title: Efficacy of Needle, Ultrasonic, and Endoactivator Irrigation and Photon-Induced Photoacoustic Streaming in Removing Calcium Hydroxide from the Main Canal and Isthmus: An In Vitro Micro-Computed Tomography and Scanning Electron Microscopy Study.
abstract: OBJECTIVE
  The aim of this in vitro study was to use high-resolution micro-computed tomography (micro-CT) and scanning electron microscopy (SEM) to compare the efficacy of four irrigation techniques [needle, ultrasonic, EndoActivator, and photon-induced photoacoustic streaming (PIPS)] in removing calcium hydroxide (Ca[OH]2) from the root canal and isthmus of maxillary premolars.
  
  
  METHODS
  Twenty-four maxillary first premolars were selected based on the presence of isthmus regions on micro-CT scans. Root canals were instrumented with an F2 file using ProTaper rotary instruments and filled with Ca(OH)2 paste. Samples were stored at 37°C and 100% humidity for 1 week and randomly divided into four groups (n=6 each), according to irrigation technique. Samples were scanned with micro-CT before instrumentation, after Ca(OH)2 filling, and after irrigation. Ca(OH)2 reduction in the coronal, middle, and apical thirds and in the isthmus were assessed with three-dimensional image analysis. Next, specimens were split longitudinally, and canal walls were examined with SEM for Ca(OH)2 residues. Data were statistically evaluated with the Kruskal-Wallis and Mann-Whitney tests (p=0.05).
  
  
  RESULTS
  The PIPS and ultrasonic groups showed greater Ca(OH)2 reduction in the apical third and higher cleanliness of the isthmus than the EndoActivator and needle irrigation groups (p<0.05). Ca(OH)2 residue scores in the PIPS and ultrasonic groups were significantly lower than those in the EndoActivator and needle groups in all regions of the root canals (p<0.05). There was no significant difference between PIPS and ultrasonic groups (p>0.05), or between EndoActivator and needle groups (p>0.05).
  
  
  CONCLUSIONS
  PIPS and ultrasonic irrigation more effectively removed Ca(OH)2 from the main canal and isthmus in maxillary premolars than did EndoActivator or needle irrigation.
authors.affiliation: 1 Department of Stomatology, Air Force General Hospital of the PLA , Haidian District, Beijing, China .|2 Comprehensive Dental Care, Endodontics, Faculty of Dentistry, The University of Hong Kong , Prince Philip Dental Hospital, Sai Ying Pun, Hong Kong, 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, Sai Ying Pun, Hong Kong, 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, Sai Ying Pun, Hong Kong, China .|3 VIP Dental Service & Geriatric Dentistry, School and Hospital of Stomatology, Peking University , Haidian District, Beijing, China .
authors.forename: Xingzhe
authors.initials: X
authors.lastname: Yin
authors.affiliation: 2 Comprehensive Dental Care, Endodontics, Faculty of Dentistry, The University of Hong Kong , Prince Philip Dental Hospital, Sai Ying Pun, Hong Kong, China .
authors.forename: Jeffrey Wen Wei
authors.initials: JW
authors.lastname: Chang
authors.affiliation: 1 Department of Stomatology, Air Force General Hospital of the PLA , Haidian District, Beijing, China .
authors.forename: Jie
authors.initials: J
authors.lastname: Ke
authors.affiliation: 2 Comprehensive Dental Care, Endodontics, Faculty of Dentistry, The University of Hong Kong , Prince Philip Dental Hospital, Sai Ying Pun, Hong Kong, China .
authors.forename: Chengfei
authors.initials: C
authors.lastname: Zhang
mesh_terms: D001641:Bicuspid / Q000737:chemistry*; D002126:Calcium Hydroxide / Q000032:analysis*; D003786:Dental Pulp Cavity / Q000737:chemistry*; D006801:Humans; D008437:Maxilla; D008855:Microscopy, Electron, Scanning; D061088:Photoacoustic Techniques; D007507:Therapeutic Irrigation / Q000379:methods*; D014057:Tomography, X-Ray Computed / Q000379:methods*; D014465:Ultrasonics
chemical_list: D002126:Calcium Hydroxide