Stress analysis of human tooth root using various root canal instruments

Area of Science:

• Endodontics
• Biomaterials Science
• Dental Mechanics

Background:

• Root canal instrumentation aims to clean and shape the root canal system.
• External root stress during instrumentation can potentially lead to root fractures.
• Nickel-titanium (NiTi) instruments are widely used for their flexibility and efficiency.

Purpose of the Study:

• To compare the external root stresses generated by motor-driven nickel-titanium instruments versus traditional hand files.
• To evaluate the stress distribution within the dentin during root canal instrumentation using photoelastic analysis.

Main Methods:

• Twelve curved mesial roots of first molars were embedded in photoelastic material (PLM-9).
• External root stresses were measured using photoelastic fringe patterns during instrumentation with various motor-driven NiTi instruments and hand files.
• Stress changes were quantified based on fringe patterns, with a complete 60 psi fringe change considered a significant threshold.

Main Results:

• All tested instrumentation techniques produced minimal external root stress patterns.
• Motor-driven nickel-titanium instruments generated comparable or lower stress levels than hand files.
• Light-speed instrumentation technique resulted in the lowest observed stress change in the photoelastic material.

Conclusions:

• Motor-driven NiTi rotary instruments appear to generate minimal external root stress, potentially reducing the risk of root fracture.
• The choice of instrumentation technique, particularly light-speed, may influence the magnitude of stress transmitted through the dentin.
• Further research is warranted to correlate photoelastic findings with clinical outcomes in endodontic treatment.