by Dr. Scott T. Weed
Second opinions are common in health care, whether a doctor is sorting out a difficult case or a patient is not sure what
to do next. In the context of our magazine, the first opinion will always belong to the reader. This feature will allow fellow
dental professionals to share their opinions on various topics, providing you with a “second opinion.” Perhaps some of these
observations will change your mind, while others will solidify your position. In the end, our goal is to create discussion and
debate to enrich our profession. – Thomas Giacobbi, DDS, FAGD, Editorial Director, Dentaltown Magazine
A key review paper was published in 2007 by a team at the Eastman Dental Institute in
London, UK.1 Their work was of tremendous magnitude and attempted to pool the vast array of
outcomes studied in primary endodontic therapy from the previous 40 years. Part of their conclusion
states: “The reported success rates have failed to improve over the last four or five decades.”
How could anyone say our success rates haven’t improved?
Because they probably haven’t. The reason we’re not improving in our overall success rates
is because we focus too much on the things that matter the least. This is going to require a little
explaining on my part, so bear with me as I take a slightly circuitous course to a place I call
The Foundation: Science
The reality is we don’t completely understand endodontic disease, nor do we fully understand
how our endodontic treatments affect teeth long term (for good and for bad). Is it possible
that some of the things we do clinically to “fix” teeth might harm them over time? Don’t
we have literature to guide us—clinical science?
The purpose of science is to explain and predict. It’s like drawing a map. Listening to the
messages in endodontics today, it’s clear that many of our teachers have mistaken the “map” for
the “terrain.” That is, they think the way they understand things is the way things actually are.
The 20th century physicist E.T. Jaynes describes this as the Mind Projection Fallacy. The map
will never be the terrain and any inconsistencies between the two are always the map’s fault!
At a recent endodontic meeting here in the U.S., a well-known educator was asked, “What
is the explanation for [the high success rates of ] the millions of maxillary first molars that have
never had an MB2 canal uncovered or instrumented?”2 The answer: “I don’t know and I don’t
care.” Apparently explanation and prediction take a back seat when you think you’ve got
things figured out!
Specifically, you and I are interested in clinical research/science. We were all
taught certain principles of endodontics in dental school and these were presented
as doctrine. Straight-line access. X number of file sizes beyond the first file to bind.
Minimum apical file size. All canals visible at the same time with one eye closed.
(This could be a long list if we all got together and reminisced.)
You would think we had rock solid literature to back up all these recommendations. I’ve
come to the conclusion that where it counts, we are severely lacking in our science. The purpose
of clinical research is to inform the decision-making process. Each of us is confronted with
challenging clinical situations every day and we need to know what to do.
In briefly discussing science in this section, my purpose was to highlight some of the
uncertainty in what we do. Understanding uncertainty helps us better define and understand
Modern Endodontics: What It’s Not
Taking the exclusionary approach, let’s talk about what modern endodontics is not. Here
are a few questions:
Is modern endodontics about the latest and greatest secret sauce for irrigation? How about
sealers? New rotary files? What about lasers? Ultrasonics? Reciprocation? Cone-beam CT?
I want the silver bullet just as much as the next clinician, but if the research from the
Eastman Institute is to be believed, it doesn’t seem to work like that. My argument is that we’re
too focused on the small issues that can’t possibly have large effects on outcomes. Why do we
focus on these kinds of issues? Because they are “study-able.” It’s easier to compare leakage of
sealers in vitro than to conduct long-term randomized clinical trials.
So in a word, “no.” Modern endodontics is not found in the things mentioned above.
There isn’t some special sealer that will eliminate root canal failures. There isn’t an irrigation
device, sonic/ultrasonic/laser/etc., that will “clean away” failure. That’s because there’s a bigger
gorilla in the room.
The same authors at the Eastman Institute released several studies after the one I mentioned
before, all on outcomes of endodontic therapy. In their 2010 paper,3 the authors identified
four factors affecting failure of endodontically treated teeth: how the tooth is restored,
presence of adjacent teeth, involvement in a prosthesis and tooth type (molar versus non
molar). Which of these has anything to do with the actual endodontics?
First Things First
Renowned author and motivational speaker Dr. Stephen R. Covey talked about “First Things
First,” habit number three, in his popular self-help book, The Seven Habits of Highly Effective
People.4 An example of this principle in regard to population health is instructive. What would be
a more worthwhile endeavor: finding a cure for ebola virus or implementing the basic hygienic
practices of hand washing and quarantining of sick individuals? (There have only been 1,630
known cases of Zaire Ebola Virus Disease in the past 38 years since the disease was described.)5
Does it really matter which brand file you use if the case is going to sit for weeks in a stinky
cotton pellet and Cavit?
We need to start defining those strategies that make the biggest difference to the patient.
The old, outdated approach to endodontics is all about legacy systems and taking pride in
what we think we know (recall, “I don’t know and I don’t care”). Modern endodontics embraces
uncertainty and weighs risks and benefits accordingly. It is built on sophisticated decisionmaking,
excellence in execution and careful application of available tools.
When I graduated from dental school, I seriously embraced the idea that you find the
canal or perforate the root trying to find it. What a stupid philosophy. Sometimes our decision-
making skills only improve as we discard old ideas that impede progress.
One of these ideas is that we must do everything clinically based on some kind of scientific
study. There’s a problem with this. An exhaustive review of the literature on sodium
hypochlorite does nothing to inform our decisions in a clear way. Should we use full strength?
Half strength? Buffered? The literature offers us no such help in this simple matter. The same
could be said for most of the clinical decisions we make in endodontics.
