title: Effectiveness of Sonic, Ultrasonic, and Photon-Induced Photoacoustic Streaming Activation of NaOCl on Filling Material Removal Following Retreatment in Oval Canal Anatomy.
abstract: OBJECTIVE
  This study aimed to assess the effectiveness of sonic, ultrasonic and laser [photon-induced photoacoustic streaming (PIPS)] irrigation activation in removing filling remnants from oval root canals after standard canal retreatment procedures with the ProTaper universal rotary retreatment system.
  
  
  METHODS
  Twenty-eight maxillary first premolars were instrumented with ProTaper NiTi rotary instruments and obturated with gutta-percha and AH Plus sealer using the continuous wave of condensation technique. After storage at 37°C and 100% humidity for 1 week, the specimens were retreated with the ProTaper universal retreatment system for the removal of filling material. Teeth were then randomly assigned into four groups (n = 7): group 1, positive control; group 2, retreated with sonic irrigation; group 3, retreated with ultrasonic irrigation; and group 4, retreated with laser irradiation. The specimens were scanned using micro-CT before instrumentation, after obturation and mechanical retreatment, and after additional activation procedures. The percentage volume of the filling remnants was measured. Specimens were split longitudinally after micro-CT scan, canal walls were examined using scanning electron microscopy (SEM), and the amount of residual filling material was scored.
  
  
  RESULTS
  The filling materials' removal efficacy in the three experimental groups was higher than that of the control group (p < 0.05), whereas filling materials ranging from 1.46 ± 0.30 to 2.21 ± 0.46 mm(3) remained in the canal in all three experimental groups. Additionally, there was a significantly greater reduction in the amount of filling remnants in the PIPS group than in the sonic and ultrasonic groups (both p < 0.05), and significantly greater reduction in the ultrasonic group than the sonic group (p < 0.05).
  
  
  CONCLUSIONS
  Activation of NaOCl with PIPS showed significantly better performance than sonic and ultrasonic techniques in removing the filling remnants following mechanical retreatment of oval root canals. The ultrasonic technique also performed better than the sonic technique. However, none of the additional activation procedures was able to completely eliminate the filling remnants.
authors.affiliation: 1 Department of Endodontics and Operative Dentistry I, School and Hospital of Stomatology, Fujian Medical University , Fujian, China .
authors.forename: Shan
authors.initials: S
authors.lastname: Jiang
authors.affiliation: 2 Comprehensive Dental Care, Endodontics, Faculty of Dentistry, The University of Hong Kong , Prince Philip Dental Hospital, Hong Kong SAR, China .
authors.forename: Ting
authors.initials: T
authors.lastname: Zou
authors.affiliation: 2 Comprehensive Dental Care, Endodontics, Faculty of Dentistry, The University of Hong Kong , Prince Philip Dental Hospital, Hong Kong SAR, China .|3 Department of Stomatology, Air Force General Hospital of the PLA , Haidian District, Beijing, China .
authors.forename: Dongxia
authors.initials: D
authors.lastname: Li
authors.affiliation: 2 Comprehensive Dental Care, Endodontics, Faculty of Dentistry, The University of Hong Kong , Prince Philip Dental Hospital, Hong Kong SAR, China .
authors.forename: Jeffery W W
authors.initials: JW
authors.lastname: Chang
authors.affiliation: 1 Department of Endodontics and Operative Dentistry I, School and Hospital of Stomatology, Fujian Medical University , Fujian, China .
authors.forename: Xiaojing
authors.initials: X
authors.lastname: Huang
authors.affiliation: 2 Comprehensive Dental Care, Endodontics, Faculty of Dentistry, The University of Hong Kong , Prince Philip Dental Hospital, Hong Kong SAR, China .
authors.forename: Chengfei
authors.initials: C
authors.lastname: Zhang
mesh_terms: D006171:Gutta-Percha; D006801:Humans; D053844:Lasers, Solid-State; D028022:Low-Level Light Therapy; D012387:Root Canal Filling Materials; D012389:Root Canal Obturation; D018915:Root Canal Preparation / Q000379:methods*; D046509:Tissue Culture Techniques; D000069453:Ultrasonic Waves; D055114:X-Ray Microtomography
chemical_list: D012387:Root Canal Filling Materials; D006171:Gutta-Percha