A Lack of Critical Thinking: The Factors That Determine The Quality Of Our Endodontic Education

Given the market mentality that has taken over a good portion of our endodontic education, one can discern a divide between those aspects of learning that are not related to the eventual purchase of a product or service by the student body and those that are. Differential diagnosis, being educated to differentiate the various stages of pulpal disease is pretty much devoid of commercial endeavors. That is also the case in learning the various stages of tooth development and what those tissues look like at the histologic level. With nothing to be sold in these areas of education, the pursuit of knowledge is not subject to any influences that might distort its unbiased dispersal to the student body.

That is not the case where a product or service is involved. And not coincidentally, it is in these areas that we find corporate involvement in the educational process most apparent. Corporate influence in cooperation with school administrations determine what instrumentation systems will be employed by the students, which sealers will be used, whether or not a thermoplastic obturation system will be employed and then what brand will it specifically be. These choices are based on the corporations that are most generous in the financial terms they offer the dental schools.

One might conclude that such an arrangement is beneficial for both the corporations and the dental schools. The corporations will eventually be rewarded for their generosity by the eventual purchases by a graduated student body, the schools have their overhead lowered and the students who would be using a system that is equivalent to the others are losing nothing in using the system that is most financially beneficial to both the corporations and the schools. So, what are the downsides of this approach?

If we are serious about education, to be consistent, that education at least on the academic level if not clinically should include how alternative systems are employed and what are the advantages and disadvantages of employing them in comparison to the systems that are assigned by the schools to be used by the student body. This approach takes on relevance for the simple fact that the imposed systems come with shortcomings. Every rotary system is vulnerable to instrument separation. Every rotary system has been shown to inadequately cleanse oval canals. K-files used to create the glide path tend to impact debris apically resulting in loss of length. Those teaching these systems are well aware of these shortcomings and have devised modifications in the use of rotary NiTi to minimize instrument separations. Yet, as has been documented in multiple studies, the precaution of centered shaping that reduces the incidence of instrument separation tend to exacerbate inadequate debridement, a natural consequence of using the rotary instruments more conservatively.

So, yes, the shortcoming of instrument separation is recognized and addressed by employing them in the centered position that further undermines debridement and that is accepted as the solution to instrument breakage. Inadequate debridement is the price that must be paid to keep the instruments more predictably intact. What is missing in this response?

For one, a solution that solves one problem at the exacerbation of another is not a solution. Of more importance is the complete absence of asking why these shortcomings exist. The importance of asking why is crucial to devising solutions that overcome all the shortcomings including breakage, inadequate debridement and the apical impaction of debris. So why do the instruments break? Rotation, particularly as canal curvature increases, produce torsional stresses and cyclic fatigue the two factors that are associated with instrument separation. If either torsional stresses or cyclic fatigue independently or in combination exceed the elastic limit of the NiTi instruments separation results. Knowing this, one possible solution is to significantly reduce the arc of motion to a fraction of a full arc thereby reducing the torsional stresses and cyclic fatigue that the instruments are exposed to.

This particular solution has been has been tried and validated in studies comparing various rotary NiTi systems with 30o oscillating stainless steel relieved reamers where all rotary systems separated within two to three minutes and the 30o oscillating reamers remained intact through repeated 5 minute cycles. The conclusion is obvious. Confined to short arcs of motion the instruments remain intact. Clinically, this approach has led to the complete elimination of separations. Such invulnerability also eliminates the need for the instruments to stay centered giving the dentist the freedom to apply them vigorously against all the canal walls providing superior debridement as confirmed in the French study that I have posted in the past.

If the schools were truly educating the students, they would cite the evidence that a system designed to eliminate instrument separation now gives the dentist the increased ability to more thoroughly cleanse the canals. Unlike rotary NiTi where the steps needed to reduce instrument separation results in poorer debridement, the 30o oscillating reamers positively address the problems of instrument separation and thorough debridement at the same time. The educational programs at the schools funded by the chosen corporation based on its financial generosity are obligated to avoid any discussion that involves alternatives to the shortcomings of rotary NiTi. The unstated but blatant fact is that the corporations have made an investment in the schools' education programs that must be rewarded to continue in future years. The schools are counting on this continued investment and know if open access to a broader education regarding endodontic mechanics were taught they would lose corporate support and at this stage of the game, that is not an option.

