title: Impact of needle insertion depth on the removal of hard-tissue debris.
abstract: OBJECTIVE
  To evaluate the effect of depth of insertion of an irrigation needle tip on the removal of hard-tissue debris using micro-computed tomographic (micro-CT) imaging.
  
  
  METHODS
  Twenty isthmus-containing mesial roots of mandibular molars were anatomically matched based on similar morphological dimensions using micro-CT evaluation and assigned to two groups (n = 10), according to the depth of the irrigation needle tip during biomechanical preparation: 1 or 5 mm short of the working length (WL). The preparation was performed with Reciproc R25 file (tip size 25, .08 taper) and 5.25% NaOCl as irrigant. The final rinse was 17% EDTA followed by bidistilled water. Then, specimens were scanned again, and the matched images of the canals, before and after preparation, were examined to quantify the amount of hard-tissue debris, expressed as the percentage volume of the initial root canal volume. Data were compared statistically using the Mann-Whitney U-test.
  
  
  RESULTS
  None of the tested needle insertion depths yielded root canals completely free from hard-tissue debris. The insertion depth exerted a significant influence on debris removal, with a significant reduction in the percentage volume of hard-tissue debris when the needle was inserted 1 mm short of the WL (P < 0.05).
  
  
  CONCLUSIONS
  The insertion depth of irrigation needles significantly influenced the removal of hard-tissue debris. A needle tip positioned 1 mm short of the WL resulted in percentage levels of hard-tissue debris removal almost three times higher than when positioned 5 mm from the WL.
authors.affiliation: Department of Dental Clinics, Rio de Janeiro State University, Rio de Janeiro, Brazil.
authors.forename: R
authors.identifier: http://orcid.org/0000-0003-2192-0124
authors.initials: R
authors.lastname: Perez
authors.affiliation: Department of Pediatric Dentistry and Orthodontics, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil.
authors.forename: A A
authors.initials: AA
authors.lastname: Neves
authors.affiliation: Department of Endodontics, Fluminense Federal University, Niterói, Rio de Janeiro, Brazil.
authors.forename: F G
authors.identifier: http://orcid.org/0000-0001-9972-6861
authors.initials: FG
authors.lastname: Belladonna
authors.affiliation: Department of Endodontics, Grande Rio University, Duque de Caxias, Rio de Janeiro, Brazil.
authors.forename: E J N L
authors.initials: EJNL
authors.lastname: Silva
authors.affiliation: Department of Dentistry II, Federal University of Maranhão, São Luís, Maranhão, Brazil.
authors.forename: E M
authors.initials: EM
authors.lastname: Souza
authors.affiliation: Department of Dental Clinics, Rio de Janeiro State University, Rio de Janeiro, Brazil.
authors.forename: S
authors.initials: S
authors.lastname: Fidel
authors.affiliation: Department of Restorative Dentistry, Dental School of Ribeirão Preto, University of São Paulo, São Paulo, Brazil.
authors.forename: M A
authors.initials: MA
authors.lastname: Versiani
authors.affiliation: Nuclear Engineering Program, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil.
authors.forename: I
authors.initials: I
authors.lastname: Lima
authors.affiliation: Department of Endodontics, Grande Rio University, Duque de Caxias, Rio de Janeiro, Brazil.
authors.forename: C
authors.initials: C
authors.lastname: Carvalho
authors.affiliation: Department of Endodontics, Grande Rio University, Duque de Caxias, Rio de Janeiro, Brazil.
authors.forename: G
authors.initials: G
authors.lastname: De-Deus
mesh_terms: D003786:Dental Pulp Cavity / Q000000981:diagnostic imaging / Q000601:surgery; D006801:Humans; D008963:Molar / Q000000981:diagnostic imaging / Q000601:surgery; D009339:Needles; D018915:Root Canal Preparation / Q000379:methods*; D007507:Therapeutic Irrigation / Q000295:instrumentation / Q000379:methods; D055114:X-Ray Microtomography
keywords: Reciproc; hard-tissue debris; insertion depth; irrigation; micro-CT; side-vented needle