What Does Common Sense In Endodontics Mean?

As in all aspects of life, common sense is based as much as one can muster, on a pragmatic intuitive decision-making process. If counterintuitive conclusions are reached, common sense then requires deeper thought processes to explain the deviation from what would appear to be rational thinking. In the case of endodontics the application of common sense requires a familiarity with the research, broad clinical experience and an understanding of the stresses that the instruments and teeth both impart and receive under function. Making judgments on the superiority of one system over another, using the above criteria, is an incremental affair with individuals making overall assessments that will vary depending upon the weight given to the pluses and minuses of each system.?

Take rotary NiTi instrumentation as an example. It does not exist in a vacuum. It’s introduction was based on the perceived shortcomings of the manual use of K-files. It is a well-established fact that the manual instrumentation of curved canals can be a fatiguing and time-consuming process. Common sense guided the development of rotary endodontics to reduce hand fatigue and the time needed for canal instrumentation. The greater flexibility of NiTi made it adaptable to shaping curved canals using a rotary engine, something stainless steel was incapable of without causing distortions. By implementing rotary NiTi instruments for the bulk of canal instrumentation hand fatigue was significantly reduced as the time requirements for the procedure. Based on these advantages, it made common sense to employ this newer method of instrumentation.

With usage, it quickly became apparent that rotary NiTi instrumentation was vulnerable to separation. The advantages of its use now had to be weighed against the increased possibility of instrument breakage. To reduce the incidence of separation required exercising several forms of precautions including staying centered that compromised the three-dimensional cleansing of oval canals, greater enlargement of the glidepath using conventional manual K-files and more conservative rotary preparations, the first compromising canal debridement and the last two narrowing the gap between what the traditional techniques had done and the final result produced by rotary NiTi. Even in its modified form, rotary generally still reduced both hand fatigue and procedural time requirements, features that most dentists found desirable.

While vulnerability to separations dampened rotary NiTi’s allure, many dentists believed that the only alternative to employing rotary was to rely on the manual use of K-files, a traditional method of instrumentation that made endodontics so wearying. Weighing hand fatigue and excessive time requirements against less hand fatigue and shorter time requirements trumped the increased risk of instrument separation for many dentists. The advocates of rotary were at the same time also emphasizing the reduced possibility of separations if the proper precautions were followed including single usage, proper glide path creation, centered shaping, crown-down preparations, short light pecking motions, and more conservative shaping. The propensity to avoid hand fatigue as much as possible while speeding up the instrumentation process now bolstered by a series of effective precautions??encouraged the use of rotary NiTi despite its vulnerabilities. After all, most dentists believed the only alternative was the manual use of K-files. Given the limited choices that dentists believed were available, it made common sense to adopt and employ rotary endodontics and so it remains for the most part to this day.

What has changed that would stimulate the exercise of common sense in determining what works best? Consider 30o arcs of motion powered by a handpiece oscillating at 3000-4000 cycles per minute employing unrelieved twisted reamers through a 10/02 and relieved twisted reamers from 15/02 onwards through a 40/02. What benefits do these tools bring to the instrumentation process? Being engine-driven we now have a means of dealing with hand fatigue. In fact, unlike rotary that still requires the manual creation of a glide path, the entire shaping process from start to finish can be accomplished using the 30o oscillating reamers. The dentists now have a choice in the elimination of hand fatigue. Rotary is not the only alternative and a limited alternative at that.?

Of greater significance, however, is the fact that that stainless steel twisted reamers confined to a 30o arc of motion are virtually invulnerable to breakage. I’ve made this point many times in previous posts, but looked at from the vantage point of common sense, it represents a clear advantage over rotary NiTi. If you want to avoid instrument separation use relieved twisted reamers confined to short arcs of motion, something that rotary NiTi can at best modify without eliminating it. But, the greater flexibility of NiTi surely is an advantage when shaping curved canals and isn’t distortion-free shaping the desired end product of effective instrumentation? Nothing beats the greater flexibility of NiTi especially in its newer heat-treated products. Would not distortion-free shaping still trump other systems for this fact alone??

That would, indeed be the case were it not for the insights gained by Dr. James Roane who described a short arc form of manual instrumentation using stiffer stainless steel K-files that instrumented and shaped curved canals without distortion. Again, I have discussed the non-distorting mechanics of balanced force in previous posts and it is accepted as effective clinically and academically. Rotary advocates might note that balanced force as described by Dr. Roane is a manual process bringing up the original concerns of hand fatigue and excessive time requirements. This is a genuine common sense observation and in its present form the manual application of balanced force would still be logically unacceptable to many dentists.

A dramatic insight is the fact that engine generated 30o oscillations can be applied similarly to the manual balanced force technique doing away with the associated hand fatigue and excessive time requirements. Research papers confirm the fact that motions confined to 30o allow stainless steel to follow canal anatomy without creating ledges and other potential distortions. By using relieved reamers, the instruments are more flexible than the original K-files and are more adaptable to any curves the instrument may encounter on the way to the apex. The application of common sense has now expanded with the recognition that systems presently exist that are immune to breakage, can, therefore, vigorously make contact with all walls evenly in highly oval canals and stay true to the original canal anatomy even though stiffer stainless steel reamers are being employed.?

For common sense to be most effective, we want to include as much data as possible. When the data was limited to the manual use of K-files or rotary NiTi, the application of common sense operates on a very limited wavelength. As more data is added the application of common sense becomes more complex, but despite that complexity it has the potential to reach increasingly valid conclusions. That is the process I see happening as we observe the evolution of endodontic instrumentation.

?One final note: I find it ironic that following years of rotary NiTi innovation, one sequel to their present state of evolution is the introduction of numerous laser powered irrigation systems, units that cost tens of thousands of dollars to power the irrigants to remove the tissue and bacteria that rotary has been shown to leave untouched as the canals become more complex in their pulpal configurations. Rotary instrumentation instituted a major increase in the cost of endodontic armamentarium, a cost that was then far exceeded by the cost of laser irrigation systems. It is here that most profoundly, I believe common sense has gone adrift. These so-called major innovations have yet to prove themselves productive of higher success rates. What they have done is enrich the coffers of the companies producing them aided by their advocates that emphasize the advantages of “newness” without offering data associating any of these techniques with improved clinical results. Exercising common sense also takes practice.

Regards, Barry?

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