title: The effect of reciprocation versus rotational movement on the incidence of root defects during retreatment procedures.
abstract: OBJECTIVE
  To compare the incidence of dentinal defects caused by reciprocating and rotary techniques during retreatment procedures.
  
  
  METHODS
  One hundred and twenty extracted mandibular premolars with single canals were selected. Twenty teeth were left unprepared. The root canals in the remaining 100 teeth were prepared with K-files up to size 35 and filled with Gutta-percha and AH Plus sealer using a passive cold lateral compaction technique. Twenty canals were filled and received no further treatment. Eighty teeth were divided into four groups (n = 20 in each) to undergo the removal of the root filling. In groups 1 and 2, the root filling was removed using ProTaper Retreatment files and Reciproc files, respectively, and the canals were not refilled. In groups 3 and 4, the root filling was removed using ProTaper Retreatment files and Reciproc files, respectively, and the canals were then refilled using a conventional cold lateral compaction technique. The roots were sectioned horizontally at 3, 6 and 9 mm from the root apex and observed under a stereomicroscope at 20× magnification. Defects were categorized as no defect, incomplete defect and fracture. The differences between the groups were analysed using the chi-square exact test (P = 0.05).
  
  
  RESULTS
  No defects were observed in the unprepared and filled groups, in contrast to the experimental groups. In the coronal thirds, groups 2 and 4 had more dentinal defects than groups 1 and 3 (P < 0.05). In the middle thirds, group 4 had more defects than group 1 (P < 0.05). In the apical thirds, group 2 had fewer defects than did group 3 and group 4. Also, group 3 had more defects than group 1 (P < 0.05). When comparing the experimental groups, there were no significant differences with regard to fracture (P > 0.05).
  
  
  CONCLUSIONS
  Both nickel-titanium systems were associated with dentinal defects during retreatment procedures in extracted premolar teeth.
authors.affiliation: Department of Endodontics, Faculty of Dentistry, Erciyes University, Kayseri, Turkey.
authors.forename: Y
authors.initials: Y
authors.lastname: Üstün
authors.affiliation: Department of Endodontics, Faculty of Dentistry, Erciyes University, Kayseri, Turkey.
authors.forename: H S
authors.initials: HS
authors.lastname: Topçuoğlu
authors.affiliation: Department of Endodontics, Faculty of Dentistry, Erciyes University, Kayseri, Turkey.
authors.forename: S
authors.initials: S
authors.lastname: Düzgün
authors.affiliation: Department of Endodontics, Faculty of Dentistry, Erciyes University, Kayseri, Turkey.
authors.forename: B
authors.initials: B
authors.lastname: Kesim
mesh_terms: D001641:Bicuspid; D003762:Dental Instruments; D003804:Dentin / Q000293:injuries*; D004853:Epoxy Resins; D006171:Gutta-Percha; D006801:Humans; D066298:In Vitro Techniques; D008422:Materials Testing; D009532:Nickel; D019233:Retreatment; D012387:Root Canal Filling Materials; D018915:Root Canal Preparation / Q000295:instrumentation / Q000379:methods*; D014025:Titanium; D014082:Tooth Fractures / Q000209:etiology*
chemical_list: D004853:Epoxy Resins; D012387:Root Canal Filling Materials; C534916:epoxy resin-based root canal sealer; C040654:titanium nickelide; D009532:Nickel; D006171:Gutta-Percha; D014025:Titanium
keywords: cracks; dentine defects; reciprocation; retreatment; rotary