Purpose: This study aimed to investigate whether axial or radial functionally graded root analog implants can optimize the stress and strain distribution near the implant-bone interface in alveolar bone models under static loads using finite element analysis (FEA).

Materials and methods: The 3D profile of the root analog implant was captured from a natural tooth in CBCT data. The implant was separated into different layers (3, 5, and 10 layers) to vary the Young modulus axially or radially. The variation in Young modulus was designed to be linear, exponential, or parabolic. Different occlusal loads were applied. The von Mises stress and strain were used to evaluate the system risk of failure.

Results: The difference in the numbers of layers had no significant effect on the alveolar bone. In the radial functionally graded implant models, the maximum von Mises stress of the alveolar bone decreased as the outer layer's elastic modulus increased; however, in the vertical functionally graded implants, this stress varied little. The maximum von Mises stress of the cancellous bone changed only slightly, from 2 to 5 MPa in all models. The maximum strain of the alveolar bone varied from 0.001478 mm to 0.003999 mm. Those FEA results were in line with previous findings.

Conclusion: The functionally graded root analog implants show no significant biomechanical advantages over dense zirconia implants. Radial functionally graded root analog implants should optimize the peri-implant stresses and are biomechanically favorable for design.