RESUMO
Objective:To study the bactericidal effect of ultrasonic technique combined with saline(SL),sodium hypochlorite(SH) or Koutai(KT) irrigation in root canal preparation. Methods:120 single-rooted teeth in 120 patients with chronic periapical periodontitis were divided into six groups randomly with 20 in each group.The tooth canal in group A, B and C were prepared with ultrasonic technique. SL, SH and KT were used to irrigate in the root canals group A,B and C respectively.Routine hand instruments were used in group A1, B1 and C1.SL, SH and KT were used as irrigations in group A1, B1 and C1 respectively.30 ?l of liquid sample was obtained from each root canal and examined for anaerobic bacteria colony counting before and after root canal preparation. Result:After root canal preparation the number of anaerobic bacteria colony was significantly reduced in all the 6 groups(P