title: Comparison of smear layer removal using the Nd:YAG laser, ultrasound, ProTaper Universal system, and CanalBrush methods: an in vitro study.
abstract: BACKGROUND
  The aim of this study was to compare the efficacy of the Nd:YAG laser, ultrasound, the ProTaper Universal system (Dentsply Maillefer, Ballaigues, Switzerland), and the CanalBrush (Coltene Whaledent, Langenau, Germany) methods for the removal of the smear layer from the apical third of root canals.
  
  
  METHODS
  Fifty distal root canals from extracted human mandibular first molars were instrumented up to ProTaper Universal F5 and divided randomly into 5 groups (n = 10) according to the following final irrigation agitation techniques: no agitation (control), ProTaper Universal file, ultrasound, CanalBrush, and Nd:YAG laser. Specimens were observed under a scanning electron microscope. The presence of the smear layer was evaluated using a 3-grade scoring system. The data were analyzed with Cohen kappa, Kruskal-Wallis, and Mann-Whitney U tests. A level of significance of .05 was adopted.
  
  
  RESULTS
  The ultrasound group performed significantly better than the rest of the groups; 56.6% of the specimens revealed no smear layer, 44.4% showed the presence of a moderate smear layer, and no heavy smear layers were observed. In the Nd:YAG laser group, 30% of the specimens presented with no smear layer, 70% showed the presence of a moderate smear layer, and no heavy smear layers were observed. In contrast, a heavy smear layer was observed on the surfaces of the root canals in the CanalBrush (23.4%), ProTaper Universal (13.4%), and control (86.6%) groups. Statistically significant differences were observed (P < .05).
  
  
  CONCLUSIONS
  None of the agitation methods completely removed the smear layer. However, the ultrasound method performed significantly better followed by the Nd:YAG laser, the CanalBrush, and the ProTaper Universal system. Agitation of the irrigant improved smear layer removal in the apical third of the canal.
authors.affiliation: Department of Prosthetics and Oral and Facial Surgery, Faculty of Dentistry, Federal University of Pernambuco, Recife, Brazil. Electronic address: gaga_lima@hotmail.com.
authors.forename: Grasiele Assis
authors.initials: GA
authors.lastname: da Costa Lima
authors.affiliation: Department of Prosthetics and Oral and Facial Surgery, Faculty of Dentistry, Federal University of Pernambuco, Recife, Brazil.
authors.forename: Carlos Menezes
authors.initials: CM
authors.lastname: Aguiar
authors.affiliation: Department of Prosthetics and Oral and Facial Surgery, Faculty of Dentistry, Federal University of Pernambuco, Recife, Brazil.
authors.forename: Andréa Cruz
authors.initials: AC
authors.lastname: Câmara
authors.affiliation: Department of Parasitology, Aggeu Magalhães Research Center, Fiocruz, Recife, Brazil.
authors.forename: Luiz Carlos
authors.initials: LC
authors.lastname: Alves
authors.affiliation: Department of Parasitology, Aggeu Magalhães Research Center, Fiocruz, Recife, Brazil.
authors.forename: Fábio André Brayner
authors.initials: FA
authors.lastname: Dos Santos
authors.affiliation: Department of Biology, Catholic University of Pernambuco, Recife, Brazil.
authors.forename: Aline Elesbão
authors.initials: AE
authors.lastname: do Nascimento
mesh_terms: D000293:Adolescent; D006801:Humans; D053844:Lasers, Solid-State; D018915:Root Canal Preparation / Q000379:methods*; D016369:Smear Layer / Q000000981:diagnostic imaging* / Q000473:pathology; D014070:Tooth / Q000000981:diagnostic imaging / Q000648:ultrastructure; D014099:Toothbrushing; D014465:Ultrasonics
keywords: EDTA; laser; smear layer; sodium hypochlorite; ultrasound