Advancing Endodontic Principles In The Simplest Way Possible

Given rotary NiTi’s dominance today here are some questions regarding their use. If as their advocates state rotary NiTi is a superior instrumentation system why is there so much research on the following:

. The causes of instrument separation

. If, when, why and how to attempt the removal of separated instruments

. The inadequate debridement of oval canals and thin isthmuses, exacerbated in recent years by more conservative preparations

. The production of dentinal micro-cracks after rotary instrumentation

. The need for single-usage

. The requirement of a well-prepared glide path

. The excessive removal of coronal dentin

. The apical extrusion of debris

The results of the research point to consequences that have either correlated with lower success rates or at a minimum not considered indications of positive outcomes. Those advocating rotary NiTi in a balanced way recognize its shortcomings, suggesting precautions and limitations on their use. Those more adamant about their usage either ignore or underplay their downsides strongly defending rotary instrumentation against all other approaches. The more an advocate defends one system against another, regardless of the systems being compared, the more he/she is obligated to support their position with unbiased evidence. To date, declaring the former position without the latter is undisciplined advocacy suggesting indoctrination rather than education.

Repetition of a message in itself does not denote truth or falsehood. It is only by subjecting any message to critical thinking that one can take a stab at finding its truth or falsehood. Condemning the repetition of truths is a form of negative indoctrination that opposes critical thinking. From a practical point of view an individual such as myself repeating statements of which there is considerable support data, but not part of the highly financially enriched dialogue generated by an international marketing strategy encompassing the entire spectrum of education and media outlets, is a speck in the ocean that can only count on even a bit of acceptance if the data transmitted appears to make sense to the relatively few people exposed to it.

That coincidentally my sole voice is met with such consistent condemnation by the critic while ignoring the weaknesses of rotary NiTi that I refer to indicates the corporation’s desire to undermine the messenger, are concerned about the content of the message and to date don’t have an adequate response to the message.

Endodontic instrumentation techniques derive from concepts. The manual use of K-files sounded like a good idea because the predominantly horizontal flutes on a K-files would first engage the dentin with a short clockwise arc of motion with the engaged dentin shaved away with the vertical pull stroke, the twist and pull stroke we all became accustomed to; also referred to as watch winding coupled to an in and out stroke. Yes, there was some degree of distortion in curved canals and an occasional loss of length as the horizontal flutes on the file tended to impact debris apically as the push stroke was employed. That undesirable trait could have been reduced if the instruments had been designed as reamers, but at the time 75 or so years ago all the instruments were fabricated from carbon steel, a material that is vulnerable to separation due to its poor resistance to torsional stresses.

Consequently, the idea of using reamers, instruments that shave dentin away with the horizontal arc of motion were recognized as designs and utilization that would lead to a greater incidence of instrument separation. That should have all changed with the introduction of stainless steel that did away with the weaknesses of carbon steel. But, it didn’t simply because of the stagnation of the educational institutions. While separation was not a big issue in using K-files, their use being the dominant method of instrumentation prior to the introduction of rotary NiTi, subjects the dentist to hand fatigue, distortions of curved canals and loss of length.

This situation left a lot of room for improvement if ways to overcome these shortcomings could be found. We are all familiar with the introduction of rotary NiTi. It reduced hand fatigue, canal distortions, procedural time requirements and in itself would not impact debris in such a way that it would lead to loss of length. Because of these improvements it was hailed as a paradigm advancement.

With its wider usage, shortcomings that were not generally associated with the manual use of K-files were identified including a higher incidence of instrument separation, inadequate debridement of oval canals and thin isthmuses, the need for single usage and the production of dentinal micro-cracks in the canal walls. Just like the manual use of K-files that left a lot of room for improvement, these shortcomings of rotary NiTi in their turn left room for improvement. Who wouldn’t want to eliminate instrument separation, inadequate three-dimensional debridement and single usage that makes the technique so expensive?

That is where 30o oscillations of stainless steel relieved reamers come in. They are far more efficient than K-files at negotiating the length of the canal without impacting debris. Hand fatigue is eliminated for the most part because right from the beginning the instruments are engine-driven. They are immune to breakage due to their implementation with short 30o arcs of motion. At a frequency of 3000-4000 cycles per minute instrumentation with each instrument is rapid enhanced by the sonic activation of the irrigates further improving the debridement process. Just as rotary solved the shortcomings of the manual use of K-files, 30o oscillating stainless steel relieved reamers have solved the problems most specifically of rotary NiTi, but also those associated with the manual use of K-files, most importantly without introducing any new problems.

There is no magic here. The benefits derived from 30o oscillations of stainless steel relieved twisted reamers exist because they operate within the mechanical properties of the materials. Instruments negotiating even highly curved canals will not break if limited to short arcs of motion. Nor will stainless steel designed as relieved reamers distort canals if confined to short arcs of motion. The instruments are simply acting in accordance within the environment they are operating. Dentin offers more resistance to deformation than the tip of the instruments when confined to short arcs of motion. Consequently, it is the instruments that conform to the canal anatomy. Stainless steel reamers if not confined to short arcs of motion would cause the canals to conform to the instruments which is the reason they are not used in this manner.

Once one has the insight to see these inherent advantages it becomes totally explicable why they overcome all the downsides of both rotary NiTi instrumentation as well as the manual use of K-files. Its also becomes obvious why at least one advocate of rotary wishes to obscure these advantages and undermine anyone who speaks positively about alternative methods. We should all keep in mind that more important than the final decision on what to use is the process of critical thinking, the best tool available to determine what we should be using. That is far more likely to put us on the right track regarding any decisions we make. Most importantly, given the overall pugnacious temperament marinating our environment today, we should be most aware of any comments that employ encouraging an emotional response claiming the approval of a vast hypothetical majority with one’s personal views. Such statements as “everybody knows” or “its obvious to everyone” are appeals to join a tribe without explaining in detail the merits of that tribe. In short, they are psychological tools to create a reaction based on emotion, a necessity when what one wants others to believe is not substantiated by existing evidence or is challenged by conflicting data.

Off course it is highly possible that this post will be criticized by the critic and that is fine. I simply want such criticism to be based on solid evidence. And so it goes.

Regards, Barry