title: Comparison of the force required to fracture roots vertically after ultrasonic and Masserann removal of broken instruments.
abstract: OBJECTIVE
  To evaluate the force required to fracture roots vertically after the removal of broken instruments using ultrasonic tips and a Masserann kit.
  
  
  METHODS
  Thirty-nine extracted human anterior teeth with single and straight roots were used. The crown of each tooth was removed until the full length of the tooth was 13 mm. All canals were instrumented with the step-back technique to a size 25 K-file. The teeth were randomly divided into three groups: two experimental groups and a control group. The size 30 K-files used for the test were notched to a depth of half of the instrument with a No. 2 round bur at a point 3 mm from the tip to facilitate breakage of the file at this point. The fractured instruments were removed from the canals using ultrasonic tips or a Masserann kit. The samples were subjected to a continual vertical loading, using a universal testing machine. For each root, the force at the time of fracture was recorded in Newtons. The results were analysed statistically using one-way anova and Tukey HSD test.
  
  
  RESULTS
  The force required to fracture the roots vertically was significantly higher in the control group than the experimental groups (P < 0.01). The roots from which the broken instruments had been removed using ultrasonic tips required more force to fracture than roots in the Masserann group; however, the difference was not statistically significant.
  
  
  CONCLUSIONS
  Removal of a fractured instrument from the middle third of the root decreased the force required to fracture the root vertically, regardless of the technique used for instrument removal. There was not difference between the ultrasonic technique and the Masserann technique.
authors.affiliation: Department of Endodontics, Yeditepe University Faculty of Dentistry, İstanbul, Turkey. muzeyyengerek@yahoo.com
authors.forename: M
authors.initials: M
authors.lastname: Gerek
authors.forename: E D
authors.initials: ED
authors.lastname: Başer
authors.forename: M B
authors.initials: MB
authors.lastname: Kayahan
authors.forename: H
authors.initials: H
authors.lastname: Sunay
authors.forename: R F
authors.initials: RF
authors.lastname: Kaptan
authors.forename: G
authors.initials: G
authors.lastname: Bayırlı
mesh_terms: D001696:Biomechanical Phenomena; D003786:Dental Pulp Cavity / Q000473:pathology; D003799:Dental Stress Analysis / Q000295:instrumentation; D003804:Dentin / Q000473:pathology; D004492:Edetic Acid / Q000627:therapeutic use; D004867:Equipment Design; D004868:Equipment Failure; D005547:Foreign Bodies / Q000209:etiology / Q000628:therapy*; D006801:Humans; D007440:Intubation / Q000295:instrumentation; D008422:Materials Testing; D008853:Microscopy / Q000295:instrumentation; D012388:Root Canal Irrigants / Q000627:therapeutic use; D018915:Root Canal Preparation / Q000295:instrumentation*; D012399:Rotation; D013314:Stress, Mechanical; D014082:Tooth Fractures / Q000503:physiopathology*; D014092:Tooth Root / Q000473:pathology*; D014465:Ultrasonics / Q000295:instrumentation; D014732:Vibration / Q000627:therapeutic use
chemical_list: D012388:Root Canal Irrigants; D004492:Edetic Acid