A Research On Preparation And Properties Of Biodegradable Oral Guided Bone Tissue Regeneration Membrane

The jaw is an important part of the oral-maxillofacial system.It not only plays a bony supporting role,but also serves as the structural basis for chewing,swallowing and speech.Dental caries,periodontitis,tumor,trauma,osteomyelitis and congenital diseases can lead to jaw defect or loss,and the incidence of oral and maxillofacial diseases is the first.Guided bone regeneration（GBR）technology takes advantage of the different characteristics of bone and soft tissue growth to place a biomaterial GBR membrane between soft and hard tissues.On the one hand,the implanted membrane can act as a barrier to prevent fibroblasts from rapidly growing into the bone defect area and guards the osteogenic space;on the other hand,it can guide cell growth and promote tissue regeneration and repair on both sides of the membrane.Therefore,the selection and use of GBR membrane is the key to the success of this technology.Biodegradable GBR membrane is the direction of clinical development in the future.Biodegradable polycaprolactone（PCL）and polylactic acid（PLA）have been clinically approved as biomedical materials.However,the artificial polymer has some disadvantages,such as hydrolyzed acid,which may cause inflammatory reaction,and insufficient biological activity.According to the design idea of composite materials,a feasible strategy is to use pure Mg strips as the intermediate layer of the GBR membrane.On the one hand,it can provide better mechanical support for polymer materials.On the other hand,the Mg²⁺released by Mg during the degradation process has good biological activities such as promoting bone and promoting vascularization,and the OH^-generated by degradation can also can also neutralize the acid hydrolyzate produced by the degradation of the polymer,inhibit the inflammatory response,and regulate the degradation rate.On this basis,this study also incorporates nano-Mg O as a functional enhancement phase into the polymer,which can not only provide slow-release active factors,but also neutralize the acid product of the polymer,and its antibacterial properties can also avoid the application process of GBR membrane bacterial infection in.In view of the existing GBR membrane on both sides of the functional difference,insufficient mechanical properties,insufficient biological activity and other problems,in this paper,the solution casting method and the electrospinning method were used to prepare the Mg O/PCL casting membrane and the Mg O/PLA spinning membrane,respectively.On this basis,a Mg O/PCL-Mg-PLA three-layer structure membrane was prepared by adding magnesium strips.At the same time,for comparison,a Mg O/PCL-PLA double-layer structure membrane without magnesium strips was prepared as a comparison.In the experiment,by characterizing the physical and chemical properties of each membrane layer,the characteristics of the double-layer structure GBR membrane and the three-layer structure GBR membrane in PBS buffer were studied,and the antibacterial properties of the double-layer structure GBR membrane and the three-layer structure GBR membrane were explored by the addition of Mg O.The overall performance of each membrane layer is evaluated,and the specific conclusions are as follows:（1）The dense n Mg O/PCL（n=0,1 wt%,2 wt%,4 wt%）casting membrane was prepared by solution casting method.With the addition of nano-Mg O,the crystallinity and mechanical properties of the composite casting membrane have the same change,showing a trend of first increasing and then decreasing.The maximum crystallinity of 2 wt%Mg O/PCL casting membrane was 67.9%,and the tensile strength was 13.5MPA.n Mg O/PLA membranes with porous structure were prepared by electrostatic spinning method.With the increase of Mg O,the tensile strength of the spinning membrane was 4～5MPa,and the fracture elongation of the spinning membrane decreases gradually from 313.0%to 154.7%.（2）The tensile strength of GBR membrane is 7.7～8.9MPa.After 28d in vitro degradation,holes and cracks were formed on the surface of the spinning layer and the casting layer,and the mechanical properties remained good.With the increase of nano-Mg O content in the composite membrane,the degradation degree of the double-layer GBR membrane was improved.（3）The tensile strength of the three-layer GBR composite membrane is 34.5～39.1MPa,which is significantly higher than that of the bilayer GBR membrane.After 28d in vitro degradation,the mechanical properties of the GBR membrane maintained well,except that the tensile strength of 4 wt%Mg O/PCL-Mg-PLA was reduced to half of the original.With the increase of Mg O content,the hydrophilicity and hydrophobicity of the three-layer films changed significantly,which promoted the degradation of the whole film.Mg（OH）₂ and Mg₃（PO₄）₂ deposited on the surface of Mg strips inhibited the degradation of Mg strips.（4）the antibacterial rate of bilayer GBR membrane and three-layer GBR membrane against Escherichia coli or Staphylococcus aureus reached more than 95%,showing good and similar antibacterial effect.