Which thread design for root form implants best resists shear forces?

The square thread design for root form implants is particularly effective at resisting shear forces due to its unique geometry. The square shape provides a larger surface area for contact with the surrounding bone, which enhances the load distribution during functional stresses. This design minimizes the risk of displacement or loosening due to shear stress, which can be a concern with other thread types.

The square threads facilitate a more stable grip within the bone by engaging in a more efficient manner, allowing for greater resistance against lateral forces that occur during mastication or other movements. Additionally, the right angles of the square threads help in transferring forces more effectively to the implant body, reducing the likelihood of micro-movement and subsequent osseointegration failure.

In contrast, while other thread designs like triangular, circular, or hexagonal may also provide some level of shear force resistance, they do not offer the same level of efficiency in load distribution and surface engagement as the square thread design. The triangular threads can lead to point loading, and circular threads may not provide as much resistance to lateral forces as square threads do. Hexagonal threads can offer some advantages, but they typically come with complications resulting from their geometry that may not make them as favorable as square threads for this specific purpose.