Am I biased towards 30o oscillating stainless steel relieved twisted reamers?

Of course the answer is yes. A good follow-up questions would be: What are the motivations for that bias? The answer to that is multifold. The bias starts with an unfavorable opinion regarding the unpredictable tendency for rotary NiTi to separate as canal anatomy becomes more complex. One could call that a negative bias. I wanted to avoid any incidence of instrument separation and was motivated to start thinking about instrumentation procedures that would eliminate that possibility. In the quest to inform myself on the causes of instrument separation I delved into the copious?literature available on this subject. Collaterally, the research was also informative on related topics such as inadequate debridement of oval canals and thin isthmuses, the production of dentinal micro-cracks and the need for rapid replacement of the instruments.

As many of you know who read the posts I write, we came up with a method of instrumentation that substitutes 30o ocscillations for full rotations whether generated continuously or in an interrupted manner (reciprocation). Confined to 30o arcs of motion the stainless steel reamers proved to be virtually invulnerable to breakage with the results published in the Journal of Endodontics in 2009. Considering the fact that separation was the main issue, finding an engine-driven way to preventing them was something I was quite enthused about. You can call that bias, but it was bias based on the positive resolution of a problem that is inherent to rotary NiTi.?

Ok, so we solved that problem, but in and of itself, it means little if in the process of avoiding separation the canals undergo inadequate debridement. That, however did not turn out to be the case. Confined to short arcs of motion that prevent instrument separation, the stainless steel twisted reamers both unrelieved and relieved can be aggressively applied to the canal walls of oval canals as well as the the thin isthmuses and flat anatomy that often exists between canals without any increased danger of separation. The instruments not only remain intact, but used as “internal routers” they are far more capable of contacting all the canal walls removing a more or less uniform amount of dentin circumferentially resulting in canal preparations that reflect the original canal anatomy in larger form. We proved this concept in videos that showed the complete cleansing of the pulpal space of the mesial root of a mandibular molar that not only included the mb and ml canals but the isthmus space common to both canals.

Aware of the literature that documented the inadequate cleansing of oval canals using rotary NiTi instrumentation, being able to perform three-dimensional debridement via 30o oscillations of stainless steel relieved twisted reamers is a major step forward. To further prove the concept of the effective cleansing of oval canals, we instrumented and obturated a number of extracted teeth with oval canals and then sectioned them to see the effectiveness of instrumentation as well as the obturation that followed. The sections, shown in previous posts, displayed excellent?three-dimensional cleansing and obturation and is in stark contrast to the many studies showing inadequate cleansing of oval canals employing rotary NiTi. So, yes in terms of the elimination of breakage and superior debridement I am biased, but with good reason.

Stainless steel instruments are stiffer than NiTi of the same dimensions, a fact that resulted in a number of research papers concluding that stainless steel was far more likely to produce distortions in curved canals. All these studies involved the manual use of K-files where there was little control over the amount of rotation applied to these instruments in the canal. We changed the rules of the game by substituting reamers for files. With fewer more vertically oriented flutes, the reamers are more flexible than comparably sized files and encounter less resistance as they negotiate the length of the canals. By adding a flat along their working length we further enhanced their flexibility and further reducing the resistance encountered within the canals. Most importantly, confined to a high frequency 30o arc of motion the stiffer stainless steel reamers minimize their potential to distort curved canals. The explanation of this phenomenon is based on Dr. James Roane’s balanced force technique, a manual usage of K-files that involves short arcs of motion where under the these unique circumstances the resistance of the canal wall to deformation is greater than the tip of the stainless steel instruments at least through size 60/02. The oscillating handpiece turns the balanced force technique into an engine-driven system that eliminates hand fatigue and greatly reduces the time needed for instrumentation. The best proof that I could offer to confirm the non-distorting ability of the 30o oscillating reamers was to show numerous highly curved cases shaped and obdurated, something I have done repeatedly on LinkedIn.

Over the course of many posts, we have shown evidence that in 30o oscillations the instruments are virtually invulnerable to breakage, are applied three-dimensionally against all the canal walls, do not cause distortions and can be used multiple times simply because they remain intact. Regarding these specific topics, there is no question that I am biased, but I have also shown evidence that they work as described and are answers to problems that have yet to be resolved in the evolution of rotary NiTi to date.

Another topic regarding instrumentation is the extrusion of debris. Here, it is more difficult to claim superiority for any given system. The literature states that all instrumentation systems extrude debris apically with studies often contradicting one another in what produces the most and the least. The one consistent outcome that most studies agree on is the fact that the traditional manual use of K-files produce the most amount of extruded debris. This makes sense given their kinetics that consist of an up and down motions leaning against all the canal walls shaving dentin away on the pull stroke and impacting debris and driving it apically on the push stroke. Files with their predominantly horizontal flute orientation are designed to impact debris on the in stroke. The same file used with balanced force produces a minimum amount of extruded debris. It is the kinetics that matter. Extruded debris is significantly reduced when the K-file is used with a reamer-like action.

The stainless steel relieved twisted reamers are used in a similar manner as the K-files used with balanced force with the added advantages of an even shorter arc of motion than manually applied, reamers that are more effective shaving dentin away from the canal walls when the horizontal arcs of motion are applied consistent with the balanced force technique that keeps the instruments confined to the canal space without inducing distortions. So,yes some debris is extruded, but consistent with the balanced force technique the debris extruded would be far greater if the instruments were being applied with greater arcs of motion.

I can’t end this post without commenting on my critic’s constant theme that I talk about the advantages of the oscillating reamers because they are the products our company produces as if that were some form of sin. Of course, that is true. But, it is equally true that I developed these products for my own endodontic practice, something that I am fully involved with in my 50th year as an endodontist. They have made my life as an endodontist easier, less stressful and far less expensive had I stayed with rotary NiTi from the beginning without questioning their shortcomings. What I find mind numbing is his conclusion that anyone touting their own creative improvements is somehow morally defective. Effective innovations is a potential source of added income, but that does not make the person touting those improvements evil. To use his criteria as a guide would put us back in the dark ages. And I am quite sure he doesn’t really extend that thought process beyond his narrow goal of disparaging me and what I say as a way to limit any negatives associated with rotary NiTi. If the reasoning I employ in being both critical of rotary NiTi and positive regarding the solutions oscillating reamers provide were off base and ineffective he would not be a source of personal disparagement. Given all the contact I have had over the years with participants in our hands-on courses I know we are on the right track and helping dentists be more aware of the options that are available.

Regards, Barry