title: Shaping ability and cleaning effectiveness of two single-file systems in severely curved root canals of extracted teeth: Reciproc and WaveOne versus Mtwo and ProTaper.
abstract: OBJECTIVE
  To compare shaping ability and cleaning effectiveness of two reciprocating single-file systems with Mtwo and ProTaper rotary instruments during the preparation of curved root canals in extracted teeth.
  
  
  METHODS
  A total of 80 root canals with curvatures ranging between 25° and 39° were divided into four groups of 20 canals. Based on radiographs taken prior to instrumentation, the groups were balanced with respect to the angle and the radius of canal curvature. Canals were prepared to the following apical sizes: Mtwo: size 35 using the single-length technique; ProTaper: F3, instruments were used in a modified crown-down manner; Reciproc and WaveOne: size 25. Using pre- and post-instrumentation radiographs, straightening of the canal curvatures was determined with a computer image analysis program. Preparation time and instrument failures were also recorded. These data were analysed statistically using anova and Student-Newman-Keuls test. The amounts of debris and smear layer were quantified on the basis of a numerical evaluation scale and were analysed statistically using the Kruskal-Wallis test.
  
  
  RESULTS
  During preparation no file fractured. All instruments maintained the original canal curvature well with no significant differences between the different files (P = 0.382). Instrumentation with Reciproc was significantly faster than with all other instruments (P < 0.05), while WaveOne was significantly faster than Mtwo and ProTaper (P < 0.05). For debris removal, Mtwo and Reciproc instruments achieved significantly better results (P < 0.05) than the other instruments in the apical third of the canals. In the middle and coronal parts, no significant differences were obtained between Mtwo, Reciproc and WaveOne (P > 0.05), while ProTaper showed significantly more residual debris (P < 0.05). The results for remaining smear layer were similar and not significantly different for the different parts of the canals (P > 0.05).
  
  
  CONCLUSIONS
  Under the conditions of this study, all instruments maintained the original canal curvature well and were safe to use. The use of Mtwo and Reciproc instruments resulted in better canal cleanliness in the apical part compared with ProTaper and WaveOne.
authors.affiliation: Central Interdisciplinary Ambulance in the School of Dentistry, University of Münster, Münster, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Bürklein
authors.forename: K
authors.initials: K
authors.lastname: Hinschitza
authors.forename: T
authors.initials: T
authors.lastname: Dammaschke
authors.forename: E
authors.initials: E
authors.lastname: Schäfer
mesh_terms: D003786:Dental Pulp Cavity / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D003804:Dentin / Q000033:anatomy & histology; D004867:Equipment Design; D004868:Equipment Failure; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008422:Materials Testing; D011859:Radiography; D018915:Root Canal Preparation / Q000295:instrumentation* / Q000379:methods / Q000592:standards; D012399:Rotation; D016369:Smear Layer; D013499:Surface Properties; D013997:Time Factors; D019227:Tooth Apex / Q000033:anatomy & histology; D019237:Tooth Cervix / Q000033:anatomy & histology; D019415:Torque