This statement will draw criticism from many, and if you feel yourself wanting to argue
with this, consider that most measures of outcomes in our science aren’t actual outcomes that
affect patients. A bacterial count in a canal says nothing about how long the tooth lasts in the
In the absence of clear scientific guidance, I strongly feel our treatments should err on the
side of conservation of tooth. Teeth need to be drilled on as much as my chest bone needs to
be cracked open. Don’t do it. But if you must, be delicate and careful. Conservative treatment
is often more difficult to pull off than reckless treatment.
The concept of minimal invasion of
the tooth is taking hold, not because it’s
got rock solid scientific backing, but
because it just makes sense. I don’t need
a scientific study to tell me that drilling
on the tooth won’t make it stronger.
We need to put ourselves in the
shoes of our patients: What do they care
about? It’s pretty simple, really. They
want to keep their teeth and balance
that with the time, cost and aggravation
of making that happen. If it’s the tooth we’re trying to save with endodontics, why are we
drilling so much of it? Weak teeth don’t go the distance.
Excellence in Execution
How do I personally execute minimally invasive endodontics with excellence? The first
thing is magnification and illumination. I not only use a microscope, but I also have my chairside
assistant in the scope with me via a co-observation tube. She’s managing the field in an
aggressive way so I can see.
Second, I’ve abandoned the old tools and concepts that resulted in unnecessary dentin
removal. Straight-line access (SLA) has nothing to do with the long axis of the tooth and
everything to do with the location and angulation of canal orifices. I strongly question the old
dogma—“legacy concepts”—specific to canal preparation. Do I really need to open the canal
orifice larger than 1.0mm?
Third, excellence means knowing limits. I thoroughly discuss the limitations of my skills with
each patient. My practice is built on excellence and I can’t afford marginal results. It also means
that I aggressively follow up my cases. It’s easy to ignorantly think that everything we do “works”
and that we have little failure. If you aren’t seeing your own failing cases, someone else is.
Careful Application of Available Tools
If the essence of modern endodontics is preservation of tooth structure, we must discard
those tools that get in the way of this goal. If you saw my Townie Meeting presentation from
2013, you know how I feel about round burs for endodontic access. They are awkward,
destructive and prone to errors that needlessly sacrifice dentin. Long, slender diamonds are
much more appropriate.
We need the tools to be conservative—smaller tools. There are so many engine-driven
nickel-titanium files on the market yet they all do the same thing: they cut shapes in roots.
Whether they rotate or reciprocate or oscillate, it doesn’t matter. I’m looking for a file that cuts less. The feature of the file most directly governing how much a file cuts is the maximum flute diameter. If a manufacturer came to me and said, “What can I make for you?” I’d reply,
“Make me a file with less diameter at the shank.” The only reason to open the canal over
1.0mm at the orifice is convenience. Why weaken the tooth for convenience?
Smaller tools also include thin ultrasonic tips and tiny rotary burs with sufficient length
to do work in the pulp chamber. Obviously, this assumes you can see what you’re doing (back
to the magnification discussion).
3D imaging can be a tremendous benefit in elucidating tricky anatomy. It can be helpful
with diagnoses as well. I feel very strongly about the competency one must possess to own and
operate this technology. Unfortunately, there are few resources in dentistry to help us gain the
expertise necessary to maximize the benefits of this technology to our patients. Thankfully,
medicine has much deeper and broader experience in this realm.
Bringing it All Together
As a specialist, I often get questions from colleagues about specific materials and techniques.
I think it’s our formal schooling process that drives us toward laundry lists and cook
books and to make crib sheets.
I rarely have brand-specific recommendations unless it’s something I feel makes a big
difference in being conservative. For example, there are only so many files on the market
today with a maximum flute diameter equal to or less than 1mm. I can’t, in good conscience,
recommend files larger than that. It has nothing to do with their metallurgy, flute design, etc.
It’s simply a size issue.
As long as the clinician sticks to the tried-and-true material for endodontic treatments,
applies conservative access and shaping approaches along with careful technique, success rates
will be quite high. This means that all canals should be located and instrumented, irrigated,
obturated, and an immediate permanent core should be placed. Until I see other evidence,
these steps seem to predictably get cases to heal (although they are not always necessary given
the many “exceptions” to the rules we all see in our practices).
Modern endodontics isn’t about simply swapping out old for new product iterations while
keeping the outdated mentality of treatment. Modern endodontics is in the conservation of
dentin; it is in the skills required to practice minimally invasive dentistry; and it is in the careful
implementation in the proper tools.
The teeth harmed the least tend to last the longest. I encourage each one of us to examine
our work carefully and see if it might not be possible to drill a little less dentin next time we
perform endodontic therapy.
- “Outcome of primary root canal treatment: systematic review of the literature - part 1. Effects of study characteristics on probability of success.”
Ng YL, Mann V, Rahbaran S, Lewsey J, Gulabivala K. Int Endod J. 2007 Dec;40(12):921-39.
- Kulild and Peters showed 95% of these teeth to have 2 MB canals! “Incidence and configuration of canal systems in the mesiobuccal root of
maxillary first and second molars.” Kulild JC1, Peters DD. J Endod. 1990 Jul;16(7):311-7.
- Int Endod J. 2010 Mar;43(3):171-89. “Tooth survival following non-surgical root canal treatment: a systematic review of the literature.” Ng YL1, Mann V,
- Covey, S. R. (1989). The 7 Habits of Highly Effective People . 1989, NY: Free Press.
- J Gen Virol May 2014 vir.0.067199-0