Optical intensity changes under static load and their dependence on dental implant design around bone-mimicking...

Dental implants (DI) are among the most effective solutions for restoring masticatory function in patients with tooth loss. The success of these implants often depends on selecting appropriate design parameters, such as length and diameter, to ensure optimal outcomes. Understanding how these variables influence load transfer to the surrounding bone is essential for improving DI performance.

We aimed to evaluate the effects of implant diameter and length on static load distribution to surrounding bone-mimicking material (BMM) under identical optical and mechanical conditions, using an original and more accurate photoelastic testing method.

Epoxy resin was used to replicate the mechanical behavior of the bone under static load conditions. A total of 12 DI designs with varying lengths and diameters were tested, with three replicas each ( $n=36$ ). Polarized light was applied to the apex of each implant to detect optical intensity changes ( $\Delta I$ ) in the BMM under a 150-N static load and at rest.

A significant correlation was found between implant diameter and load distribution ( $p<0.05$ ). Wider implants showed more uniform load transfer, with 4.5-mm versus 5.5-mm-diameter implants showing 2.47 times less polarized light change, and 4.5-mm versus 6.9-mm implants showing 18.38 times less. By contrast, implant length had no statistically significant impact on load distribution ( $p>0.05$ ). The 6.9-mm diameter and longest implants transmitted the highest load to the BMM, whereas 11.5-mm length implants showed the lowest optical intensity changes ( $\Delta I$ ) under static load.

Implant diameter has a greater impact than length on stress distribution to surrounding structures. Emphasizing diameter selection may enhance implant longevity and clinical success.