Extracranial and mandibular augmentation with hydroxyapatite-collagen in induced diabetic and nondiabetic rats

This study evaluated three hydroxyapatite (HA) preparations placed subperiosteally in rats given streptozotocin (70 mg/kg) to induce diabetes (ID) (n = 24) and in nondiabetic (ND) rats (n = 24) used as controls. Implants of 1) nonporous HA granules (HAG), 2) HA granules hand-mixed with bovine collagen (HACM), and 3) HA granules and purified fibrillar collagen in a preprocessed block (PFC-HA) were randomly placed in subperiosteal pockets created on the cranium and adjacent to the left/right mandibles of each rat. Six rats from each group were killed at 3, 6, 12, and 24 weeks postimplantation. Animals killed after 3 weeks showed sporadic bone proliferation and bone resorption, whereas those killed after 6, 12, and 24 weeks showed formation of new bone at the implant/bone interface. Contact of the implant with bone was a requirement for osteogenesis, but bone formed only into the basilar layers of the implants. The ID group showed the greatest inflammatory response as well as the greatest degree of osteogenesis at all intervals of time. The addition of collagen to HA appeared to reduce the inflammatory response. Specimens implanted with HACM showed the least inflammation of the three implanted materials in both ID and ND groups.