INSTRUMENT SEPARATION : NEVER ENDING DILEMMA IN ENDODONTICS
“Will the prognosis of the tooth be affected if we leave a separated instrument inside the canal?
It’s a very frequently asked question. The separation of an instrument brings about nightmares to the clinician as well as the patient. The success of the treatment outcome is compromised when an instrument is separated during the shaping and cleaning procedures. A literature review revealed the prevalence of retained fractured instruments in between 0.7 and 7.4% of teeth undergoing root canal treatment. It can happen even to experienced clinicians following the most appropriate preventive measures. Instrument fracture may occur in both anterior and posterior teeth, but it is most frequently reported in molars with a higher incidence in the Mesio Bucaal root, predominantly in the apical third. It is not the fractured instrument segment that causes failure of endodontic treatment, but the inability of the operator to clean the canals apical to the separated instrument. The most common etiologic factors that contribute to the instrument separation are attributed to operator-related errors such as improper use of instruments, applying too much pressure on the rotary instruments, overuse of instruments as well as complex anatomical variations in the root canal system.
Modern rotary endodontic files are made up of nickel-titanium. The added benefit of NiTi is its flexibility, and resistance to fracture as well as shape memory. On the other hand, when a NiTi file breaks, it separates without informing the operator. The metallurgy of the rotary NiTi files has been evolved over a period of time. The new generation heat-treated files have controlled memory as compared to the shape memory of normal NiTi files. These alloys, when heat treated, undergo a crystalline transformation phase from austenite to martensite phase. This gives them the property of Super-elasticity. Their resistance to fracture increases by ten folds. Despite the advances in the rotary systems, the operator must take utmost care to avoid any unavoidable circumstances.
The following things must be kept in mind to avoid instrument separation:
1. Manual files should be discarded if there is any sign of opening up of flutes or kinks.
2.Follow the Manufacturer’s recommended torque values for rotary files so that instrument rotate and cut without exceeding its own plastic deformation (Fracture limit)
3.Minimize the number of users of rotary files, Inspect the rotary instrument after each use. Any sign of unwinding of flutes or shiny areas is an indication to discard the instrument.
4.Endomotor with a wide range of speed and torque parameters offer greater control for a diverse brand of files. Reciprocation movement is an added feature that can help to reduce torsional stress on the rotary instruments.
5)Avoid forcing the rotary instrument inside the canal. Recapitulation and sequential enlargement remarkably reduce stress on the file.
AUTHOR
-Dr. Harsh Amlani.