Mechanized Ni-Ti Rotary Endodontics What Goes Around, Comes Around
Note: This article was originally published 20 years ago and discussed techniques being taught at the time – circa 2003 . I have edited the article (with teal colored text) to reflect what I am doing today – in 2021.
Mechanized Ni-Ti Instrumentation has taken Endodontics by storm. What is unusual about the rapid acceptance of this method of instrumentation is how most manufacturers and lecturers minimize the need to have a #15 file at working length before moving to this type of instrumentation. This is laughable. Virtually all instruction literature first states “Obtain a working length with a size #15 file.” Then move to the mechanized Ni-Ti Engine files.
Ask any Endodontist and they will tell you that the most difficult part of treatment is the location, and negotiation of small calcified or tortuous canals. It is not doing the bodywork of the canal. (Shaping the body may be the most “tedious” part of treatment but it certainly is not the most difficult.) Achieving apical patency in difficult canals can only be accomplished through the use of small hand instruments that allow transmission of the minute subtleties of canal system anatomy to the clinician. This “Endodontic Touch” is the essence of skilled endodontic treatment since these tiny probing file manipulations are the “eyes” of the clinician. Once the working length has been established with a size #15 file, the method used in shaping the body of a canal is really not that important, whether it is with hand files, reamers, rotary or sonic/ultrasonic instruments.
What HAS become generally recognized is that rotary motion is the most efficient way of shaping and enlarging the body of the canal; hence the popularity of rotary instruments, at the expense of the old “push pull step back filing” 1980s method. Oliet et al noted the efficiency of rotary instrumentation for canal enlargement as far back as 1970s. The advancements in Ni-Ti metallurgy have allowed for the creation of more flexible (albeit expensive) instruments. Unfortunately, pure rotary instrumentation does little to address the problems of irregularly shaped canals, canals with an isthmus and those canals with fins. These can only be cleaned with the use of irrigation and hand files used in a deliberate effort to clean these areas.
Attempting to “encompass” these areas with the rotary files would cause excessive enlargement and weakening, thinning or stripping of the root dentin. As much as we would all love a device (sonic/ultrasonic/rotary/laser/suction etc) that you could turn on and walk away from, negotiation and filing of irregularly shaped canals is still required.
(It remains to be seen whether “newer technologies” such as GentleWave, which claim to be able to do this, are as efficient as they claim. Unbiased, peer reviewed, non industry sponsored research is required for us to very these claims- Editor 2021)
The pitches of clinicians selling instruments of their own design must be examined. When claims of 75% reduction in treatment time are made, they must be scrutinized closely. In the real world of Endodontics, history has shown that most “time saving” devices/techniques are rarely supported with good results. When they fail, they often fail in the worst possible way, resulting in the need for protracted treatment times.
Ni-Ti rotary instrumentation is best used for shaping of the body of the canal after the initial working length and apical patency has been established. Attempting to use these instruments for “path finding” or “canal negotiating” can result in catastrophic instrument breakage, usually at the most complicated part of the canal. (junction of joined canals, sharp bends, dilacerations and apical deltas). (When this was written, heat treatment and ultraflexible files had not yet been invented and sold. Today, more flexible instruments (Pathfinders, for example) allow for instruments to reach the apex more easily and less need for “body work”. Also, there is more emphasis on conservation of dentin and decreased taper – “skinnier preps”. ) These fractured instruments can sometimes be removed or bypassed but at great cost in time and effort. (translated… $$$) In the worst-case scenario, when a fractured file is used in a “crown-down” fashion, a necrotic apical portion of the canal is left completely untouched. This virtually guarantees failure of the case or the need for surgical resection of the inaccessible portion.
The basic principles of Endodontics must always be adhered to:
(1) Establish a reliable working length (Electronically and/or via radiographic images)
(2) Maintain apical patency through recapitulation with smaller hand files
(3) Establish good canal taper to allow for better irrigation and obturation of the deeper apical portions of the canals
(4) Take a cbCT image BEFORE and DURING treatment if there is any question about the canal system anatomy. Maintain a “mental map” of the canal system in your head through the use of sensitive files and constant subtle tactile feedback.
(5) In Endodontics the axiom of “better, easier, cheaper…pick two” is the rule.
There is no magic bullet. Do not be fooled by those who wish to sell you an expensive chrome-plated revolver.