Why Critical Thinking Determines 30o Oscillating Reamers As A Most Effective Means of Instrumentation

I asked myself if there is a way to shape all canal configurations from simple to complex without the concern for instrument separation. One usable answer is to limit the arc of motion to a degree that that any torsional stress or cyclic fatigue?generated would not exceed the elastic limit of the metal. That is accomplished by employing the instruments in a 30o oscillating handpiece.

Is there a way to assure greater three-dimensional debridement in all canal configurations?from simple to complex? The primary need to eliminate separation by employing the instruments in short 30o arcs of motion automatically accomplishes the goal of superior?debridement by the instruments now having the ability to be vigorously applied to all the canal?walls, something one can now do knowing that the instruments will remain intact.

Is there a way to apply such vigorous instrumentation in all canal configurations from simple?to complex without inducing distortions? It turns out that the 30o arcs of motion even at the high frequency of 3000-4000 cycles per minute stay true to the original canal anatomy.

Given the 30o oscillations generated by the handpiece, is there an optimal instrument design?that best accomplishes the above goals? Since the handpiece is generating short horizontal?arcs of motion at a frequency of 3000-4000 cycles per minute, the blades of the instruments?should be more or less at right angles to the plane of motion to most effectively shave dentin?from the canal walls. Stainless steel reamers rather than K-files are designed with a more vertical flute orientation that best shaves dentin away when the 30o arcs of motion are generated by the handpiece.

What else can be designed into these stainless steel reamers that give them greater ease at?negotiating through the lengths of the canals? By creating a flat along the working length of?canals more effectively. The flat along length creates two vertical blades in addition to the?vertically oriented flutes that shave dentin away in both the clockwise and counterclockwise motion of the instruments.

Given the problem of dentinal micro-cracks generated by rotary instruments, do the short arcs of motion generated by the 30o oscillating handpiece reduce the likelihood of inducing dentinal defects in the canal walls? In accordance with Newton’s Third Law of Motion, the same short arcs that keep the instrument intact have far less potential to induce the defects produced in full rotation whether or not those rotations are continuous or interrupted.

How effective is 30o oscillations at minimizing apically extruded debris and how does it?compare to other systems? The system that produces the greatest amount of apically?extruded debris is the manual use of K-files uses in the traditional twist and pull manner. The?push stroke applied with the in stroke causes the predominantly horizontal flutes to act as a?plunger on any debris present in the canal driving it apically potentially resulting in blockages?that lead to loss of length as well as extruded debris. If K-files are used with the balanced?force technique the plunger effect is removed and the amount of impacted or extruded debris?is dramatically lessened. From the perspective of extruded or impacted debris alone the balanced force technique is the best way to avoid it. However, the balanced force technique?is a slow manual hand fatiguing process that is not designed to cleanse oval canals and,?consequently, for most dentists it is not a widely adopted despite the relative advantage in?this one area of endodontic instrumentation.

While 30o oscillations of stainless steel relieved twisted reamers will produce some small amount of extruded debris, it is no more than that generated by the rotary instruments and a lot less than the K-files that are used to create the glide path prior to rotary’s use. And we should never lose sight of the fact that rotary has never eliminated the disadvantages of instrument separation, inadequate three-dimensional debridement of oval canals and thin isthmuses and the increased potential to induce dentinal defects.

On balance, again from my perspective, the advantages of 30o oscillating relieved reamers clearly outweigh those of any other approaches when all the factors are taken into consideration. One might add to the list of advantages the fact that they can be used several times times replaced only when they become dull rather than any concerns regarding instrument separation. And simply knowing the instruments will remain intact regardless of the canals they are negotiating through reduces procedural stress significantly. So, we came to developing, adopting and advocating for this form of instrumentation. It was and is a product of critical thinking, understanding the mechanisms of action of the systems available, the limits of each and then devising designs and methods of implementation that accentuated the positives while reducing or eliminating the negatives.

Interestingly, even in the one area, extruded apical debris, where it has not been completely eliminated, the impact of apically extruded debris according to recent research does not affect clinical success rates. While rotary advocates point to selective studies stating rotary may result in reduced amounts of apically extruded debris, it should be noted that prior to their use the glide path is created using K-files using the traditional twist and pull motion, a technique that as mentioned earlier has clearly been shown to produce the greatest amount of apically extruded debris.

These same questions that we posed to ourselves can now be directed at ChatGPT using the same research and clinical experience for further insights. In future posts, I will be displaying the interactions we have with ChatGPT in the ongoing quest to better understand what works best in endodontic instrumentation.

Regards, Barry