[Effect of parathyroid hormone (1-34) and coralline hydroxyapatite on bone regeneration of peri-implant bone defects].

Objective To evaluate the effect of parathyroid hormone(1-34) [PTH(1-34)] and coralline hydroxyapatite(CHA) on bone regeneration of peri-implant bone defects. Methods Two implant sites were prepared on both sides of tibia in 8 mongrel dogs. The bone defect was created along one bone wall of each implant site. Implants were implanted into the implant sites, then CHA was grafted into the bone defects. After surgery, the animals were randomly divided into two groups. PTH(1-34) (40 µg/kg) was used for subcutaneous injection to the experimental group for three consecutive days, meanwhile the same amount of saline was given to the control group. Half of the animals of each group were sacrificed after 4 weeks and 8 weeks respectively. Specimens were subjected to implant pull-out strength tests, X-ray picture and histological observation. Results The bone density of bone defects in the experimental group were higher than that in the control group. No low-density images was observed between the implants and bone at 4 weeks and 8 weeks. The maximum pull-out force value of the experimental group(199.8 N,411.5 N) was higher at 4 weeks and 8 weeks than that of the control group(100.1 N,184.5 N) (P<0.05). The pull-out force value of the experimental group at 4 weeks and the pull-out force value of the control group at 8 weeks were similar. The new bone trabecular around CHA of experimental group was thicker at 4 weeks. Implant surface contacted to the new bone directly without fiber. CHA granules of the experimental group at 8 weeks were fewer than that of the control group. New bone tissue of the experimental group was denser. The contact area between implant surface and new bone was wider in experimental group than in the control group. Conclusions PTH(1-34) and CHA can promote bone regeneration of peri-implant bone defects, shorten the implants and bone healing cycle and improve the implants osseointegration. Key words: Dental Implantation; Hydroxyapatites; Parathyroid hormone-related protein