representing an edentulous mandible with a full-arch prosthesis supported by four external hexagon implants (3.75 mm x 11.5 mm) with a 10-mm distal cantilever will be fabricated. In group A (control) - implants will be rigidly splinted by means a metallic superstructure and will be submitted to the conventional loading protocol of two surgical stages; in group B - implants will not be rigidly splinted (splinted by means acrylic resin), and will be submitted to immediate loading protocol; in group C - implants will be rigidly splinted by means a metallic superstructure and will be submitted to immediate loading protocol; in group D - implants will not be rigidly splinted (splinted by means acrylic resin), and a pre-manufactured distal bar will be inserted in the cantilever area, and will be submitted to immediate loading protocol. The mandible will be constructed by using a software (Simpleware) through computed tomography images of an edentulous mandible. Implants and prosthetic components will be fabricated by means a CAD software (SolidWorks). In order to simulate the immediate loading of implants (groups B, C and D) non-linear and frictional contact elements (0.3) will be inserted at the bone/implant interface. Models will be imported to the finite element analysis software (Abaqus) and a 100-N oblique (30 degrees) unilateral posterior load will be applied. Models will be fixed by vector forces on the insertion of masticatory muscles regions. The maximum, minimum principal stresses, von Mises stress and displacements on the -x, -y and -z axes will be determined. A descriptive statistical analysis will be performed.
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