Separating What’s Real From What Is Claimed To Be Real In Endodontic Instrumentation

What’s claimed: Using rotary NiTi with the series of well-known precautions virtually eliminates instrument separations and does not compromise debridement. That is false.

A perusal of the endodontic literature still documents rates of instrumentation using rotary systems that vary between 2% and 6%. Indeed, there is routine continuous documentation of such iatrogenic events right here on linkedin. So, one may conclude that these separations result from the inadequate application of the recommended precautions. One may also conclude that it is the application of these precautions that keep the breakage rate to between 2% and 6% where it would be much higher if they were not implemented. If this is the case, then we must accept the fact that some degree of separation is unavoidable using a rotary NiTi instrumentation system be it continuous or interrupted, that given the present state of technology it is inherent to systems that produce torsional stresses and cyclic fatigue that at times exceed the elastic limit of the NiTi resulting in the separations we so much want to avoid.

. What’s claimed: Rotary NiTi does not induce dentinal-micro-cracks. That is false.

Hundreds of papers have documented the relationship between the use of rotary NiTi and the production of dentinal micro-cracks. Many studies include sectional observation of extracted teeth at 3mm, 6mm and 9 mm from the apex of teeth that were subject to rotary NiTi instrumentation as well as controls that were not. Those subject to rotary instrumentation consistently produce far more dentinal micro-cracks than the controls that were not subject to rotary instrumentation. Advocates of rotary NiTi claim these results are artifacts of the research protocols, that they would not exist in a real clinical situation. They claim that the sectioning of the teeth produces the dentinal micro-cracks and not the process of rotary instrumentation. If that were the case, it still does not explain the higher incidence of micro-cracks observed in those teeth that underwent rotary instrumentation compared to the controls. Furthermore, a number of non-destructive studies have been done using micro-ct scans that show a significantly higher number of dentinal micro-cracks in teeth after rotary instrumentation than were present in the controls. To this, rotary advocates state that using extracted teeth even though they are kept hydrated results in artifacts that would not occur in teeth that are in the mouth. To support this contention, a cadaver study of teeth retained in the mouth and subject to rotary instrumentation produced results that showed no increase in dentinal micro-cracks after instrumentation concluding that whatever micro-cracks exists after instrumentation were present before instrumentation. Interestingly, this study used a voxel size of 14.5 when scanning the teeth compared to the use of a voxel size of 5 employed in the previous micro-ct scans. The smaller the voxel size the greater the detail generated in the images. A voxel size of 14.5, almost three times larger than the voxel size used in the other studies results in far less detail.

From the perspective of common sense, the overriding reality is clarified by referring to Newton’s Third Law of Motion that states that two interactive bodies in this case the canal walls and the rotating NiTi instruments have an equal and opposite effect on each other. It is documented beyond doubt that the canal walls can cause the rotating instruments to separate, something that is all too obvious. Rotary advocates who deny the production of dentinal micro-cracks resulting from rotary NiTi instrumentation are stating that Newton’s Third Law is not operative, that yes, the canal walls can induce instrument separation, but the instruments have no potential to impact the canal walls. In short, Newton’s Third Law of Motion is a one way street. Their conclusions defy critical thinking and defy logical thinking.

On the contrary, there is a direct relationship between rotary NiTi and the production of dentinal micro-cracks. That is true.

. What is claimed: The only alternative to rotary NiTi is the manual hand fatiguing and time consuming use of K-files. That is false.

As I have discussed in many posts over the years, we substitute relieved stainless steel reamers for K-files that are engine-driven in 30o arcs of motion at a frequency of 3000-4000 cycles per minute. This engine-driven system minimizes hand fatigue and dramatically shortens the procedural time requirements. Its most obvious advantage over rotary NiTi is that confined to such short arcs of motion, instrument separation is completely eliminated. Because of its inherent safety, it makes sense to prepare as much of the canal as possible. Seen in this light, we prepare 98% of the canal shaping and cleansing employing these high frequency stainless steel relieved reamers through a size 35/04 or 30/04 in the majority of cases before using a single 30/04 helically relieved rotary NiTi instrument to smooth the mesial and distal canal walls and size the prepared space for the appropriate gutta percha point. By this time the single rotary instrument we use encounters minimal resistance with only a few full rotations necessary to reach the apex, greatly reducing any chances of instrument separation.

. What is claimed: NiTi due to its greater flexibility will produce less distortions when instrumenting curved canals than any stainless steel instrument. That is false.

Again, referring to the past endodontic literature, Dr. James Roane clearly documented the ability of stainless steel K-files confined to short arcs of motion to stay true to the original canal anatomy defining his procedure as the balanced force technique. The use of 30o oscillating reamers at a frequency of 3000-4000 cycles per minute has improved on his use of K-files. By using relieved reamers that are more flexible than K-files, have fewer and more vertical flutes than K-files that encounter less resistance on the way to the apex and employing shorter arcs of motion than he employed in the original balanced force technique, we improve the speed of the procedure, further reducing the potential for canal distortion while eliminating any chances of instrument separation. In short, rotary instrumentation required the development of NiTi that even in its latest iterations is still prone to separation and the production of dentinal micro-cracks. The use of stainless steel relieved reamers took a different and safer tract, limiting the arc of motion to the point that the elastic limit of the instruments are never exceeded eliminating separations and conforming to the principles of the balanced force technique in terms of canal preparation without distortion regardless of the degree of curvature present.

. What is claimed: Rotary advocates claim the superiority of the instrumentation system determines what is most successful in the market. That is false.

What determines success in the market is determined by those companies that have the most money to invest in marketing. In the case of rotary NiTi instrumentation systems that are produced by the wealthiest of manufacturing corporations, they dominate what is taught in the dental schools by offering major sponsorship of their products. This sponsorship saves the schools a lot of money and the exclusive access to the student bodies are based on the most generous sponsorships. Please note the term exclusive, meaning that any information detrimental to the marketing potential of these products is prohibited from being dispersed to the students. It is an agreement between the schools and the sponsoring corporations for their mutual economic benefit while the students are treated most notably as future consumers. Not exactly an environment that encourages the development of critical thinking skills what used to be considered the most important part of education.

The dichotomy in endodontic education that results from commercial goals:

. Rotary NiTi manufacturers and their advocates have made major efforts to diminish the importance of the fact that rotary NiTi instrumentation is prone to instrument separation.

That is true.

They employ the following arguments:

. All instruments are prone to separation. False.

. If you follow the precautions for rotary NiTi, the instruments will not break. False.

. Following the precautions does not compromise the effectiveness of rotary NITi. False.

I am about halfway through this post separating the real from the hype and will write the rest of this discussion in the next post. It takes a bit of time to wrap one’s head around the interplay of education and marketing and how each effects the other. I think, however, it is a good exercise in developing our own critical thinking skills, the ultimate protections we have in determining what is valid and what is not.

Regards, Barry