Restraint: The Lost Art of Endodontics

Dr. John West


I have a confession. I am a dreamer! And, as such, I have always been obsessed by the power of ideas. It is that inward focus that has helped give me the confidence to share this overdue article about the forgotten endodontic word Restraint. Simply being aware of it can change how we see and perform in the world of endodontics. My idea is that you will be a measurably better endodontic clinician if you embrace the fundamental component of this article: Restraint as an essential ingredient for Mastering Endodontics.

For some, this article may be a hard read because it is not about a scientific endodontic technique, genius breakthrough, or products. For others, it has the capacity to change their experience of endodontics forever and transcend today’s newest technologies.

The key operating word is R-E-S-T-R-A-I-N-T.

The word “restraint” has not existed anywhere in the Journal of Endodontics (JOE) over the last 43 years (since the first JOE issue in 1975). A search on PubMed on April 12, 2018, returned zero results for the words “restraint” and “endodontics.” In addition, a similar lack of any “restraint” references exist for Dentistry Today (also searched on April 12, 2018), with only one relevant result for the words “restraint” and “root canal.”1

Two other clinical vocabulary words will facilitate readers’ lasting impact of this article: “Follow” and “Envelope.” First, “Follow” is the perfect word to describe manually following a curved file down an existing patent canal or patent part of a canal vs directing the file using manual motions, such as Watch Wind. In classic Watch Wind, the clinician attempts to direct the path of the file. “Following” instead allows the canal to direct the file, as if a child is sliding down a curved slide at the park. The slide’s walls direct, not the child! Second, “Envelope” is a unique manual motion where the canal shaping occurs on the outstroke. A curved file is simultaneously withdrawn in a clockwise motion, which then randomly sculpts the canal prep using the shaft of the file. The envelope is the only dental motion that is achieved moving away from the patient vs going toward them.

What is Restraint?
Google defines Restraint as “a measure or condition that keeps someone or something under control or within limits” and “unemotional, dispassionate, or moderate behavior; self-control.” Restraint comes from the 15th-century, Old French word “restreinte,” meaning “a sense of reserve.”

What do we know about the word “restraint,” and how can it make us better at doing endodontics? During the human species’ 300 million years of evolution, the act of restraint was not a useful word for Mother Nature’s survival of the fittest.2 Restraint could get you killed, and that would be the end of your genetic flow. However, 300 million years later, fight or flight often prevents masterful endodontics.

Restraint is not a question of willpower. It is biology.

Restraint is best measured in the endodontic clinician by something that is familiar to us: tactile sense. How do we know we are practicing at the highest tactile sense possible? How do we know where our “Restraint Threshold” is? For some insight into your own perception of “restraint,” I invite you to take the following self-awareness test.

Restraint: A Self-Awareness Test
Take a pen or pencil and hold it vertically between your thumb and index finger. Hold it as lightly as you can without dropping it. Now hold with 5% less squeeze. If it did not fall from your fingers yet, hold with 10% less squeeze. Most dentists do not drop the pen at 5% less squeeze and some go up to 20% or 25% less squeeze before the pen or pencil falls out of their fingers. Some dentists hold on even longer. To start with, for most of you in the test, restraint was somewhere between your light grip of pen holding and your feather grip, where you ultimately lost control and dropped it.

What’s the endodontic point? Every one of us has the capacity to be more delicate, gentle, and nimble in “Following” a canal to its terminus. The benefit of increased restraint for the dentist and the patient is to have more precision, be less invasive (only removing enough and the correct dentin for the radicular prep) and flawless (fewer mistakes, such as blocks and ledges), and to make the procedure more enjoyable since Glidepath mechanics approach effortlessness. The skill of increasing restraint is available to all of us, and, once the awareness is raised, then “Finding,” “Following,” and “Finishing” endodontic treatment and thinking is automatically changed to something like “The more restraint I own, the more delicate I am, and the easier my endodontics becomes. I am actually feeling guilty that my endo is going so easily.”3

Relationship Between Restraint and “Finding” All Canals
Applying the benefit of restraint in “Finding” all canals (ie, not being in a hurry, learning local knowledge, slowing down), all contribute to making endodontic accessing successful. Restraint allows us to savor the singularity of each access. Every access cavity is the only endodontic “cave” of its kind. Of the 7-plus billion humans on this planet, you are the one privileged to design this one-of-a-kind anatomical search. A Restraint in “Finding” the canal orifice is encouraged by accurate bite-wings, 3-D CBCT,, and CEJ landmarks for optimum root canal system access. Do not simply start drilling and expect to find the chamber. Intentionally design the access cavity and take your time to get it right! In a nutshell, treat these tissues with restraint. Remember the pen or pencil dropping. In the test, most of us had more restraint to give or, better yet, give away.

Many dentists still miss the mark with access cavities. No plan is made, and a patient’s tooth is accessed with hope being their guide. So slow down, plan, and display a little restraint. The rewards are big: You “Find” the canal(s), the important retentive ferrule is not affected or destroyed, and you do not perforate! All these results are produced by slowing down and practicing restraint. Most dentists show too little restraint, go too fast, and sabotage their ability to “Find” canals from the very beginning.

Relationship Between Restraint and “Following” Canals
No aspect of endodontic mechanical skills benefits more from restraint than “Following” canals to their termini and maintaining or confirming the produced, smooth Glidepath tunnel. Regardless of disruptive technologies to improve the classic Clean, Shape, and Pack trifecta, the manual ability to “Find” and “Follow” canals emerges as Restraint: The Lost Art of Endodontics. The GentleWave System (Sonendo) promises disinfection, ProTaper Gold (Dentsply Sirona Endodontics) promises minimally invasive precision shaping, and EndoSequence BC Sealer (Brasseler USA) promises a monoblock-type 3-D sealer obturation, but unless the dentist can “Follow” the canal’s orifi to their termini, none of these clean, shape, and pack innovations have any real value. Restraint, however, transforms and transcends today’s emerging technologies.

