Per the Lekholm and Zarb bone quality classification, which bone type generally presents the greatest challenge for achieving dental implant primary stability?

Type IV bone (very thin cortical bone with low-density trabecular bone, most commonly encountered in the posterior maxilla) presents the greatest challenge for achieving adequate implant primary stability, often requiring modified surgical protocols (e.g., under-preparation of the osteotomy, different implant designs, or staged loading approaches).