The Preparation Of Porous Chitosan Membranes And The Preliminary Study On Its Application As Biological Factor Vehicles In Pulp Capping

Calcium hydrate has been used as a direct pulp capping agent for several decades.Many researches showed that this agent was effective in clinics.However,in the process of pulp tissue healing,some further damages,such as coagulation necrosis,to the tissue surface by the agent were frequently observed.To establish a biological therapeutic method of pulp caping,the development and reparation after injury of the dental pulp have been investingated profoundly.It has been found that some biological factors such as TGF- 1 and IGF - I/II are deeply involved in the processes.However,application of exogenous growth factors requires consideration of the delivery vehicle for the molecules,the dose response effects,the half-life of the molecules,the possible immunological problems and so on.In this study,chitosan was prepared into membranes with suitable thickenss and porosity,and the feasibility of applying it as biological factors vehicles.was investingated.Methods:(l)By the method of cryogenic induced phase separation(CIPS) two kinds of porous chitosan membranes were prepared at -5 C and -20 C respectively. Micromorphology of the membranes was examined using scanning electron microscope.Degradation in 0.01M PBS solution for 30 days and porosity were compared.(2)L929 cells were co-cultured with the porous chitosan membranes and biocompatible observation was performed with scanning electron microscope.The tissuecompatibility was invesgated in animal study.(3)In the preliminary animal study,the porous chitosan membranes containing 10ng/ml TGF- β1 were applied as direct pulp caping in dog teeth,the reparation of pulp tissue at 3wk was observed.According to the preliminary study, the porous chitosan membranes containing different amount of TGF- β1 were further investingated.Result:(1)Asymmetric chitosan membranes including porous and dense layers were prepared by CIPS method.The size of poruses of membranes prepared at -5 C was about 50 m-100 m with regular structure. Porosity and degradation were 93.2% and 25.2% respectively; The size of poruses of membranes prepared at -20 C was about 100 m-400 m with irregular structure. Porosity and degradation were 78.2%(p<0.01)and 19.5%(p<0.05). (2)L929 cells could grow into the poruses and attach the material with globular morphology.These proved that cells can proliferate well in the prepared membranes. Tissue sections at 2wk after direct pulp capping in dog teeth showed that there were not obvious inflammatory reaction and necrosis in the pulp. (3)In the preliminary study,the pulp reparation were not abserved in the area of pulp exposure at 3wk after direct pulpcapping,while the tertiary detine could be found in the adjacent area.Conclusion:The porous chitosan membranes prepared at -5 C had regular structure,high porosity,suitable degradation and tissue compatablity which could be used as the vehicle of biological factors and release them regularly in direct pulp caping treatment.In the preliminary animal study,the pulp reparation could be observed in the adjacent area of pulp exposure using porous chitosan membranes containing 10ng/ml TGF- β1 as a kind of direct pulp capping material.