Experimental Study On Cranial Bone Defect Repair With Xenogenic And Autologous Dentin In Rabbits

Objective The repair of bone defect is still an important problem in clinical practice.Dentin as a new kind of bone defect repair material has attracted people's attention.Methods of treating dentin include boiling,demineralization,burning,liquid nitrogen freezing,etc.The treated dentin showed good biocompatility and promoted new bone formation.However,it is necessary to further study whether the xenogenic undemineralized dentin alone can achieve good biocompatibility and promote the formation of new bone.In this study,xenogenic dentin without demineralization was used as the graft material and compared with the autologous bone graft material to observe the osteogenesis effect of xenogenic dentin.Methods1.Animal group:24 healthy New Zealand white rabbits,male,weighing about 2.5Kg,and four bone defects were made in each rabbit's skull.Each rabbit's bone defect area was randomly divided into four groups,group A was human dentin group,group B was autologous dentin,group C was autologous bone group and group D was the blank control group;2.Preparation of dentin:Collected healthy premolars which extracted for orthodontic reasons and extracted rabbit central incisors.Cleaned teeth,removed the soft tissue on the surface and the pulp inside the pulp cavity and removed enamel and cementum.Grinded them into small block,socked in 0.2% chlorhexidine solution for10min;3.Animal experiments:After anesthesia,5cm long incision was made in the parietal using surgical blade,cut the skin and subcutaneous tissue,muscle layer andperiosteum,exposed the skull.Two 8mm diameter bone defects in each side of the skull were made with a annular drill.The removed skull bone was grinded into 2-3mm bone blocks.Prepared human dentin blocks,autologous dentin blocks,autologous bone which weight 0.3g respectively were put in the bone defect randomly and leave blank contrast,then covered Bio-Gide membrane.The wound was stratified and tightly sutured;4.Observation methods:Mental status and diet of rabbits were observed closely after the operation.Specimens were collected from 8 rabbits at 4 weeks,8 weeks and 12 weeks after the operation.Observed whether the bone defect was dense or not and whether there was fibrous encapsulation.Micro-CT was used to observe and calculate the bone volume fraction.The new bone formation and the number of inflammatory cells were observed histologically.SPSS22.0 software was used to process all data and one-way ANOVA was used.The difference was statistically significant when P<0.05.Results1.During the feeding period,all rabbit were fearless of cold and fever.There was no redness,swelling or bleeding in the surgical wound.At 4 weeks after the operation,the surface of the bone defect was covered fibers.At 8 weeks after surgery,the boundary between bone defect and surrounding bone tissue was not obvious,and the material became dense in xenogenic dentin group,autologous dentin group and autogenous bone group.At 12 weeks after the operation,the boundary between the bone defect area and the surrounding bone tissue was more blurred and the material was dense in above three groups,the experiment area of the blank group was less dense;2.Micro-CT showed that the amount of bone formation of xenogenic dentin group and autologous dentin group was similar to that of autogenous bone group,the difference was not statistically significant(P>0.05),and the difference between those three groups and the blank group was statistically significant(P<0.05);3.At 4 weeks after surgery,dentin groups had a small amount of new bone formation,osteoblast and fibrous connective tissue,new bone tissue surrounded thegrafted dentin and a small amount of inflammatory cells were visible,dentin blocks were located in the bone defect area,dentin was absorbed,with the time increase,dentin was absorbed more,inflammatory cells reduced.There were no statistically significant differences among groups of xenogenic dentin,autologous dentin and autogenous bone(P>0.05).Conclusion1.Both xenogenic dentin and autologous dentin can promote the formation of new bone and the amount of new bone;2.Xenogenic dentin,as a graft material,showed no obvious immune rejection,indicating that the low immunogenicity of dentin;3.Dentin is easy to obtain and has good biocompatibility,which can promote the formation of new bone and hopefully provide a new idea for the repair of bone defects.