Vitro Degradation Staudy Of Polylatic Acid Absorbable Posts And Films

Part 1 Vitro degradation study of polylatic acid absorbable postObjective: To evaluate the vitro degradation rate of the polylatic acid (PLA)absorbable post and try to find a kind of root canal fixation material which can be synchronously absorbed with the primary root absorption, to provide evidence for its clinical use.Means and methods: Forty PLA absorbable posts was weighted and divided into 4 groups randomly and 10 posts each. Then every group was put into one bottle which was filled with O.Olmol/L, PH7.4 PBS. All the groups should be placed in an incubator which was set at 37±1)?. Ten posts in one group were randomly selected at every stage (4 weeks,8 weeks, 16 weeks and 24 weeks)and marked as group A (4 weeks), group B (8 weeks), group C (16 weeks) and group D (24 weeks), meanwhile group E which wasn't soaked in the PBS was marked as control group .Then the selected posts were dried and weighted. The degradation rate (DR) of the posts was calculated and all data were analyzed by one-way ANOVA .Results: A statistically significant difference of weights of the posts was found among the four groups (P<0.01). The posts degraded for 24 weeks group were the least weighted with (0.0125 ± 0.0034 ) g,and the DR was 22.1 % which was significant greater than the other groups(P<0.01).Conclusion: The polylatic acid (PLA) absorbable post will be degraded significantly after 6 months in vitro.Part2.Vitro degradation microleakage study of polylatic acid absorbable posts and filmsObjective: To investigate the degradation of PLA absorbable posts and films by evaluating the root apical microleakage in vitro situation, and to provide evidence for the clinical use .Means and methods: Twenty-five single-canaled extracted upper central incisors were selected and prepared for the root canals treatment. Then they were get ready for the space post and filled with PLA absorbable posts and membranes. The apical area of the sample teeth was cut and crown area was restored with resin. All the samples were placed into 0.11mol/L, PH7.4 PBS. All the samples should be placed in an incubator which was set at 37±1)?. Five samples were selected randomly at every stage (4 weeks, 8weeks, 16weeks, 24 weeks) and marked as group A (4 weeks), group B (8 weeks), group C (16 weeks) and group D (24 weeks), meanwhile group E which wasn't soaked in the PBS was marked as control group. Then all the samples were soaked into the Indian ink for 72 hours and splited into two parts along a longitudinal bucca-to-lingual direction. A stereomicroscope was used to evaluate the deepest length of dye penetration . The one-way ANOVA test was used measure the distance whicho determine intergroup difference.Results: A statistically significant difference of microleakage was found among the different point times of the groups (P<0.01) . The microleakage of PLA absorbable posts and films in 24 weeks group was ( 6.98 ± 0.25 ) mm and significant greater than the other groups (P<0.01).Conclusions: The sealing capability of PL A absorbable posts and films will be decreased and degraded significantly after 6 months in vitro.