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Endodontic instruments after torsional failure: nanoindentation test.
Ahmed Jamleh1, Alireza Sadr, Naoyuki Nomura
1Department of Endodontics, College of Dentistry, King Saud bin Abdulaziz University for Health Sciences, National Guard Health Affairs, Riyadh, Saudi Arabia.
Scanning
|March 11, 2014
Summary
Torsional loading significantly reduces the hardness and elastic modulus of endodontic instruments, particularly near the fracture edge. This impacts the mechanical properties of both stainless steel and ProFile instruments after fracture.
Area of Science:
- Materials Science
- Biomaterials Engineering
- Dental Materials
Background:
- Endodontic instruments are prone to fracture during root canal treatment.
- Torsional failure is a common mode of instrument fracture.
- Understanding the mechanical properties of fractured instruments is crucial for improving instrument design and clinical outcomes.
Purpose of the Study:
- To evaluate the effects of torsional loading on the mechanical properties (hardness and elastic modulus) of endodontic instruments.
- To compare the mechanical properties of torsion-fractured instruments with new instruments.
- To investigate localized changes in mechanical properties adjacent to the fracture site.
Main Methods:
- ProFile (PF) and stainless steel (SS) endodontic instruments were subjected to torsional testing until fracture.
- Nanoindentation was performed adjacent to the fracture edge and on the shank of both fractured and new instruments.
- Hardness and elastic modulus were measured using a 100-mN force at 100 locations per region.
Main Results:
- Both PF and SS instruments failed under torsional load, with specific rotation degrees and torque values reported.
- Significant differences in hardness and elastic modulus were observed between torsion-fractured and new SS instruments.
- In PF instruments, the edge region after torsional fracture showed significantly lower hardness and elastic modulus compared to new instruments.
Conclusions:
- Torsional loading significantly reduces the local hardness and elastic modulus of endodontic instruments near the fracture edge.
- These findings highlight the material property changes induced by torsional stress, impacting instrument integrity.
- The study provides valuable insights into the mechanical behavior of endodontic instruments under torsional forces, informing future material development and clinical practices.
