| Hydroxyapatite(HA) is a kind of biomimetic materials and has being widely used in clinical application. It is mostly synthesized artificially. In Chien-shiung Wu Laboratory of Department of Biomedical Engineering in the Southeast University the natural HA has been epurated and they did the pilot study of preparing nano-grade-powder. The material had no cell toxicity in vitro. Based on the natural HA study the natural structure of bone was simulated and they prepared the natural hydroxyapatite/chitosan composite(NHC). In the first part of this study, NHC was implanted to the tibial defects of New Zealand rabbits. We observed the biocompatibility, osteogenesis and the changes of elements contained in the new bone metabolizability. We discussed the process of osteoconduction by NHC for providing a new treatment in the defect of jawbone. In the second part of this study, we produced the defect models around implants in the tibias of New Zealand rabbits. We repaired the defects with NHC and simultaneously titanium implants were placed into the bone defects. We analyzed the results of histological section, scanning electric microscope(SEM) and energy dispersive X-ray spectrum(EDX), and discussed the possibility of NHC repair and simultaneously dental implant surgery for providing theory basis for clinical application.Part I: The experimental research on the biocompatibility and osteogenesis of NHC in vivoMaterials and methods: we prepared the self-harding NHC. 18 white rabbits were each operated on left tibias to create two square bone defects. One of the defects was filled with NHC(experimental group), the other was not filled as a blank control (control group). 3 of theanimals were respectively killed at the end of 2 weeks, 4 weeks, 8 weeks, 12 weeks, 16weeks and 24 weeks. The specimens were made for anatomy observation, histological section, scanning electric microscope observation and energy disperse analysis of element Ca, P and S.Results: A mild inflammatory infiltrate was found at postoperative 2 weeks. New bone could be observed at postoperative 4, 8 and 12 weeks. The new bone became gradually mature through histological and SEM observation. The new bone was the same as the recipient bone and bony connection was shown at 16th week following the operation. The obvious absorption could not be seen in the central body of NHC at the 24th week following the operation. The thin new cancellous bone could be observed in the blank control group in all period. The results of EDX showed that the contents of element Ca and P increased obviously through 4, 8, 12 and 16 weeks(p<0.01), while the contents of element S decreased obviously(p<0.01) in the experimental group. Conclusions: NHC has good biocompatibility and osteoconduction. It can be used as repair material for bone defect.Part II: The experimental study on repairing the bone defects around implant with NBCMaterials and methods: We preformed 72 screw titanium implants with 2.0mm in diameter and 8.0mm in length. We used 12 New Zealand rabbits. Three holes were made in bilateral tibias of each animal. The diameter of the hole was 4.5mm in group A. NHC and implant were implanted to the bone holes. The diameter of the hole was 2.0mm in group B. Only implants were implanted to the bone holes. The diameter of the hole was 4.5mm in group C. Only implants were implanted to the bone holes. No filling was placed to the holes of group C. After 4, 8, 12 and 16 weeks, 3 rabbits were respectively sacrificed to make the specimens for Van Gieson stained section, SEM observation and EDX. The contents of element Ca, P and S of new bone in bone-implant...
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