title: A comparative evaluation of two rotary Ni-Ti instruments in the removal of gutta-percha during retreatment.
abstract: OBJECTIVE
  The purpose of this study is to achieve an effective method to remove root canal filling material from the root canal system. The study, thus, aims to evaluate the efficacy of the cleaning ability of two different rotary Ni-Ti systems; ProTaper Retreatment files and RaCe System compared to hand instrumentation with Hedstrom files for the removal of gutta-percha during retreatment.
  
  
  METHODS
  Thirty mandibular premolars with one single straight canal were decoronated and instrumented with ProTaper files and filled with thermoplastic gutta-percha. After 30 days, the samples were divided into three groups and gutta-percha was removed with the test instruments. The postoperative radiographs were evaluated with known criteria by dividing the root into cervical third, middle third, and apical third. The results were tabulated and Statistical Package for Social Sciences Software (IBM Corporation) was used for analysis.
  
  
  RESULTS
  The mean deviation of the results were first calculated and then t-test and analysis of variance test (two-tailed P value) were evaluated for establishing significant differences. The rotary instruments were effective in removing the gutta-percha from the canals. Therefore, significant difference was observed between the efficacies of the two rotary systems used. The rotary instruments showed effective gutta-percha removal in the cervical and middle one third. (P > 0.05). However, apical debridement was effective with Hedstrom files.
  
  
  CONCLUSIONS
  The study concluded the use of both rotary and hand instrumentation for effective removal of gutta-percha for retreatment.
authors.affiliation: Department of Conservative Dentistry and Endodontics, Madha Dental College, Chennai, Tamil Nadu, India.
authors.forename: C S
authors.initials: CS
authors.lastname: Preetam
authors.affiliation: Department of Conservative Dentistry and Endodontics, G. Pulla Reddy Dental College, Kurnool, India.
authors.forename: M
authors.initials: M
authors.lastname: Chandrashekhar
authors.affiliation: Department of Conservative Dentistry and Endodontics, Narayana Dental College, Nellore, Andhra Pradesh, India.
authors.forename: T
authors.initials: T
authors.lastname: Gunaranjan
authors.affiliation: Department of Conservative Dentistry and Endodontics, Adithya Dental College, Beed, Maharashtra, India.
authors.forename: S Kishore
authors.initials: SK
authors.lastname: Kumar
authors.affiliation: Department of Conservative Dentistry and Endodontics, Madha Dental College, Chennai, Tamil Nadu, India.
authors.forename: S A
authors.initials: SA
authors.lastname: Miskeen Sahib
authors.affiliation: Department of Conservative Dentistry and Endodontics, Madha Dental College, Chennai, Tamil Nadu, India.
authors.forename: M Senthil
authors.initials: MS
authors.lastname: Kumar
keywords: Gutta-percha removal; Hedstrom files; ProTaper Retreatment system; RaCe Rotary System; retreatment procedure