Biomechanical (16)

Micro cracks sign 200hThe articles in this section examine the mechanical properties of the SAF, as well as the stress that it inflicts onto the dentin while it scrubs the canal walls, and provide valuable information about the SAF's biomechanical properties.

In a few of the articles, in which the SAF was not portrayed as the preferred choice for treatment, a “ReDent’s note” was added, to suggest how working with the system according to the manufacturer’s directions could help achieve better results.

 

  1. Additional Info

    • ReDent Nova’s note

      Despite the favorable results for the Self-Adjusting File, please note that micro-CT studies of dentinal micro-cracks are unreliable. The lengthy scanning process in a dry vacuumed environment is suspected to cause dehydration and cracking of the teeth, so that the results of such studies are more related to the level of scanning resolution than an actual indication of whether any of the instruments cause dentinal micro-cracks or not.

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  2. Additional Info

    • ReDent Nova’s note

      The main issue with this research is that micro-CT is not a good method to examine the creation of micro-cracks, since the method of examination itself, that involves drying of the roots during the lengthy scanning process, is likely to cause micro-cracks. This explains why the initial scans already present micro-cracks.

      Unsurprisingly, the Self-Adjusting File was found not to create microcracks. More surprisingly, the other instruments (Reciproc, BioRace, TRUShape) did not create microcracks either. 

      Reading the article clarifies that the authors made an effort to avoid the creation of microcracks, by choosing roots that were already cracked (an issue that reduces the chance for creation of new micro-cracks), and by using the smallest possible instruments of each brand, up to size #25. 

      Something else to notice are the micro-CT scans in this article, that reveal the keyhole preparations made by the rotary instruments (all other than the SAF) - excessive removal of sound dentin on one side, and significant uninstrumented parts on the other.

    • publisher publisher
    • View abstract on PubMed. PMID 28216274
  3. Additional Info

    • ReDent Nova’s note

      Several months after the publication, the article was retracted by the authors, due to issues in the SEM procedure that might cause the results to be inaccurate. This does not contradict the fact that the Self-Adjusting File was shown in this research to create less micro-cracks than Mtwo and ProTaper Next, with or without the deflection caused by the examination procedure.

    • publisher publisher
    • View abstract on PubMed. PMID 26599835
  4. Additional Info

    • ReDent Nova’s note

       

      This experiment was designed to test splitting of the teeth by acute occlusal force, which should not be mixed up with vertical root fracture (VRF).

       

      VRFs are fractures originating in the root that have been shown to be associated with propagation of micro-cracks in the radicular dentin. Such micro-cracks were shown to be caused by rotary instruments such as ProTaper.

       

    • publisher publisher
    • View abstract on PubMed. PMID 24666910
  5. Additional Info

    • publisher publisher
    • View abstract on PubMed. PMID 24238449
  6. Additional Info

    • publisher publisher
    • View abstract on PubMed. PMID 23442046
  7. Additional Info

    • publisher publisher
    • View abstract on PubMed. PMID 23321242
  8. Additional Info

    • ReDent Nova’s note

       

      The simulated curved metal canals in this study were larger than the SAF in its relaxed form. In such case the clutch mechanism of the RDT handpiece head is not activated and cannot stop the SAF from rotating in the canal, thus leading to mechanical damage.

       

      This model, which has been used with rotary files, is irrelevant to the SAF, which should never rotate in the canal. These results confirm the manufacturer's instructions of never allowing the SAF to rotate in the canal.

       

    • publisher publisher
    • View abstract on PubMed. PMID 21778091
  9. Additional Info

    • publisher publisher
    • View abstract on PubMed. PMID 20307745