Study On The Effect Of Ultrasonic Therapy On The Deactivation And Elimination Of Root Canal Endotoxin

Aim:Periapical periodontitis is caused mainly by bacteria and their products of metabolism, which exist steadily in the root canal and can reach the periapical tissues through the apical foramen and collateral vessel. G^- anaerobic bacteria are the dominant bacteria in the infected root canal. They can directly poison tissues and cells or indirectly damage periapical tissues by evoking inflammation and immune reaction. Lipopolysaccharide(LPS), produced by G^- anaerobic bacteria, is one of generally recognized as inflammatory factors and plays an important role in the development of periapical periodontitis. LPS can stimulate immunological cell to excrete cytokines,such as TNF-α ,IL-1β and PGE₂, which can cause tissue dissolution and bone resorption.How to remove the endotoxin of root canal effectively is an important link of the root canal therapy. The bacteria killing potency of ultrasonic device for root canal therapy was already confirmed, but the effect on endotoxin is not yet known. In this study,we tested the endotoxin concentration in each man-made glass root canal and each root canal of chronic periapical periodontitis by kinetic turbidimetric Limulus test after ultrasonic treatment and analyzed the role of ultrasonic treatment in deactivating and eliminating the root canal endotoxin. Methods:This study included four partsPart 1. Study on the deactivation of the standard endotoxin in man-made glass root canals with different time ultrasonic vibrationA total of 40 man-made glass root canals were randomly divided into 4 groups as ultrasonic vibration of 5 minutes,7 minutes, 10 minutes and the control(0 minute).60ul standard endotoxin solution of 1EU/ml concentration was poured into each root canal.Different time's ultrasonic vibration were given to different groups. After ultrasonic vibration, the endotoxin concentration in each man-made glass root canal was tested by kinetic turbidimetric limulus test and statistical treatment was done to see if there was significant diference inter-group and to investigate the effect of only ultrasonic vibration on the root canal endotoxin as well as the time factor influence.Part 2.Study on the deactivation of the standard endotoxin in man-made glass root canals with ultrasonic vibration together with different root canal rinse solutionA total of 50 man-made glass root canals were randomly divided into 5 groups as ultrasonic vibration together with 3%H₂O₂ solution,only 3%H₂O₂ solution, ultrasonic vibration together with 5.25%NaCLO solution, only 5.25%NaCLO solution and the control .60ul mixture of standard endotoxin solution mixed with 3%H₂O₂ solution or 5.25%NaCLO solution was poured into each man-made glass root canal of the first four groups and 60ul standard endotoxin solution into the control.The initial concentration of standard endotoxin solution of all the groups was the same as 1EU/ml. Except for additional 5 minutes' ultrasonic vibration given to group A and C,all the samples were placed in a static position for 60 minutes. After the experimentation , the endotoxin concentration in each man-made glass root canal was tested by kinetic turbidimetric limulus test and statistical treatment was done to see if there was significant diference inter-group and to investigate the effects of synergism of ultrasonic vibration and the root canal rinse solution in deactivating the root canal endotoxin.Part 3.Study on the deactivation of the endotoxin in root canals of extracted teeth with ultrasonic vibration together with root canal rinse solution10 maxillary premolars with 2 root canals extracted because of serious chronic periapical periodontitis were prepared with modified double-flared technique with apical foramen sealed . 30ul 3%H₂O₂ solution were poured into each root canal of the teeth and 2 minutes ultrasonic vibration were given. Samples were taken before and after ultrasonic vibration and the endotoxin concentration of them was tested by kinetic turbidimetric Limulus test. Statistical treatment was done to see if there was significant diference inter-group and to investigate the effect of synergism of ultrasonic vibration and the root canal rinse solution in deactivating the endotoxin in complicated root canal system.Part 4.Study on the effect of ultrasonic irrigation in eliminating the endotoxin in the root canals of chronic periapical periodontitis10 maxillary premolars of chronic periapical periodontitis due to pulp necrosis of 10 patients were selected in the test. The root canals of them were opened conventionally and prepared with modified double-flared technique, followed by 2 minutes ultrasonic irrigation with asepsis distilled water given to each root canal. Samples were taken before, after root canal preparation and after ultrasonic irrigation and the endotoxin concentration of them was tested by kinetic turbidimetric limulus test. Statistical treatment was done to see if there was significant diference inter-group and to investigate the effect of ultrasonic irrigation in eliminating the endotoxin in the root canals of chronic periapical periodontitis.The data were analyzed statisticallv by One way—ANOVA, Kruskal-Wallis Test and Wilcoxon Signed Ranks Test of SPSS 11.5. Results:1. Study of man-made glass root canals:There were no significant differences of the endotoxin concentration inter the groups of different time ultrasonic vibration and the control (P>0.05).2. Study of man-made glass root canals :There was great statistical difference of the endotoxin concentration between each group of the test and the control(P<0.001) . The endotoxin concentration of the test was significantly lower than the control.There was no significant difference of the endotoxin concentration between the group of only 3%H₂O₂ solution and the group of ultrasonic vibration together with 3%H₂O₂ solution (P>0.05). There was no significant difference of the endotoxin concentration between the group of only 5.25%NaCLO solution and the group of ultrasonic vibration together with 5.25%NaCLO solution (P>0.05) . 3. Study of extracted teeth :There was great statistical difference of the endotoxin concentration before and after ultrasonic vibration (P<0.01) . The endotoxin concentration after ultrasonic vibration was significantly higher than the before.4. Clinical study:There was great statistical difference of the endotoxin concentration before and after root canal preparation (P<0.01 ) . After the preparation, the endotoxin concentration drops obviously. There was great statistical diference of the endotoxin concentration before and after ultrasonic irrigation (P<0.01) . After ultrasonic irrigation, the endotoxin concentration drops obviously.Conclusionsu Under the condition of this study,the only ultrasonic vibration of ultrasonic device for root canal therapy can not deactivate the endotoxin of infected root canals, and can not intensify the effect of root canal rinse solution in deactivating the endotoxin of infected root canals .But the ultrasonic irrigation may intensify the effect of the root canal rinse solution in eliminating the endotoxin of infected root canals.