Asian Journal of Dental Sciences

Implant supported prothesis are used in rehabilitation of cases with sever resorption of alveolar bone. However, the limitations due to the close proximity between critical anatomical structures (as maxillary sinus, inferior alveolar nerve)  and crest of the ridge sometimes lead to difficulties in implant placement. All on four technique was developed by placing four implants in the anterior maxilla or mandible, the two most distal implants was angulated to overcome bony deficiencies or anatomical structures and maximizing the available bone used without grafting. Biomechanical studies showed that the implants excess loading is the significant factor cause bone resorption. The goal of the Study was to evaluate the stress distribution of fixed implant-supported prostheses using “all-on-four” concept for the treatment of mandibular completely edentulous ridge “in vitro study”.

Materials and Methods: The finite element model components as the overdenture, mucosa, implants, angled base, abutment, cortical and cancellous bones were created in "Autodesk Inventor. The model was subjected to Six loading conditions of 100N, 50N vertically and oblique (antroposterior) at central incisors respectively. In addition to 200N and 100N unilaterally vertically and oblique (buccolingual) at molar region respectively, 200N and 100N bilaterally vertically and oblique (antroposterior) at molar regions respectively were investigated.

Results: All values of deformations and stresses appeared on the all model components were within physiological limits under all cases of load application.

Conclusion: tilted implants at molar area did not affect the system behavior (did not show beak of stresses or deformation).