title: Comparison of two techniques for assessing the shaping efficacy of repeatedly used nickel-titanium rotary instruments.
abstract: BACKGROUND
  The shaping capacity of nickel-titanium (NiTi) rotary instruments is often assessed by photographic or micro-computed tomography (micro-CT) measurements, and these instruments are often used more than once clinically. This study was conducted to compare photographic and micro-CT measurements and to assess if the repeated use of NiTi instruments affected the shape of canal preparation.
  
  
  METHODS
  Ten new sets of ProTaper Universal instruments (Dentsply-Maillefer, Ballaigues, Switzerland) were used in 60 resin blocks simulating curved root canals. Groups 1 to 6 (n=10) represented the first to sixth use of the instrument, respectively. Digitized images of the prepared blocks were taken in both mesiodistal (MD) and buccolingual (BL) directions and area measurements (mm(2)) were calculated using AutoCAD (Autodesk Inc, San Rafael, CA). The volumes of the same prepared canals were measured using micro-CT (mm(3)). Statistical analysis was performed to detect differences between photographic and volumetric measurements and differences between uses.
  
  
  RESULTS
  Two-way repeated-measures analysis of variance revealed significant differences between groups (P < .001). Regarding measurement type, there were no significant differences between BL and MD measurements, but there were significant differences between micro-CT and BL measurements (P < .001) and micro-CT and MD measurements (P=.001). Significant differences were also noted between uses.
  
  
  CONCLUSIONS
  Within the limitations of the present study, micro-CT scanning is more discriminative of the changes in canal space associated with repeated instrument use than photographic measurements. Canal preparations are significantly smaller after the third use of the same instrument.
authors.affiliation: Department of Endodontics and Restorative Dentistry, University of Siena, Policlinico Le Scotte, Viale Bracci, Siena, Italy. ounsih@gmail.com
authors.forename: Hani F
authors.initials: HF
authors.lastname: Ounsi
authors.forename: Giovanni
authors.initials: G
authors.lastname: Franciosi
authors.forename: Raffaele
authors.initials: R
authors.lastname: Paragliola
authors.forename: Khalid
authors.initials: K
authors.lastname: Al-Hezaimi
authors.forename: Ziad
authors.initials: Z
authors.lastname: Salameh
authors.forename: Franklin R
authors.initials: FR
authors.lastname: Tay
authors.forename: Marco
authors.initials: M
authors.lastname: Ferrari
authors.forename: Simone
authors.initials: S
authors.lastname: Grandini
mesh_terms: D004396:Coloring Agents; D003722:Dental Alloys / Q000737:chemistry*; D003786:Dental Pulp Cavity / Q000033:anatomy & histology*; D004867:Equipment Design; D017743:Equipment Reuse; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007281:Ink; D008422:Materials Testing; D008953:Models, Anatomic; D009532:Nickel / Q000737:chemistry*; D010781:Photography; D018915:Root Canal Preparation / Q000295:instrumentation*; D014025:Titanium / Q000737:chemistry*; D055114:X-Ray Microtomography
chemical_list: D004396:Coloring Agents; D003722:Dental Alloys; C040654:titanium nickelide; D009532:Nickel; D014025:Titanium