Preponderance of Evidence That Rotary NiTi Causes A Host of Problems

A casual scanning of the endodontics literature provides overwhelming data that rotary NiTi causes instrument separations, dentinal micro-cracks, inadequate debridement of oval canals, produces a smear layer that clogs the dentinal tubules and even produces distortions. Many of these are comparative studies where corporate sponsorship comes into play. In short, rotary NiTi manufacturers are competing against themselves. That same process is applied when directed against the 30o oscillating stainless steel reamers.

A google investigation on corporate influence in dental research shows it is very much in play. Given this environment, the best way to render accurate assessments is hands-on experience. In that regard, we have to assume that tools we use to render our judgments, mainly referring to 3D printed teeth, are reflective of what we are learning. In that case, 3D printed teeth are not ideal, but we are mandated by OSHA to use them. Due to their limitations, I must provide a detailed discussion on how to interpret the results attained and contrast that with my clinical experience on natural teeth.

The goal is to provide the dentist with the safest, most effective and efficient means to shape and cleanse the canals, safety being applied to both the instruments and the teeth being treated. If one denies that rotary produces dentinal micro-cracks, one has to negate the monumental amount of data that says that it does. In doing that, one has to also deny the implications of Newton’s Third Law of Motion. The majority of these studies have also concluded that systems limited to short arcs or motion are the least likely to introduce dentinal micro-cracks. There is a strong correlation between those systems that are most prone to fracture and the ones that produce the greatest number of micro-cracks. All of this must be denied to believe that rotary NiTi does not produce micro-cracks. This consistent relationship is brought to our attention because instrument separation is so obviously observable with a separation rate ranging from 2% to 8% making it a significant form of failure.

Greater tapered rotary NiTi instruments take away more tooth structure than needed from the mesial and distal walls. That occurs simply because the canals often oval in cross-section are thinner in that dimension than they are in the bucco-lingual plane. It has been documented that a portion of the dentin removed mesially and distally is deposited in the wider bucco-lingual plane acting as a barrier to effective irrigation in that plane. Given that the rotary instruments are not applied aggressively in that plane, the impaction of debris bucco-lingually compromises three-dimensional debridement. This phenomenon has been documented and there is no getting around it as long as the options available are limited to rotary NiTi forms of instrumentation.

The key to improved instrumentation is always the same, employing a system that is invulnerable to breakage. Such a system can the be applied to all canal walls. Starting with the thinnest stainless steel reamers, they are more capable of negotiating the canal space mesio-distally, but also bucco-lingually removing dentinal debris rather than impacting it bucco-lingually. Such a thorough process is defined as internal routing, a three-dimensional application of the instruments against all the canal walls logically resulting in superior debridement, something that is confirmed by the instrumentation of transparent 3D printed teeth with complex pulpal anatomy. All accomplished with high frequency short arcs of motion, the instruments remain intact and in accordance with Newton’s Third Law of Motion the production of micro-cracks is kept to a minimum. These are two positive observations, no instrument separations and a dramatically reduced production of micro-cracks. Additionally, eliminating the smear layer is another aspect of 30o oscillating stainless steel reamers.

What some rotary NiTi advocates are saying is that instrument separation should not be the determining factor in what to use. They support that contention by claiming falsely that all instrumentation systems break. That is a denial of the singular most important contribution that the 30o oscillation of stainless steel relieved reamers have over rotary NiTi. There is also a deemphasis in evaluating instrumentation effectiveness by ignoring any studies that conclude bucco-lingual debridement less than adequate when instrumenting oval canals. If the final results look good in the mesiao-distal plane, what is observable on a periapical x-ray, it is considered sufficient proof of effectiveness. For a more thorough means of system evaluation, we should be including the implications of these studies of the various systems. However, once the third dimension is dismissed as a factor in evaluating a system, thinner mesio-distal rotary NiTi preparations further compromise the bucco-lingual preparation of oval canals, a factor that is no longer part of critically analyzing their function, a convenient retreat from a detailed analysis of what is working most efficiently. To evaluate a system based on its two dimensional appearance on x-ray is an artificially imposed limitation for the sake of marketing a product that has been documented to be weak in cleansing the third dimension.

Like every marketing effort, the manufacturers and their advocates emphasize comparisons that favor their products. The marketing technique requires a denial of any data that challenges the superiority their products. The tactics used in the marketing strategy include selective research studies, criticism of those who challenge their products on both personal and professional grounds, supportive opinion leaders, an army of company reps, special financial deals, dominance in the dental schools and broadly purchased media support. In my particular case, I represent the challenge of a system other than rotary. The concept of 30o oscillations of stainless steel relieved reamer instrumentation challenges the entire concept of rotary NiTi rationally being the dominant system.

Gaining traction in the ideas behind the high frequency 30o oscillations of relieved twisted stainless steel reamers can hurt the entire rotary industry, not just redistribute it among rotary competitors. For that reason it is doubly important to diminish the potential impact of this alternative approach. One does not witness the level of vitriol displayed in my challenges when advocates of different rotary systems debate. Competition between similar systems is evidently far less confrontational than that encountered with a system that negates all rotation and NiTi instrumentation save for the last instrument when that single instrument then encounters minimal resistance. Judging from the level of responses being less than collegial, evidently offering an approach that negates the main characteristics of rotary NiTi instrumentation is viewed as a much greater challenge. I don’t believe that would be the case if the alternative being offered was not so solidly based on sound mechanics and common sense. That this alternative system claims to eliminate the major weaknesses of rotary NiTi, namely, instrument separation, contrasts the oscillating approach with all other rotary systems be they used in a continuous or interrupted manner.

From a viewpoint of human nature, I understand the more personally degrading commentary directed my way. I believe that tolerance and openness to diverse opinion is part of a learned ability that we try to attain as we mature and for the most part that is the case especially among colleagues. As I think about the aggressive commentary, it appears that the goal of being more informative is no longer center stage. Given such discussions on an open platform accessible to a large audience, those intent on “winning” beyond all else will take whatever steps they can conjure to gain the support and favor of those listening and that includes personally degrading the opposition. Given our prehistoric heritage of tribalism the potential of creating an “us” against “them” response is always possible. We should all be aware that this is an appeal that is the very contradiction of critical analysis, the basis of true learning and has no place in any legitimate dialogue.

What boggles my mind is when a critic, also an endodontist, goes on to say without any evidence that I am damaging patients because of my ignorance. Well, according to this particular critic I must have been doing this for well over 50 years. In that time, we built up a very successful practice that could only have come about by satisfied patients and their dentists who sent them to us. I have posted many of my cases on linkedin and have gotten compliments on that work. In the meantime, I am in my 53rd year as a practicing endodontist and believe I am turning out my best work to date. Teaching what I do and is evidently my major offense because it does not emphasize rotary NiTi for the many reasons stated at the beginning of this post. And here we are.

Regards, Barry