title: Establishing Apical Patency: To be or not to be?
abstract: BACKGROUND
  The apical portion of the root canal is very complex and challenging during endodontic treatment. Root canal preparation and obturation to the apical constriction may provide the best prognosis. Incomplete debridement, foramen transportation, and inadequate seal in the apical portion are considered to be responsible for treatment failure. The technique "apical patency" is considered as a way for maintaining the apical part the free of the debris by recapitulation, using a small K-file through the area of the apical foramen. This term was firstly proposed by Buchanan. In this technique, the smallest diameter file is set 1 mm longer than working length and recapitulated after each instrument to prevent packing of debris in the apical part. Apical patency has been found to be effective in achieving an apical seal with gutta-percha. Teeth prepared with a step back method and with maintained apical patency may show less leakage when obturated with cold lateral condensation technique. Data regarding the effect of apical patency on the healing of periapical tissue are very scarce, and it has been shown that the patency file has detrimental effect on the healing of periapical tissues in animal studies. However, using patency file in endodontic treatment is controversial and further studies are needed. The purpose of this article is to review the effect of using a patency file on the extrusion of root canal contents, the apical seal, postoperative pain, and healing of periapical tissues. Furthermore, the effect of establishing patency on reaching irrigation solutions to the apical portion of the canal and prognosis of root canal treatment are discussed.
  
  
  CONCLUSIONS
  Keywords: Apical patency, Apical seal, Apical transportation, Postoperative pain, Prognosis.
authors.affiliation: Iranian Center for Endodontic Research, Research Institute of Dental Sciences, Shaheed Beheshti University of Medical Sciences, Iranian National Elite Foundation, Tehran, Islamic Republic of Iran.
authors.forename: Zahed
authors.initials: Z
authors.lastname: Mohammadi
authors.affiliation: Department of Endodontics, Dental Research Center, Faculty of Dentistry, Mashhad University of Medical Sciences, Mashhad Islamic Republic of Iran, Phone: +00985138829501, e-mail: jafarzadehbh@mums.ac.ir.
authors.forename: Hamid
authors.initials: H
authors.lastname: Jafarzadeh
authors.affiliation: Hamedan, Islamic Republic of Iran.
authors.forename: Sousan
authors.initials: S
authors.lastname: Shalavi
authors.affiliation: Department of Conservative Dentistry, Showa University Dental Hospital, Tokyo, Japan.
authors.forename: Jun-Ichiro
authors.initials: JI
authors.lastname: Kinoshita
mesh_terms: D006801:Humans; D011379:Prognosis; D019233:Retreatment; D018915:Root Canal Preparation / Q000379:methods; D012390:Root Canal Therapy; D019227:Tooth Apex / Q000033:anatomy & histology* / Q000473:pathology; D014076:Tooth Diseases / Q000175:diagnosis* / Q000473:pathology; D017211:Treatment Failure