Residual Ridge Stress and Mucosal Displacement under Two-Implant-Supported Mandibular Overdenture, Using Finite Element Analysis

Proper stress distribution in the edentulous ridge is necessary for implant-supported mandibular overdenture. For the purposes of the present study, the stress distribution was investigated under various types of forces using the finite element method (FEM). A digital model of the mandible with two implants (ITI with diameter and length of 4.1 and 12 mm, respectively) in canine areas and the overdenture supported by it were simulated using ABAQUS software. A vertical force was applied to the left first molar and gradually increased from 0 to 50 N. Finally, the resultant stress distribution was evaluated. Under small amounts of occlusal force, mucosa displacement and stress accumulation in the cortical bone of edentulous ridge, occurred on the non-working side and moved to the working side with a gradual increase in the force. Major stress accumulation was observed in the cortical bone around the implant. Moreover, it was observed in a minor range in the posterior ridge. The mucosa displacement occurred primarily in the posterior edentulous ridge, especially in the mylohyoid ridge. By using 3D FEM in the present study, it was observed that mucosa displacement is more likely to occur in the posterior areas, especially mylohyoid ridge and edentulous ridge crest in comparison to the areas around the implants. Therefore, this area should be carefully reliefand the forces should be directed towards the buccal shelf area as much as possible.