RESUMO
BACKGROUND: The present study evaluated histologically and histometrically the efficacy of micro-, nano-, or mixed-composite of hydroxyapatite (HA) graft in treatment of surgically created defects around dental implants in mongrel dogs. METHODS: Immediate implant was used after extraction of the lower third premolar in mongrel male dogs. Critical-size defects were created in intact proximal alveolar bone to each implant. The defects were divided randomly into four groups of two animals based on biomaterials used for treatment: 1) received no treatment (negative control); 2) defects treated with nano-HA bone graft; 3) defects treated with micro-HA bone graft; and 4) defects treated with a mixed composite of micro-HA and nano-HA. Animals were sacrificed at 2 months and histologic and histometric evaluation was performed. RESULTS: The amount of new bone formed with nano-HA bone graft was highly more significant than that obtained by a micro- or mixed-composite of hydroxyapatite. Defects treated by mixed hydroxyapatite showed the greatest value in mean area percentage of collagen fibers using Masson trichrome stain. CONCLUSIONS: The present study demonstrated that nano-hydroxyapatite bone graft was better than micro-HA or mixed-HA bone graft in new bone formation in standardized surgically created defects around dental implants. However, longer period is necessary to determine the time taken for complete resorption of bone graft materials and their replacement with new bone.