A comparison of two types of four implant-retained overdenture attachments on the stresses introduced to the mandibular posterior residual ridge: 3D Finite Element Analysis.

The biomechanics of implant-retained overdentures can lead to different resorption patterns in the posterior regions of each arch. Two of the most commonly used attachment systems for these type of prostheses are Bar/clip and Ball/rider. The aim of the present study was to compare two types of implant-retained overdenture attachments on the stresses introduced to the mandibular posterior ridge by means of 3D Finite Element Method. This experimental study performed with Ansys software. The basic model was generated from data provided by a CT-scan of edentulous patient. Four root form implants were placed in interforaminal region of the mandible. Models were used in order to simulate two situations: In group A, model represented an edentulous mandible supporting an overdenture retained by Four-splinted implants connected with Bar/clip system while in group B, model simulated an edentulous mandible supporting an overdenture retained by Four solitary implants with Ball attachments. The occlusal load of maxillary complete denture was introduced in two directions for each group: vertical load as in centric occlusion,and oblique load as in working lateral excursion. The amount of stress introduced by overdenture using Bar attachment was higher in centric occlusion whereas ball attachment introduced more force in working lateral excursion. If the only determining factor for choosing the attachment system was the amount of stress introduced to the mandibular posterior ridge, then the Ball/rider system would be the attachment of choice.