الفهرس 
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Abstract
The aim of this study was to evaluate the stress distribution in atrophied mandibular ridges by using either implant supported over denture with four mini implants or with two conventional implants through a finite element analysis method.
Three dimensional finite element analysis was used to compare the stresses in mandibular full-arch implant-supported over dentures loaded by simulated biting force. A finite element model derived from an edentulous human mandible with resorbed ridge was constructed. The model was duplicated into two identical models which were restored with implant supported mandibular over dentures supported by: Model A; two intra-foraminal standard diameter implants and model B; with four mini implants. A 450-N load for each side was applied on maximum intercuspation areas on all mandibular arch teeth.
A 450-N load for each side was applied on maximum intercuspation areas on all mandibular arch teeth according to balanced occlusion concept.
Considering stresses in alveolar bone, implants, and overdenture, the observed results in the present study suggest that overdentures supported by two conventional implants are the more favorable treatment option and provide a good alternative with reduction in the resulted stresses around peri-implants bone which suggest higher rates of implant failure as stated by Tomasi et al. 2014 in comparison with previous studies ( Elsayad et al. 2011)
Model B of mini implants showed the highest amount of stresses on the peri-implant bone. However model A experiencing conventional implants showed an approximately 27% stress reduction. The stresses on the implants bodies showed slight increase in model A by 1.07%
Due to fatigue loading, small cracks begin to form. The rate at which these cracks propagate has a direct influence on the fatigue life of the material.