Canal markings produced by endosonic instruments

Abstract

It has been recognised that ultrasonic files leave a diagonal pattern within the canal following endosonic instrumentation. There is confusion on the causative factor on the production of these marks. Furthermore there is little information about the marks produced by sonic files. An in vitro system consisting of highly polished dentin discs demonstrated that the ultrasonic K-file made a diagonal pattern that was an imprint of the cutting edges of the file. The sonic files produced different markings which were the result of their longitudinal and transverse motion. Root canals of extracted teeth were prepared with these instruments and similar grooves were observed. The ultrasonic K-file had diagonal grooves in the coronal and middle third of the root canal but longitudinal marks in the apical third. The rispisonic and shaper files produced debris even in the presence of NaOCl. This debris was formed into discrete parallel bands. Both longitudinal and transverse grooves were present and the canal had many other scratches similar to those seen with the dentin discs. There were differences between the marks produced by either ultrasonic or sonic endosonic instruments but it is unknown whether this influences the long term prognosis of the root canal therapy.

Review of Contemporary Irrigant Agitation Techniques and Devices

“…In addition, it is difficult to control the cutting of dentin during UI and hence the shape of the prepared root canal. Strip perforations as well as highly irregular-shaped canals were frequently produced (128,146). Therefore, UI is not generally perceived as an alternative to conventional hand instrumentation (101,125,139,147).…”

The principles of techniques for cleaning root canals

“…A freely oscillating instrument will cause more ultrasound effects in the irrigating solution than a file that binds in the root canal. 125 Furthermore, use of ultrasonic files during canal preparation may lead to gouging of the root canal walls 126 and severe transportation of the canal with zipping and strip perforations. 127 Several clinical studies have reported greater canal and isthmus cleanliness in the apical region of the root canal when passive ultrasonic activation has been used following canal preparation.…”

Comparison of Debris Removal with Three Different Irrigation Techniques

“…Because agitation of irrigants has been shown to increase irrigation effectiveness (13), various manual agitation techniques and machine-assisted agitation devices have been developed (14). Continuous ultrasonic irrigation has been shown to produce cleaner canals and isthmuses (15)(16)(17); however, ultrasonic irrigation must be used with care because procedural accidents (canal transportation, zipping, perforation) and creating an irregularly shaped canal preparation are possible, especially in curved canals (18)(19)(20). Another aspect of irrigation effectiveness is volume.…”