What about K-files being associated with the apical impaction of debris? That is a problem and is there anything to be gained by an analysis of why this occurs? Indeed there is. A basic mechanical principle is that form either follows function or the two are immediately tied together. Either way, the form (design) of the instrument will determine how it functions. Dentin is shaved away from the canal walls when the flutes are more or less at right angles to the plane of motion. In the case of K-files with their predominantly horizontal flute orientation, the dentin will be shaved away most effectively with the pull (vertical) stroke. When inserted into the canals those same predominately horizontal flutes acting now as plungers will tend to impact debris apically resulting in the loss of length noted by those using them.

If one understands the correlation between apically impacted debris and the horizontal orientation of the flutes, it becomes much easier to ask what will happen if instead of the horizontal flute orientation of a K-file we would employ an instrument with predominantly a vertical flute orientation, namely a K-reamer. Rather than shaving the dentin away on the pull stroke as is the case with a K-files, the K-reamer shaves dentin away with the instrument’s horizontal rotation. They have little ability to shave dentine away on the pull stroke. In the same way, when inserted into the canal, the K-reamers are inefficiently designed to impact debris apically and that is a good thing.

The schools take no effort in tying form to function even in the most basic instances when a K-file is first used in the creation of the glide path. If they did, it would be understood that the K-reamers offer a superior design for the tasks they are asked to perform. The inadequacy of the schools’ performance in teaching basic mechanical principles is further demonstrated in describing rotary instruments as NiTi files. As noted earlier, files are designed to be used with the pull stroke, but rotary files are used in rotation. Now look at the flutes on any rotary instrument being manufactured today and you note they have a reamer orientation, not that of a file. And it makes sense given their use in rotation.

So what is the big deal? The improper designation reflects a lack of education in basic endodontic mechanics. It is imperative that students in their endodontic education know the difference between a reamer and a file and the impact design has on function. By misnaming a rotary reamer as a file, the teachings the students receive is compromised, perhaps because the teachers themselves are unaware of the differences and the implications that follow. Without knowing the difference between a reamer and a file and the way they function, the K-file is still employed in the creation of the glide path and blockages will still occur. From a commercial point of view, this is not displeasing to the corporations supporting these courses. The more difficult it takes to create a glide path with K-files, the more attractive it is to start employing rotary NiTi earlier. If one uses K-reamers rather than K-files the creation of the glide path is that much easier with a reduced possibility of impacting debris apically and the possibility of using these instruments generally invulnerable to breakage, due to the short arcs of motion with which they are used, to create wider preparations.

As it turns out, the K-reamers used in the oscillating handpiece offers an almost complete alternative to the use of the vulnerable rotary instruments. Confined to 30o arcs of motion at a frequency of 3000-4000 cycles per minute, this method of instrumentation completely eliminated instrument separation, provides for three-dimensional debridement, eliminates practically all hand fatigue and dramatically speeds up the instrumentation process. There is no way that the corporate sponsored endodontic programs in the schools are going to teach this alternative system even though it offers a unique solution to the problems that are all to familiar with those employing any one of the rotary systems available.

By understanding the mechanics of the instruments, it became apparent that minor modifications of the K-reamer were all that was necessary to further improve their performance. By placing a flat along their working length, they became that much more flexible without increasing their vulnerability to separation. By limiting their arc of motion to 30o they proved to be even more efficient at negotiating curved canals without inducing distortions than the manual balanced force technique that was limited in its use in bucco-lingual lateral movement and rapidly induced manual fatigue. These are not facts that a corporate sponsored endodontic education program will discuss. Indeed, the policy of the schools I am acquainted with prohibit the discussion of any alternative means of instrumentation on school grounds. So much for the schools’ contention that the attainment of critical skills is the most important goal of the education process.

We are creatures of the educational process we have been subjected to. That does not mean we are forever hamstrung in our thinking. It just makes for a greater challenge. My goal is for the reader of these posts as well as myself to expand my mind and not be limited by a corporate environment that wishes to dictate what we should think and most important to them purchase.

Regards, Barry