The Degradation Performance Of PLLA/PDLLA/5%HA Composites As Root Canal Post In Primary Teeth

Test.1 The Degradation Performance of PLLA/PDLLA/5%HA Composites As Root Canal Post In Primary TeethObjective:To evaluate the degradation of different proportions of the PLLA/PDLLA/5%HA composites in vitro,to find the ideal material of root canal post for primary teeth.Methods:in this experiment,according to the standard for biological evaluation of medical devices,according to the mass fraction of the PLLA/PDLLA/HA for 80/15/ 5,75/20/5,70/25/5 three groups and the neat PLLA(control group)were soaked in distilled water and phosphate buffer solution(PBS solution),a series of tests were performed with specimen in vitro at 2,4,6,8,10 months respectively to evaluate the degradation in vitro of PLLA/PDLLA/5%HA composites.Results:Gross observation: composites groups within 10 months were completely white,small micro cracks and peeling phenomenon;SEM showed that with time,there are four groups of material matrix pore and gradually become larger,HA particles of PLLA/ PDLLA/5%HA became smaller,detached from the surface of the substrate.At 10 th months,75%PLLA/20%PDLLA/5%HA and 70%PLLA/25%PDLLA/5%HA is observed the structure of PLA molding,showed disordered shape;Molecular Weight and Biological Degradation Rate: initial state each material,the weight average molecular weight difference,10 months the neat PLLA degradation rate reached 70.5%,79.6% for 80%PLLA/15%PDLLA/5%HA,75%PLLA/ 20%PDLLA/5%HA and 70%PLLA/25%PDLLA/5%HA reached 90%;Mechanical Properties with time,flexural strength and elastic modulus of all groups PLLA/PDLLA/5%HA composites and neat PLLA attenuation,and the attenuation the speed of composites faster than neat PLLA.At tenth months the 70%PLLA/25%PDLLA/5%HA has lost strength;pH value: with the degradation process,neat PLLA p H value is lower than PLLA/PDLLA/5%HA.Conclusion:early degradation rate of PLLA/PDLLA/5%HA composites is more slower than neat PLLA,is conducive to maintaining the material properties.In the observation period of 10 months,the degradation rate of 80%PLLA/15% PDLLA/5%HA is moderate,and the bending strength and elastic modulus also can meet the requirements of deciduous teeth bite force.Test.2 The Biological Effects on Osteoclasts of Different Ratio of PLLA/PDLLA/5%HA CompositeObjective:To observe the effect of different proportion of PLLA/PDLLA/5%HA complex effects of extracts on osteoclast biology properties.Methods:Inducing RAW264.7 cells to differentiate into osteoclasts in vitro RANKL,TRAP staining kit and identification of mature osteoclasts;MTT was used to observe the different proportions of PLLA/PDLLA/5%HA complex inhibitory effects of extracts from proliferation of osteoclasts in 1,3,5 days;observe the formation of bone resorption of PLLA/PDLLA/5%HA thin film by scanning electron microscopy.Results:TRAP staining after RANKL induced 5 days,there were more than 3 stained blue nuclei and fusion,red / red wine like osteoclasts.the PLA post extracts compared at each time point,the A value and the normal medium group showed no significant difference(P>0.05).The cytotoxicity grade was grade 0~1.Osteoclast formation without absorption lacunae on the PLA/HA film,did not change the surface morphology of the films.Conclusion: PLLA/HA Composite has good biological safety,and osteoclast resorption can not be formed on its surface.