Abstract:

Objective To study the effect of ultrasonic irrigation in deactivating and eliminating the endotoxin in the root canals of chronic periapical periodontitis. Methods 10 maxillary premolars with 2 root canals extracted because of serious chronic periapical periodontitis were opened conventionally and prepared with modified double-flared technique with apical foramen sealed. 30 μL 3% H2O2 solution was introduced into each root canal and 2 minutes ultrasonic vibration was given. Samples were taken before and after ultrasonic vibration. 10 maxillary premolars with 2 root canals of chronic periapical periodontitis of 10 patients in clinic were selected. The root canals of them were instrumented as above, followed by 2 minutes ultrasonic irrigation with asepsis distilled water. Samples were taken before, after root canal preparation and after ultrasonic irrigation. The endotoxin activity of them was tested by kinetic turbidimetric limulus test. Results The mean endotoxin activity of extracted premolars before ultrasonic vibration was 4.069 EU·mL-1 while after ultrasonic vibration it was 16.410 EU·mL-1. There was great statistical difference between them（P<0.01）. The endotoxin activity after ultrasonic vibration was significantly higher than that of before vibration. The clinically mean endotoxin activity before, after root canal preparation and after ultrasonic irrigation were 44.860, 4.099, and 0.116 EU·mL-1 respectively. There was great statistical difference between the endotoxin activity  before and after root canal preparation（P<0.01）. After the preparation, the endotoxin activity droped obviously. There was great statistical difference between the endotoxin activity before and after ultrasonic irrigation（P<0.01）. After ultrasonic irrigation, the endotoxin activity droped obviously. Conclusion Under the condition of simulating clinical work presence, the ultrasonic irrigation can not intensify the effect of the root canal rinse solution in deactivating the endotoxin of infected root canals, but it may intensify the effect of the root canal rinse solution in eliminating the endotoxin of infected root canals.

Key words: chronic periapical periodontitis, root canal preparation, ultrasonic irrigation, endotoxin, kinetic turbidimetric limulus test