title: Counterclockwise or clockwise reciprocating motion for oval root canal preparation: a micro-CT analysis.
abstract: OBJECTIVE
  To evaluate oval root canal preparation using one or two instruments in counterclockwise or clockwise reciprocating motion.
  
  
  METHODS
  The radiographic diameter of mandibular human incisors was evaluated, and oval canals were selected (2 ≤ Diameter Ratio ≤ 4). Fifty-seven teeth were assigned to root canal preparation (n = 19): Reciproc 40 (R40) in a counterclockwise reciprocating motion; Mtwo size 40, .06 taper (M 40.06) in a clockwise reciprocating motion or Mtwo size 20, .06 taper and size 40, .06 taper (M 20/40.06) in a clockwise reciprocating motion. Mtwo instruments were coupled to an ENDO DUAL motor, turning 150° clockwise and 30° counterclockwise. Scanning was performed before and after root canal preparation using a SkyScan 1176 micro-computed tomography. Volume, percentage of debris and percentage of uninstrumented surface were analysed in the entire root canal and in each third of the canal. Data were compared using anova and Tukey's tests or Kruskal-Wallis and Dunn tests.
  
  
  RESULTS
  The Reciproc and Mtwo systems using different kinematics were associated with a similar increase in root canal volume. Additionally, both system had similar percentage of uninstrumented surface (P > 0.05). Mtwo size 20, .06 taper and size 40, .06 taper was associated with significantly lower debris (P < 0.05) in the middle third (0.56%) when compared to R40 (1.31%) and M size 40, .06 taper (1.54%).
  
  
  CONCLUSIONS
  The conventional reciprocation motion for R40 and the clockwise reciprocation motion for Mtwo resulted in similar root canal preparations. Less remaining debris was present in the middle third when two instruments with different diameters were used.
authors.affiliation: Department of Restorative Dentistry, Araraquara Dental School, São Paulo State University, Araraquara, São Paulo, Brazil.
authors.forename: C G
authors.initials: CG
authors.lastname: Espir
authors.affiliation: Department of Restorative Dentistry, Araraquara Dental School, São Paulo State University, Araraquara, São Paulo, Brazil.
authors.forename: C A
authors.initials: CA
authors.lastname: Nascimento-Mendes
authors.affiliation: Department of Restorative Dentistry, Araraquara Dental School, São Paulo State University, Araraquara, São Paulo, Brazil.
authors.forename: J M
authors.initials: JM
authors.lastname: Guerreiro-Tanomaru
authors.affiliation: Department of Dentistry, São Paulo Dental School, University of São Paulo, São Paulo, São Paulo, Brazil.
authors.forename: L G
authors.initials: LG
authors.lastname: Freire
authors.affiliation: Department of Dentistry, São Paulo Dental School, University of São Paulo, São Paulo, São Paulo, Brazil.
authors.forename: G
authors.initials: G
authors.lastname: Gavini
authors.affiliation: Department of Restorative Dentistry, Araraquara Dental School, São Paulo State University, Araraquara, São Paulo, Brazil.
authors.forename: M
authors.identifier: http://orcid.org/0000-0002-2574-4706
authors.initials: M
authors.lastname: Tanomaru-Filho
mesh_terms: D003786:Dental Pulp Cavity / Q000000981:diagnostic imaging / Q000601:surgery; D006801:Humans; D007180:Incisor / Q000000981:diagnostic imaging / Q000601:surgery; D018915:Root Canal Preparation / Q000295:instrumentation / Q000379:methods*; D012399:Rotation; D055114:X-Ray Microtomography
keywords: micro-computed tomography; reciprocating motion; root canal preparation