Impact of short implants numbers and prosthesis design on stress in the posterior mandible: FE analysis

This study assessed the effect of the number of short implants on stress and strain distribution in bone in the posterior mandible using finite element analysis (FEA).

The study design utilized FEA, a computational technique. In FEA models, short implants (4 mm diameter and 6 mm length) were placed at the site of the mandibular first premolar to the second molar in four models: (I) two implants at the sites of teeth #4 and #7 with two pontics at the sites of teeth #5 and #6, (II) three implants at #4, #5, and #7 with one pontic at #6, (III) three implants at #4, #6, and #7 with one pontic at #5, and (IV) four implants at #4, #5, #6, and #7 with no pontic. A 100 N load was applied vertically and at a 30° angle to the occlusal surface of the crowns. Stress and strain distribution patterns in bone were evaluated using ANSYS Workbench.

The highest maximum von Mises and shear stress and strain values under vertical and off-axial loadings were observed in the model with two short implants at the sites of teeth #4 and #7 with two pontics at the sites of teeth #5 and #6. In general, the highest stress and strain values were recorded following the application of off-axial loads compared to vertical loads. In all models, the highest stress was noted in the cervical part of the implants, while the maximum strain occurred in the apical part of the implants.

Increasing the number of short implants significantly reduces stress and strain values in peri-implant bone.