title: Defects in nickel-titanium instruments after clinical use. Part 1: Relationship between observed imperfections and factors leading to such defects in a cohort study.
abstract: The purpose of this study was to examine three different types of nickel-titanium (NiTi) systems (ProTaper [Dentsply Maillefer, Ballaigues, Switzerland], ProTaper for Hand Use [Dentsply Maillefer], and K3 [SybronEndo, Orange, CA]) that were discarded by 3 endodontic clinics. The instruments were evaluated for defects and factors leading to instrument deformation or fracture. A total of 1682 instruments were collected over 16 months and were examined. The location of the defect, if any, was recorded. The overall prevalence of unwinding defects was 3% and fracture 5%; the rates differed significantly between clinics. For one brand (ProTaper) used at two different clinics, a defect rate (fracture and distortion combined) of 7% (clinic A) vs. 13% (clinic B) for Shaping files (P < 0.05), and about 4% vs. 10% for Finishing files (P < 0.05) was observed. Fragments of broken Shaping file were significantly longer in clinic A than for clinic B (P < 0.05). The lowest defect rate was found for K3 instruments: unwinding 1%, and fracture 3%. It was concluded that the defect rates of NiTi instruments were influenced by such factors as the operator, preparation technique and instrument design.
authors.affiliation: Division of Endodontics, Department of Oral Biological and Medical Sciences, Faculty of Dentistry, University of British Columbia, Vancouver, Canada.
authors.forename: Ya
authors.initials: Y
authors.lastname: Shen
authors.forename: Markus
authors.initials: M
authors.lastname: Haapasalo
authors.forename: Gary Shun-Pan
authors.initials: GS
authors.lastname: Cheung
authors.forename: Bin
authors.initials: B
authors.lastname: Peng
mesh_terms: D015331:Cohort Studies; D003722:Dental Alloys; D003762:Dental Instruments; D003799:Dental Stress Analysis; D019544:Equipment Failure Analysis; D017743:Equipment Reuse; D009532:Nickel; D018915:Root Canal Preparation / Q000295:instrumentation*; D014025:Titanium
chemical_list: D003722:Dental Alloys; C040654:titanium nickelide; D009532:Nickel; D014025:Titanium