Taking the Measure of Various Endodontic Instrumentation Techniques
Too often in comparing various endodontic instrumentation techniques the process is thought of as a zero sum game. One’s gains are another’s losses and from a monetary point of view there is a good deal of truth in that observation. Yet, in comparing different systems, the monetary impact on sales really should not be a consideration. If we can divorce these considerations the evaluation process can be strictly limited to their clinical capabilities that obviously will have an impact on sales, but should not be part of the evaluating process. Achieving this state of comparison is difficult because negative responses are likely to be quite rigorously rebuffed when they are directed at products produced by major manufacturers who as part of their marketing effort have mutually beneficial relationships with many academic endodontists.
Examples of rigorous responses include a number of articles that expressly state that rotary instruments do not produce dentinal micro-cracks. These articles contradicted a vastly larger body of research covering a broad range of experimental protocols that determined that rotary instrumentation does produce dentinal defects. These negative observations would likely not have been published if rotary were a minor product . In fact, if rotary were a minor product the research testing its impact on the integrity of canal walls would probably never have been published in the first place. That, however, is not the situation. Rotary dominates the market. Its sales are huge and constitute a major percentage of the profits the manufacturers receive. It is because of their large sales that a response to negative information is so vigorously attended to. The first order of business is to protect their market.
Other examples of mollifying negative outcomes include the downplaying of rotary instrument separation. Mollification here includes different approaches including:
A poll of Saudi dentists cast doubt on the above conclusions. Their poll included Saudi general dentists and specialists with the clear finding that separation was directly tied to the number of procedures performed regardless of experience, that endodontists experienced more separations simply because they performed more procedures. 83.1% of the respondents experienced complications while using rotary NiTi with the instruments’ fracture significantly the most common complication. The greater the number of weekly performed RCTs and participants experiences, the more rotary NiTi fractures and the greater the number of fracture incidences. The data from the poll concluded that fracture incidence was the most common complication while using rotary NiTi regardless of the clinicians’ skills. While the single use may reduce rotary NiTi fractures, the greater number of RCTs performed per week was the most influential factor.
This poll was published in a Saudi journal online in 2019 and would likely have had a greater impact on appreciating the risks involved in rotary instrumentation if this information had made its way into a major American or European endodontic journal. It is not surprising that it did not.
Other rotary studies have documented the poor cleansing and shaping when preparing oval canals as well as long narrow pulpal configurations that prevent the penetration of rotary instruments. The documented poor cleansing of rotary is mollified and justified by stating incorrectly that the first priority is to keep the instruments intact. That is not the first priority. The first priority is adequate cleansing of the canal and if rotary is not up to the task, other means must be used to compensate for its inadequacies.
The supporters of rotary NiTi don’t argue that point. They simply state that the function of the irrigants is to remove pulp tissue and bacterial biofilms via agitated and activated irigants. That is not what the studies show. The canals are well cleansed via a combination of instruments vigorously shaving dentin away from the canal walls and activated irrigants. Cleansing is dependent upon both. Oval canals and tight flat pulpal anatomy does not provide a space for the physical contact needed to adequately cleanse the canals as these research papers clearly document.
While rotary advocates deny that activated irrigation still leaves debris and bacteria in the recesses of oval and flattened pulpal anatomy, laser companies recognize rotary NiTi’s inability to cleanse these areas and have brought to market expensive laser activated irrigation systems to compensate for rotary’s inadequacies in these situations. Their inability to adequately cleanse these areas is based on the fragility of the rotating systems when aggressively applied laterally particularly when canal curvatures are already present, a reticence directly related to the false first priority of keeping the instruments intact.
The successful marketing of rotary NiTi making it the dominating technique to shape and cleanse canals provides them with a shield against negative research results. Having made a substantial monetary investment in their rotary purchases and possible educational courses, dentists are biased toward their successful utilization and often more than open to any rebuff regarding data that discusses their inadequacies. These dentists have a huge support system including their initial exposure to rotary systems as students, with follow-up support via numerous product reps well versed in giving advice on the safest means to use these instruments if and when problems arise. Numerous dental publications include articles displaying the impressive cases treated with rotary and the sequence of instruments that allowed them to gain those results. Any dental meeting is likely to include a number of courses sponsored by the major manufacturers and delivered by well-known endodontic academics.
These corporate support systems tend to retain the dentists as active consumers of the products they produce, a family so to speak that says we are with you through thick and thin. It is effective marketing blunting competition that may be addressing rotary NiTi’s limitations more effectively. I started this post by stating what would be ideal, a non-biased analysis of what works most effectively for the teeth being treated. With an attempt to apply the basics of logic, we want the instruments to remain intact under the most adverse of canal conditions. While remaining intact is not the first priority, it is an absolute necessity to achieve the first priority, namely adequate cleansing of the canal system.
A 30º oscillating handpiece generating motion at a frequency of 3000-4000 cycles per minute utilizing a combination of stainless steel twisted unrelieved and relieved reamers assures the dentist that the instruments will remain intact. Once this goal is achieved applying them vigorously against all canal configurations is now not only possible, but routinely doable.
From a common sense point of view, we are most likely to achieve maximum penetration into narrow canal configurations with our thinnest instrument, the 06/02 reamer, a tool when used in the oscillating handiece is virtually assured to remain intact regardless of how aggressively it is applied laterally or how tortuous the curve it negotiates on the way to the apex. The vertical blades shaving dentin away in small increments per cycle tends to rapidly reach the apex because of the high frequency of oscillations. We know the shaving process is effective because a canal offering major resistance to the 06/02 reamer is much looser when we skip to the 10/02, something that could only happen if the 06/02 effectively shaved significant amounts of dentin from the canal walls.
We accomplish our primary goal because we use instrumentation means that keep the instrument intact no matter the anatomical obstacles the instruments encounter giving us the freedom to apply these same instruments with vigor against all the canal walls and sonically activating the irrigants that enhance the physical removal of pulp tissue and bacteria that may be present. The fact that these oscillating instruments can tread where rotary fears to go may be construed by some rotary advocates as an attack on rotary. I prefer to think of 30º oscillating stainless steel reamers as an ever-present tool that can be employed if and whenever rotary negotiation of a canal system imposes risks of separation.
Oscillation is the answer to the safer usage of rotary. Just as rotary first replaced a protracted use of K-files minimizing time requirements and hand fatigue oscillating stainless steel reamers can create a space that limits the function of rotary to smoothing the canal walls and creating a space at least in the mesio-distal plane that matches the appropriate gutta percha point, a space that has been effectively widened to at least 90% of the dimensions of the final and only rotary instrument needed thereby subjecting this rotary instrument to minimal torsional stress and cyclic fatigue.
Regards, Barry
Chair & Program Director, Endodontics
2yAs opposed to CONSCIOUSLY, REPETITIVELY and UNASHAMEDLY BIASED.