title: Dynamic movement of intracanal gas bubbles during cleaning and shaping procedures: the effect of maintaining apical patency on their presence in the middle and cervical thirds of human root canals-an in vivo study.
abstract: BACKGROUND
  The vapor lock effect has been shown to limit the penetration of irrigating solutions into the apical third of root canals both in vivo and in vitro; however, little attention has been given to gas bubbles in the remainder of the root canal system.
  
  
  METHODS
  Seventy-one human root canals were randomly divided into 4 groups. Apical patency was maintained in 2 groups in both small (PS) (n = 21) and big canals (PB) (n = 15) during shaping and cleaning procedures with a 10 K-file 1 mm beyond working length but not in the other 2 groups: no patency, small canals (NPS) (n = 19) and no patency, big canals (NPB) (n = 16). Irrigation was performed with 1 mL of a solution prepared with a radiopaque contrast medium and sodium hypochlorite 5.25%. Digital images were taken, and a calibrated reader determined the presence or absence of gas bubbles in the middle and cervical thirds of the root canal system.
  
  
  RESULTS
  When a patency file was not used, 40% of the root canals presented gas bubbles; when a patency file was used, 25% of the cases exhibited gas bubbles.
  
  
  CONCLUSIONS
  The presence of gas bubbles in the middle and cervical thirds of the root canal system during cleaning and shaping procedures is a common finding regardless of whether a patency file was used, although maintaining apical patency significantly leads to minimizing the presence of gas bubbles in big canals (P < .05).
authors.affiliation: University of Tlaxcala, Tlaxcala, Mexico. jveraro@yahoo.com.mx
authors.forename: Jorge
authors.initials: J
authors.lastname: Vera
authors.forename: Ana
authors.initials: A
authors.lastname: Arias
authors.forename: Mónica
authors.initials: M
authors.lastname: Romero
mesh_terms: D003287:Contrast Media; D003786:Dental Pulp Cavity / Q000033:anatomy & histology*; D004867:Equipment Design; D005740:Gases / Q000737:chemistry*; D006801:Humans; D009068:Movement; D019252:Radiography, Dental, Digital; D012388:Root Canal Irrigants / Q000008:administration & dosage; D018915:Root Canal Preparation / Q000295:instrumentation / Q000379:methods*; D012973:Sodium Hypochlorite / Q000008:administration & dosage; D019227:Tooth Apex / Q000033:anatomy & histology*; D055548:Vapor Pressure
chemical_list: D003287:Contrast Media; D005740:Gases; D012388:Root Canal Irrigants; D012973:Sodium Hypochlorite