So how do we use restraint to help us win the endodontic game? During canal “Following,” Restraint is a way of Doing and a way of Thinking. Let’s examine and learn from each.

Restraint and Doing. First, know the canal is there. You do not have to find it. Slipping and sliding down the canal is easy if we do it right. Start with a 21.0-mm .06 file or a .08 file with a double curved shaft (Figures 1a to 1d). Multiple subtle curves enable the file to “Follow” randomly down Nature’s canal by careening off curving walls (Figures 1e to 1h). Irrigate with Chlor-XTRA (Vista Dental Products); this solution contains a surfactant to help penetrate and more rapidly dissolve any remaining pulpal tissue. Once the tip of the file is directed into the canal orifice, stop directing it. “Follow” the existing path by apically stroking and sliding down the handle of the file with index finger and thumb until it is short of maximum resistance. A light glove coating of baby powder facilitates the light-pressure finger sliding. The reason to stop attempting to “Follow” down the canal is because of possible danger deeper. The actual resistance is due to 4 possibilities: (1) dentin mud or collagen, (2) the access and incidence of file curvature and the canal itself do not mimic each other, (3) the tip of the file is wider than the width of the canal, or (4) the shaft of the file is starting to bind in its body somewhere short of the tip.4 Situations 1 to 3 require file removal and a change in curvature or size. However, if the shaft is preventing navigating farther down the canal, then the “Envelope of Motion” will solve the situation and allow the file to “Follow” farther toward the chosen length (Figures 1i to 1l). A good word to describe the envelope of motion, the ultimate Lost Art of Endodontics, is the word “carve.”

“Following” is distinguished from the Watch Wind manual technique that most dental students have learned. In Watch Wind, the clinician is directing. This can cause the failure of the file to easily proceed apically. For example, if the clinician Watch Winds to the right and the canal actually goes to the left, the beginning of a shelf can begin. While the manual motion of Balanced Force is useful in expanding an existing smooth-walled Glidepath, it can be a dangerous way to slide down a canal tunnel with walls that are not pristinely smooth.4

The walls of the canal coronal and short of the point of maximum resistance are shaved by simultaneously withdrawing and clockwise carving with the “Following” file. This skill is called the “Envelope of Motion.” After one or several Envelopes, the same file is once again “Followed” as deep into the canal as it can easily “Follow” until it is again short of maximum resistance then the “Envelope of Motion” is repeated one or several times. This sequence continues until the desired length is achieved (Figures 2a to 2k). If, after any given Envelope, the file does not “Follow” deeper, do not push or “try” to go deeper because restrictive dentin is not the situation any longer. The situation is, as noted above, either dentin mud/collagen, the file curve is wrong or lost, or the file is too large at the tip. In order to solve these 3 situations, remove the file and place the new curve and also perhaps choose a smaller diameter file. If no force has been used, it is unlikely dentin mud or collagen is piled up ahead of the file. Slide the now differently curved file down the canal and repeat the above sequence until length is achieved. Then proceed as desired toward the Finishing Glidepath (Figure 2l).

Restraint and Way of Thinking. Restraint is intentional by deciding before and literally at every second during the “Following” skill to relax; to be gentle, patient, thoughtful, present, and nimble; and to have positive expectations. Remember, we have to overcome 300 million years of evolution insisting on fight or flight for the survival of the fittest. We are genetically programed to move into flight or fight whenever something resists us, is in our way, or prevents us from getting what we want. Don’t feel bad that you pushed the file and blocked or ledged. We are built that way. All you have to do is be aware of restraint, and your canal “Following” success will follow. We want to reach the end of the canal. The only problem is that fighting the canal back in by “trying” to go deeper becomes counterproductive and eventually results in a dentin mud/collagen block or a canal wall ledge that is difficult or impossible to bypass. If nothing else, think: What do I want to do with this file, how will I know I have achieved my goal, and what do I need to do differently if I don’t? Restraint is usually the missing component. Some clinicians just start filing for a while and hope something good will happen. It rarely does!

The purpose of this article is to increase the awareness of the value that restraint plays in the endodontic mechanics of “Finding, Following, and Finishing.” The more mature I have become in my own personal practice of endodontics, the more I experience that restraint allows me to prepare a successful Glidepath in extremely narrow and apically curved canals. The transforming magic of restraint is available to all clinicians. Now it’s your turn!


  1. West JD. Manual versus mechanical endodontic glidepath. Dent Today. 2011 Jan;30(1):136, 138, 140.
  2. Harari YN. Sapiens; A Brief History of Humankind. Harper, 2017.
  3. West JD. The three F’s of predictable endodontics: Finding, following, and finishing. Dent Today. 2016: 35(3):90-96.
  4. West JD. The endodontic glidepath: Secret to rotary safety. Dent Today. 2010;29(9):86-93.

Dr. West received his DDS from the University of Washington, where he is an affiliate professor. He is the founder and director of the Center for Endodontics in Tacoma, Wash, and a clinical instructor at Boston University, where he earned his MSD and was honored with the Distinguished Alumni Award. Dr. West and his 2 sons, Drs. Jason and Jordan West, are in private endodontic practice in Tacoma. He can be reached via email at

Disclosure: Dr. West is co-inventor of ProTaper Gold, WaveOne Gold, and Calamus Technologies.

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