Rationale versus rationalizations

I’m presently reading a book on Lincoln that extols his search for truth regarding slavery in the United States. Just prior to the Civil War, Steven Douglas was the main proponent of a concept called “popular sovereignty,” a plan that would decide if the new states being opened in the west would be free or slave. It was Douglas’s contention that nothing is more democratic than the people deciding what type of social network they could set up. The states would retain their freedom of action over that of federal authority and the South would not feel that their society and economic backbone were being threatened by slavery’s eventual elimination. What I get from this argument is that Douglas was using “popular sovereignty” as a rationalization for the continuation and expansion of slavery declaring nothing could be more democratic than a free people having the right to expand slavery’s hold on the nation.

Lincoln understood early on that the use of the so-called democratic practice of “popular sovereignty” manifested a far greater evil, that it went against our basic concepts stated by the Founding Fathers that “all men are created equal”. To use “popular sovereignty” as a vehicle to further slavery is in my mind an excellent example of rationalization for extending evil. Despite the fact that some of the Founding Fathers had themselves slaves, there is no historical record that the concept of “all men being created equal” did not include those from African descent. There is no historical record that the Founding Fathers were going to extend slavery beyond where it was when the nation was first established. Lincoln’s rationale rather than rationalization was based on a concept of universal truth, at least for our country, that all men are created equal and that any statutes that might be legislated to give some men the right to own others was ultimately self-destructive. For us not to believe in this most basic of principles undermines our very existence that for many generations is at the heart or should be at the heart of the type of society we wish to be. If we understand our roots, we can more easily distinguish between a solid rationale and a rationalization that goes against our long term best interests. It took the genius of Lincoln to see what was most basic for the good of our society.

Well, certainly that particular example of the differences between a rationale and a rationalization dwarfs just about any other example. I was just so moved by the rational arguments put forth by Lincoln in exposing Douglas’s rationalizations, rationalizations that at first blush appear to be consistent with the principles of a free society, that I had to include it in this article.

I believe that much of the support for rotary NiTi is based on rationalization rather than a solid rationale. Here’s my point of view.

Rotary NiTi has replaced some of what K-files did in the past because it does it better. By better, we mean that these instruments in one way or another negotiate to the apex more quickly and without as much distortion as the previous system based on K-files alone (fig 1). They are certainly not better in tracking the initial glide path because K-files are still required for this initial part of canal shaping. So rotary NiTi is really more an adjunct to the use of K-files rather than a substitute for them. Those rationalizing the use of rotary NiTi are saying that they represent a new technology that shapes canals more effectively and they present these systems as self contained entities when in reality they require the support of the very systems they are proclaiming to replace. Furthermore, a little common sense would make it very clear that K-files are the wrong instrument to use for initial glide path creation. We can say this with assuredness because as soon as the glide path is created, we use rotary files that are really not files at all. They are reamers. They are used in rotation and have flutes that are far more vertically oriented than those on a K-file. It is a reasonable question to ask why K-files would be the initial instrument used for glide path creation when as soon as that path has been established the instruments replacing the K-files are those designed and used as reamers. In fact, the use of K-files is a poor choice as evidenced by the use of instruments that are designed as reamers even though they are still designated as files, something that helps no one in understanding the mechanics of canal shaping.

To continue to advocate the use of K-files when K-reamers and relieved K-reamers (SafeSiders) (fig 2) work so much more efficiently furthers the rationalization for the use of rotary NiTi without strengthening its rationale argument for their use. One must ignore the great improvements in initial canal shaping that relieved reamers bring to the table to justify the use of rotary NiTi. If one employs the benefits derived from relieved reamers used either manually with a tight watch winding stroke or in the 30º reciprocating handpiece (fig 3), one quickly realizes that the glide path created with these instruments amounts to no more than the start of their effective usage. They may be used with great efficiency and safety thru the entire shaping procedure opening even highly curved canals to a minimum of 35 with a 25/06 overlayed taper. It is this reality that represents the rationale argument for their use. It takes the denial of the effectiveness of these instruments or simply ignoring them to justify the use of far more expensive and vulnerable rotary NiTi systems. Because simpler, safer and less expensive means exist to shape canals, the advocacy of rotary NiTi must by default be based on arguments that represent rationalizations for their use. Once the most obvious alternatives are eliminated from discussion, those advocating rotary NiTi must emphasize all the limitations that are imposed on rotary NiTi systems, namely the factors that aggravate the torsional stresses and cyclic fatigue that plaque all rotary NiTi systems. Over the years this list of limitations has grown more and more with greater and greater burdens placed on the operator using these systems. The ultimate rationalization is that the cause of failure is based on the incompetence of the practioner and not on the design and delivery of the rotary NiTi systems where at least some of the blame should be fairly placed.

