The Need For Applying Common Sense To Endodontic Procedures

What does it mean to apply common sense and are there steps we can take to make our common sense more informed? We have been indoctrinated to believe that we must cleanse the canal systems as much as possible, yet in multiple research studies comparing the debridement of different systems do we find a correlation between improved outcomes as a consequence of marginal differences of the tested systems. The same outcomes are noted for comparative studies on canal distortions, debris extruded, degrees of access. The various studies delineate superiority of the mechanics of one system over another, but again they do not connect these results to superior outcomes.

Given the neutral impact of the various aspects of canal instrumentation on outcomes, despite enhanced mechanical results do we have any more valid way to make decisions on what to use? It is here where we want to employ common sense to see if we can construct a protocol that that can correlate to more successful outcomes. To see if this is possible, let’s get to a point in canal instrumentation where it becomes completely obvious that the employment of a particular step or its absence will impact the success of treatment.

For me the first thing that comes to mind are the many cases that I have treated over the years involving the mb2, the additional canal that is typically present in the mb root of maxillary first molars. I have had to retreat many of these roots because of the presence of periapical infection, a result of a previous treatment that missed mb2. Upon retreatment, the infection present on the mb root resolved. What this sequence of events tells us is that missed canals are a cause of infection and that finding and removing the tissue and bacteria that resided there leads to a positive outcome. Now this is pretty basic, but we don’t want to extend our assumptions for success beyond what is most obvious.?

How far is it reasonable to extend the concept of uncleansed canals as a source of infection while implying that cleansing them will result in superior outcomes? How about a canal that is blocked due to a separated instrument? The blocked canal prevents it from being debrided as well as one not blocked. Depending upon the state of the canal prior to instrument separation, the periapical tissue may or may not become infected or if already infected have a varied chance of resolution depending upon how debrided the canal was prior to the separation. Our common sense can appreciate the fact that success or failure of a canal with a separated instrument can vary, but it also tells us that overall we are better off if the separated instrument were not present in the first place.

That insight in turn motivates us to prevent instrument separation. We know that rotary instruments are more prone to separation as the canal anatomy they are negotiating through becomes more complex. This particular observation has been amply demonstrated in mechanical stress studies that are completely detached from treatment outcomes. One of the key precautions in keeping rotary instruments intact, is to use them in a centered fashion that discourages vigorous lateral movement, reducing the flexural stresses they are exposed to. In canals round in cross-section this limitation does not result in compromising debridement. However, in oval canals or pulpal configurations that include isthmuses and elongated flat anatomy, centered shaping confined to the least resistant portion of the canal results in a good portion of the canal walls not being touched leaving the tissue residing there in place.?

While the research clearly and unequivocally demonstrates the remaining tissue, again there is no study that correlates such results as impacting the outcomes of treatment. It is issues like this, that common sense comes to bridge the gap between the absence of confirmatory data and what is most likely reality. We know missed canals can lead to periapical infection. We make the reasonable assumption that canals that are only partially debrided have a greater chance of producing periapical infection. We know that rotary leaves tissue in oval canals, isthmuses and flat pulpal configurations. It is reasonable to assume that outcomes will be negatively impacted the greater the amount of tissue and bacteria left in the confines of the canal. No study confirms this likelihood, but it defies common sense to assume that leaving tissue and bacteria in the canals has no consequences.

Guided by these reasonable assumptions, do we have the means to overcome the inadequate debridement of oval canals, isthmuses and flat pulpal configurations? We know that rotary NiTi is associated with instrument breakage and the precautionary steps devised to prevent it that compromise the cleansing of complex pulpal anatomy. Again, without any correlation to outcomes, high frequency 30o oscillations of stainless steel relieved twisted reamers have been shown to be virtually immune to separation even in the most highly curved canals, that short arcs of motion unlike rotary NiTi gives the dentist the ability to apply these relieved reamers aggressively against all the canal walls. I know from the cross-sectional studies we did on extracted teeth that the canals were well-debrided along their entire lengths and consequently, again make the reasonable assumption that employing these instruments result in cleaner canals regardless of the amount of canal curvature that is present. The research does not correlate improved debridement with superior outcomes, but common sense tells us that improved debridement can only increase success. To think otherwise, that improved debridement has no positive impact goes against our most basic observation that missed canals are responsible for periapical infections.

As for other aspects of canal preparation, confined to short arcs of motion the stainless steel relieved twisted reamers have been shown to negotiate curved canal anatomy without any obvious distortions, that they are far less prone to produce dentinal micro-cracks than rotary NiTi, that their high frequency coupled to direct contact of the canal walls along length are all aspects that at the common sense level are positives regarding canal preparation even though once again no correlation has been found between studies of canal distortions, dentinal micro-cracks and levels of debridement. To negate our common sense would leave us in a void that to date has not been filled with definitive data supporting one approach over another. Under present circumstances, not to nourish common sense starves us of our most precious gift, a creative and insightful mind.

Regards, Barry