When placing implants in the posterior mandible, it is crucial to engage all three layers of bone: the superior cortical bone, the medullary bone, and the inferior cortical bone. This provides maximum primary stability and enhances osseointegration by utilizing the dense cortical bone for mechanical retention while allowing vascularized medullary bone to support biological healing. Failure to engage both cortical plates can lead to reduced implant stability and increased risk of micromovement, jeopardizing implant success. Additionally, bicortical engagement helps in withstanding masticatory forces, which are typically higher in the posterior mandible.

Reference: Misch, Carl E., Contemporary Implant Dentistry, 3rd Edition.