Limiting Torsional Stress on Endodontic Files: Lubrication, Irrigation and/or Technique

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I was recently asked if irrigation and lubrication influenced the stresses a file undergoes during instrumentation. Research that I carried out indicated irrigation and lubrication can reduce torque requirements by as much as 400% compared to rotating in a dry canal. However, one can see from the included chart that the amount of the file’s engagement can be as important as the lubricant itself in reducing torsional stress. Shorter strokes of insertion is more effective in reducing torsional stress than carrying the rotating file to greater depth into the canal with fewer insertions. When the rotating file becomes engaged for more than a very few millimeters, the interface of irrigation is reduced between the surface of the canal and the file and torsional stress increases.

 

The importance of engagement is illustrated. Quantec files were inserted in 1mm increments at 1mm/s with a depth of 8, 10, and 12mm. The torque recorder is an average of 6 files taken for each depth. Note minimum engagement can have approximately the same benefit as irrigation in reducing torque.