| Objective: The lack of bone mass is a common problem in implantsurgery which will pose a threat to implanting success rate.Many researchersinvestigate the use of various bone graft to repair peri-implant bone defects.Asa common bone graft material in clinical,artificial bone(hydroxyapatitebioceramic) has good bone conduction and biocompatibility.But hydroxyapatitegranules often shift with external factors, and have a lower degradation rate invivo.Therefore, only using of artificial bone to repair peri-implant bone defectwill increase the time of bone regeneration and osseointegration,and extend thepost-repair load time.As an osteogenic drug, parathyroid hormone (PTH) canpromote bone regeneration and increase bone density.It is the only osteogenicdrug approved by FDA.This experiment was designed to study the effects ofPTH (1-34) and artificial bone on bone regeneration and dental implantsosseointegration of peri-implant bone defects by biomechanics test andhistomorphometric observations,hoping it will provide references for the futureresearch and clinical application.Methods:Two implant sites were prepared on both sides of proximal endof tibia in8mongrel doges.The bone defect (3mm×3mm×4mm) was createdalong one bone wall of each implant site.Implants were implanted in theimplant sites,and artificial bone was grafted into the bone defects.Aftersurgery,the animals were randomly divided into two groups.Per week forconsecutive three days,we used40μg/kg PTH(1-34) for subcutaneous injectionto the experimental groups,and took an equal amount of saline to instead at thenegative control groups.Half of the animals of each group were sacrificed after4weeks and8weeks respectively. Tetracycline was intramusculared to the animals for fluorescent label at one week before and one day before put todeath.We took the specimen blocks for X-ray,then selected them randomly.Halfof the specimen blocks were received pull-out strength tests by electronicuniversal testing machine,and the rest ones were made into hard tissuesections,which were prepared for the observation of fluorescent markersituation and histomorphology.Results:In general observation, the experimental groups’ artificial bonegranules without ossification on the surface of the bone defects were less thanthe ones in the control groups, and boundaries with the surrounding normalbone were not so clear than that in the control groups whether at week4orweek8. Imaging results showed that,at week4,no low density was showed inthe bone defects of the experimental group,compared to the negative controlgroup.Trabecular bone in the experimental group was larger and thicker,cortical bone showed a white high-density image,and no low-densitytransmission images were seen between bone-implant interface.At week8,theimage differences between the experimental group and the control group werebasically the same as at week4.At week4,the maximum pull-out force value(199.750N) of the experimental group was significantly higher than that in thecontrol group (100.050N),(P <0.05).At week8,the maximum pull-out forcevalue (411.500N) of the experimental group was significantly higher than thatin the control group (184.500N),(P <0.05).The maximum pull-out force valuebetween the experimental group at week4and the experimental group at week8was significant different(P <0.05).The maximum pull-out force valuebetween the control group at week4and the control group at week8wassignificant different(P <0.05).The pull-out force value of the experimentalgroup at week4and the pull-out force value of the control group at8weekwere similar.The green fluorescence band of the experimental group at week4was larger, brighter, and connecting to each other better than that of the control group.Compared with the control group,the fluorescence band of theexperimental group at week8is still wide, but the brightness of the two groupswas not as good as4weeks’.Artificial bone granules of the experimental groupat week4were smaller than that of the control group.The new bone trabeculararound artificial bone of experimental group was thicker than that of the controlgroup, and the canals were smaller.Implant surface contacted to new bonedirectly withotut fiber.Artificial bone granules of the experimental group atweek8were fewer than that of the control group.New bone tissue of theexperimental group was denser than that of the control group.The canals weresmaller than that at week4.The contact area between implant surface and newbone was wider than that of the control group.Conclusion: PTH(1-34) and artificial bone can promote bone regenerationin peri-implant bone defects, and accelerate the repairing of bone defects.A lotof the new bone tissue expand the contact area between implant surface andnew bone, which can improve the osseointegration of implants. |
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