Endodontic complications of root canal therapy performed by dental students with stainless-steel K-files and nickel-titanium hand files

By Pettiette MT, Metzger Z, Phillips C, Trope M

Date: 01/1999
Journal: JOE


  • Purpose: to compare the potential of NiTi 0.02 taper hand files (NiTi files) to decrease the amount of straightening of canals and procedural mishaps in the predoctoral clinic, compared with traditional stainless-steel hand 0.02 taper K-files
  • N= 60 maxillary &mandibular 1st and 2nd molars assigned for endodontic treatment to undergraduate senior students with no prior experience in molar root canal treatment. Each student treated one tooth with SS K-files and one molar with NiTi files .


  • Pre-op RG taken for each patient using SCP positioning device and bite block for easier reproducibility of the radiographs.
  • All canals were instrumented with step-back technique and obturated with lateral compaction.
  • Infected canals – intracanal CaOH between appointments
  • Pre-operative radiographs were converted to digital images and stored. Three reference points for each pre-op image was determine for allowing superimposition of post-op tracings from one RG to another.
  • Roots were grouped according to curvature severity
  • The degree of straightening of the apical part of the canals, other procedural errors were evaluated.

Most highlighted Results:

1.Pre-oprative angulations for the SS K-files was 28.62 ° andfor  NiTi files was 28.05 °. Mean postoperative angulation for the SS K-files, was 14.18° and for the NiTi files 25.70°. The difference between changes for the SS K-file vs NiTi files was 10.05°, which was statistically significant.

2.No occurrence of separated instruments neither for SS or NiTi groups but 3 strip-perforations in the SS group were recorded.

3.Instrumentation of highly curved canals with SS K-files resulted in high level straightening for severely curved canals compared to medium and slightly curved canals.

4.Instrumentation of highly curved canals with NiTi hand files significantly reduced the average amount of straightening.

Clinical Significance:

The original curvature of the canal was better maintained with NiTi files, average straightening for NiTi files was consistent in comparison to SS files

Strength: Measures for reproducibility of RG

Weakness: Study tested technical quality based on 2-D radiograph