title: In vitro study of calcium hydroxide removal from mandibular molar root canals.
abstract: BACKGROUND
  Previous studies have shown the difficulty in removing calcium hydroxide (Ca[OH]2) paste from the root canals before root filling.
  
  
  METHODS
  Mesial and distal canals of 30 mandibular molars were prepared with the WaveOne Primary (25/.08) and Large file (40/.08) (Dentsply Tulsa Dental Specialties, Tulsa, OK), respectively. All canals were then filled with Ca(OH)2. The teeth were divided into the following 3 treatment groups (each with n = 10): (1) instrumentation with needle irrigation, (2) instrumentation with irrigation and passive ultrasonic activation (PUI), and (3) the GentleWave system (Sonendo, Inc, Laguna Hills, CA) without instrumentation. The irrigation time in each group was 7.5 minutes. To further test the efficiency of the GentleWave system, shorter times of 90 seconds were tested using water alone. Reconstructed micro-computed tomographic scans were used to measure the volume of the canals and Ca(OH)2 after instrumentation, initial filling of Ca(OH)2, and after its removal. The percentage of Ca(OH)2 remaining in the canals was calculated.
  
  
  RESULTS
  None of the 10 teeth (30 canals) in the conventional irrigation and PUI groups were completely cleaned of Ca(OH)2 in 7.5 minutes. In the apical third of mesial and distal canals, respectively, conventional irrigation removed 47.82% ± 16.36% and 77.68% ± 12.82%, PUI removed 61.66% ± 25.54% and 88.85 ± 12.06%, and the GentleWave system removed significantly more Ca(OH)2 (P < .05) with 100% and 98.78% ± 3.84%. Additional experiments in 10 teeth, using only water as the irrigant, revealed that the GentleWave system removed 99.85% and 99.97% of Ca(OH)2 within 90 seconds without the use of any instruments in the mesial and distal canals, respectively.
  
  
  CONCLUSIONS
  The study confirms the difficulty to remove Ca(OH)2 from root canals using conventional methods. The GentleWave system removed the paste within 90 seconds using water irrigation alone.
authors.affiliation: Department of Stomatology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.
authors.forename: Jingzhi
authors.initials: J
authors.lastname: Ma
authors.affiliation: Division of Endodontics, Department of Oral Biological and Medical Sciences, Faculty of Dentistry, The University of British Columbia, Vancouver, Canada; Department of Materials Engineering, The University of British Columbia, Vancouver, Canada.
authors.forename: Ya
authors.initials: Y
authors.lastname: Shen
authors.affiliation: Department of Stomatology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China; Division of Endodontics, Department of Oral Biological and Medical Sciences, Faculty of Dentistry, The University of British Columbia, Vancouver, Canada.
authors.forename: Yan
authors.initials: Y
authors.lastname: Yang
authors.affiliation: State Key Laboratory of Oral Diseases, West China College and Hospital of Stomatology, Sichuan University, Chengdu, China.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Gao
authors.affiliation: Department of Stomatology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.
authors.forename: Pan
authors.initials: P
authors.lastname: Wan
authors.affiliation: Department of Stomatology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Gan
authors.affiliation: Sonendo Inc, Laguna Hills, California.
authors.forename: Payal
authors.initials: P
authors.lastname: Patel
authors.affiliation: Sonendo Inc, Laguna Hills, California.
authors.forename: Allison
authors.initials: A
authors.lastname: Curtis
authors.affiliation: Sonendo Inc, Laguna Hills, California.
authors.forename: Mehrzad
authors.initials: M
authors.lastname: Khakpour
authors.affiliation: Division of Endodontics, Department of Oral Biological and Medical Sciences, Faculty of Dentistry, The University of British Columbia, Vancouver, Canada. Electronic address: markush@dentistry.ubc.ca.
authors.forename: Markus
authors.initials: M
authors.lastname: Haapasalo
mesh_terms: D002126:Calcium Hydroxide / Q000302:isolation & purification*; D003786:Dental Pulp Cavity; D006801:Humans; D008963:Molar; D012390:Root Canal Therapy / Q000295:instrumentation / Q000379:methods*; D007507:Therapeutic Irrigation; D014465:Ultrasonics
chemical_list: D002126:Calcium Hydroxide
keywords: Calcium hydroxide; GentleWave; irrigation; root canal; ultrasound