Abstract: BACKGROUND: Preliminary studies have shown that micro-grooved patterns of porous hydroxyapatite have good osteoinductivity, biocompatibility, and osteoconductivity, which provides a new idea for clinical repair of jaw defects and expansion of implantation.
OBJECTIVE: To observe the osseointegration of the micro-grooved patterns of porous hydroxyapatite with the dental implant after repairing large-area defect of the canine mandible.
METHODS: Micro-grooved patterns of porous hydroxyapatite were made. Eight beagle dogs were randomly divided into experimental group and control group (n=4 per group). Bilateral mandibular premolars of the dogs were extracted. Three months later, two cylindrical bone defects of 8 mm×10 mm were fabricated. The experimental group was implanted with micro-grooved patterns of porous hydroxyapatite and the control group was implanted with autologous bone. Three months later, a 4 mm × 10 mm Dentium implant was implanted in the bone defect repair area. Samples were taken at 4 and 12 weeks after implantation. Cone beam CT examination, Micro-CT scan, histological examination, and implant resonance frequency analysis were performed. 
RESULTS AND CONCLUSION: (1) Cone beam CT showed that there were some low-density shadows at the implant-osseointegration interface between the experimental group and the control group 4 weeks after the operation. At 12 weeks after the operation, the area of the implant-osseointegration surface increased in the experimental group and the control group. The implant was closely combined with the implant material, and there was no obvious shadow. (2) Micro-CT data analysis showed that the amount of bone covered on the implant surface in the experimental group was less than that in the control group 4 weeks after operation (P < 0.05). There was no significant difference in the amount of bone covered on the implant surface between the two groups at 12 weeks (P > 0.05). (3) Histological morphology: Hematoxylin-eosin, Masson and methylene blue-acid fuchsin staining showed that new bone formation was seen in both groups at 4 weeks. The bone contact rate in the experimental group was less than that in the control group (P < 0.05). At 12 weeks, the amount of bone around the implants in the two groups increased significantly. There was no significant difference in bone contact rate between the two groups (P > 0.05). (4) The resonance frequency analysis of the implants showed that the implant stability quotient of the experimental group was lower than that of the control group at 4 and 12 weeks after implantation (P < 0.05), but the implants of the two groups were stable in each period. (5) It is concluded that micro-grooved patterns of porous hydroxyapatite can repair large-area defects of canine jaws and induce the new bone formation, showing perfect osseointegration with implants. 

Key words: hydroxyapatite, implant, bone defect, osseointegration, scaffold, mandible