The consequences of rationalization as applied to the support of rotary NiTi instrumentation places a number of burdens upon the practioner including:

1. instruments that are prone to fracture if they encounter excessive torsional stress and cyclic fatigue. (Fig. 4);

2. to minimize the breakage that occurs because of excessive torsional stress and cyclic fatigue the dentist must avoid the following situations:

   a. canals that dilacerate, merge, bifurcate and recurve
   b. a crown down technique must be employed that often requires a good deal of recapitulation
   c. the application of minimal apical pressure
   d. their frequent replacement
   e. minimal apical preparation, often less than required for effective cleansing and shaping to afford adequate irritation;

and

3. a long learning curve.

Every limitation for rotary NiTi means that an alternative system must be used in its place. The necessity for this substitution undermines the rationalizations that the advocates of rotary NiTi espouse. What is the advantage of a new technology that has a myriad of limitations especially when safer and more predictable alternative methods will do a better job than the so-called superior rotary NiTi technology? The rationalizations for rotary NiTi by clever marketers has not removed its vulnerabilities, has increased the number of instrument breakages, has reduced the endodontic challenges that some dentists are willing to take and has increased the cost by a factor as high as 30 times over that of reciprocating relieved reamers on a per use basis. These weaknesses would not be papered over except for the creation and exhortations of misapplied principles for the express purpose of redirecting those weaknesses to the responsibility of the dentist as opposed to the manufacturer that in my mind is where they truly belong.

On the contrary, arguments for the use of relieved reamers must be rational because they consistently deliver on what is logically concluded from their design and method of delivery.

1. They are virtually invulnerable to breakage because the two factors that cause separation, torsional stress and cyclic fatigue are for the most part entirely eliminated.

2. They are used safely at oscillating speeds of 3000-4000 cpm.

3. They have more vertically oriented flutes that cut efficiently when the horizontal motion of the reciprocating handpiece is incorporated

4. They are more flexible, less engaging and produce a superior tactile perception for the dentist compared to k-files

5. Unlike either K-files or rotary NiTi the relieved reamers can easily distinguish between hitting a solid wall and engaging a tight canal as well as differentiating between a round and oval canal. Recognizing both these conditions tells a dentist when to prebend an instrument, how to negotiate around a blockage and when to reattach the instrument to the reciprocating handpiece. As one might expect, oval canals require greater instrumentation to remove tissue that might be lurking in their wider extensions and at a minimum create a larger space for more effective irrigation to dissolve tissue that was not removed mechanically.

The above points represent rational arguments for their use and most importantly do not misdirect the dentist away from any hidden weaknesses that can come back to haunt him at a later date or a more challenging endodontic situation that with other systems he would be reticent to tackle.

Another example of rationalization versus a solid rationale includes thermoplastic obturation. Supporters of thermoplastic systems emphasize their advocacy based on the adaptation of flowable gutta percha to the canal walls which in turn drive the cement into all the nooks and crannies of the canal. To justify their advocacy they must deemphasize the fact that thermoplasticized gutta percha shrinks about 4 to 5% as it cools to body temperature and this contraction occurs only after the cement has been displaced. To admit the latter is to weaken their argument. Rationalization is not a search for the truth. It is a guide for supporting a system with weaknesses and either covering up or attempting to ignore those weaknesses. The last thing a rationalization is, is an honest attempt at coming to terms with those weakenesses.

The rationale for a system based on a room temperature cement system starts with the premise that a canal can be flooded with a cement that does not shrink upon polymerization, and binds chemically and physically to both the gutta percha and the canal walls. Given the attributes of this cement, it can be coupled to a master gutta percha point that fits any given canal with at least 85% accuracy throughout its length and probably close to 95% accuracy in the apical third. This gutta percha point in turn can be well coated with this same cement and placed into the canal. Between the well-fitted and well coated gutta percha point and the flooded canal we have an excess of obturating material. The cement more flowable at room temperature than thermoplastic gutta percha will be driven laterally and then escape coronally obturating any auxiliary canals along the way. In addition, both the gutta percha and the cement were placed at room temperature and warm to body temperature expanding about 1.75% in the process creating an even better seal. It is the above description that is the rationale for their use. There is no apparent rationalization that I can see. Techniques based on their rational use rather than a rationalization of their use stand a far better chance of being successful clinically. (Figs 5-7)

I’d be curious if any one else out there can think of examples of rationalization versus rationale argument. It’s a good exercise in attempting insightful analysis, something that Lincoln did so well and tells us such a great story close to 150 years later.

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