title: A comparison of the relative efficacies of four hand and rotary instrumentation techniques during endodontic retreatment.
abstract: OBJECTIVE
  The purpose of this study was to quantify the amount of remaining gutta-percha/scaler on the walls of root canals when two engine-driven instruments (Quantec and ProFile) and two hand instruments (K-file and Hedström file) were used to remove these materials. The amount of apically extruded debris and the time required for treatment were also recorded.
  
  
  METHODS
  One hundred extracted mandibular premolars were prepared using a modified step-back, flare technique and obturated with the lateral condensation technique. After repreparation with the test instruments, the specimens were cut transversally at the cervical, middle and apical thirds with steel discs and the three sections were split longitudinally. The amount of residual debris on the canal walls in each section was examined using a stereomicroscope.
  
  
  RESULTS
  In all groups the cervical and middle thirds showed no debris. In the apical third, obturating material was observed in some specimens. No statistically significant difference was found between the two groups for incidence of debris, although the Hedström group showed a greater number of samples with remaining gutta-percha/sealer. When analysing dirty specimens only, there was a statistically significant difference between the four groups (P < 0.01) with the Hedström group having significantly less length of canal wall with remaining obturation material than the Quantec group. There was no significant difference amongst the groups for weight of extruded debris. However, there was a significant difference amongst the groups for mean treatment time with the Hedström file group requiring significantly less time than the Quantec group (P < 0.001); no significant differences were found between the other groups. Six instruments fractured in the Quantec group, four in the ProFile group, two in the Hedström group and two in the K-type group.
  
  
  CONCLUSIONS
  The results showed that overall, all instruments may leave filling material inside the root canal. During retreatment there is a risk of instrument breakage, especially rotary instruments.
authors: Department of Endodontics, Osaka Dental University, Osaka, Japan.
authors: N
authors: N
authors: Imura
authors: A S
authors: AS
authors: Kato
authors: G I
authors: GI
authors: Hata
authors: M
authors: M
authors: Uemura
authors: T
authors: T
authors: Toda
authors: F
authors: F
authors: Weine
mesh_terms: D000704:Analysis of Variance; D001641:Bicuspid; D003786:Dental Pulp Cavity / Q000648:ultrastructure; D004867:Equipment Design; D004868:Equipment Failure; D006171:Gutta-Percha / Q000737:chemistry; D006801:Humans; D019233:Retreatment; D012387:Root Canal Filling Materials / Q000737:chemistry; D018915:Root Canal Preparation / Q000295:instrumentation* / Q000379:methods; D012390:Root Canal Therapy; D012399:Rotation; D013223:Statistics as Topic; D013499:Surface Properties; D013997:Time Factors; D019227:Tooth Apex / Q000648:ultrastructure; D019237:Tooth Cervix / Q000648:ultrastructure
chemical_list: D012387:Root Canal Filling Materials; D006171:Gutta-Percha