title: ProTaper rotary instrument fracture during root canal preparation: a comparison between rotary and hybrid techniques.
abstract: OBJECTIVE
  This study aimed to compare the frequency of ProTaper rotary instrument fracture with rotary (conventional) and hybrid (rotary and hand files) canal preparation techniques. Secondary objectives were to determine whether there was an association of ProTaper file fracture with the canal curvature and to compare the mean time required for canal preparation in the two techniques.
  
  
  METHODS
  An in vitro experiment was conducted on 216 buccal canals of extracted maxillary and mandibular first molars. After creating an access cavity and a glide path for each canal, a periapical radiograph was taken and the canal curvature was measured with Schneider's technique. The canals were then randomly divided into Group A (rotary technique) and Group B (hybrid technique). The length of ProTaper files were measured before and after each canal preparation. Time taken for each canal preparation was recorded.
  
  
  RESULTS
  A total of seven ProTaper files fractured in Group A (P=0.014) in canals with a curvature >25 degrees (P<0.001). The mean time taken for preparation of the root canals was 104.04 sec (± 55.7 sec) in Group A versus 122.88 sec (± 41.67 sec) in Group B (P=0.007).
  
  
  CONCLUSIONS
  In the teeth studied, the hybrid technique of root canal preparation with ProTaper rotary files, although time consuming, was safer in canals having a curvature greater than 25 degrees.
authors.affiliation: The Aga Khan University Hospital, Stadium Road, Karachi, 74800 Pakistan. huma.farid@aku.edu
authors.forename: Huma
authors.initials: H
authors.lastname: Farid
authors.forename: Farhan Raza
authors.initials: FR
authors.lastname: Khan
authors.forename: Munawar
authors.initials: M
authors.lastname: Rahman
mesh_terms: D000293:Adolescent; D000328:Adult; D003722:Dental Alloys / Q000737:chemistry; D003786:Dental Pulp Cavity / Q000000981:diagnostic imaging / Q000473:pathology; D004492:Edetic Acid / Q000008:administration & dosage; D004868:Equipment Failure; D019544:Equipment Failure Analysis; D006801:Humans; D008422:Materials Testing; D008963:Molar / Q000000981:diagnostic imaging / Q000473:pathology; D009532:Nickel / Q000737:chemistry; D016300:Radiography, Bitewing; D012388:Root Canal Irrigants / Q000008:administration & dosage; D018915:Root Canal Preparation / Q000295:instrumentation* / Q000379:methods; D012399:Rotation; D012973:Sodium Hypochlorite / Q000008:administration & dosage; D013193:Stainless Steel / Q000737:chemistry; D013997:Time Factors; D014025:Titanium / Q000737:chemistry; D019227:Tooth Apex / Q000000981:diagnostic imaging / Q000473:pathology; D055815:Young Adult
chemical_list: D003722:Dental Alloys; D012388:Root Canal Irrigants; C040654:titanium nickelide; D013193:Stainless Steel; D009532:Nickel; D004492:Edetic Acid; D014025:Titanium; D012973:Sodium Hypochlorite