Cents and sensibility

X-ray taken by Dr. HB Johnson circa 1939 (courtesy Dr. Tom McDonald, Atlanta GA)

X-ray taken by Dr. HB Johnson circa 1939 (courtesy Dr. Tom McDonald, Atlanta GA)

When preparing a root canal, there seems to be nothing that can’t be achieved by a skilled endodontist. In the right hands, virtually any root canal can be prepared with virtually any file or number of files. The very small curvature radius and large curvature angle in the featured x-ray illustrates the extraordinary skill for using carbon steel files in 1939 by Dr. H.B. Johnson, the individual that gave us the term “endodontics.”

Curiously, it is rare that a file is promoted today without an accompanying x-ray depicting an extraordinarily difficult case. Should we conclude then that all files will enable you to achieve ideal root canal preparations? We can eliminate almost all restrictions except for one, our inability to freeze time. Ahh… there’s the rub. Time is our most valuable commodity.

Many years ago, a clever sales rep showed me a time saving formula demonstrating the annual money savings that a very expensive digital x-ray device would provide before convincing me to buy what turned out to be the very first digital x-ray device sold in the US. Ever since, that formula has continuously convinced me that penny-pinching at the expense of saving time isn’t really saving money at all. It’s no different with endodontic files. Consider that by saving 10 minutes/patient with each of 6 cases/day for 200 days results in 5 weeks of chair time saved annually. That’s more than a month of additional production, vacation or whatever you like!

A file’s ability is not the issue. Rather, a file’s efficiency during performance is THE most important issues and our guiding objectives when designing NanoEndo files. Our results are extremely successful in this regard and our customers agree that NanoEndo’s highly efficient designs save them time and reduce risks during root canal preparations. See for yourself and review our comparisons with the files you are using now or give us a call (844.ONE.FILE) to learn more. Remember lost time can never found.

Is scientific hype replacing scientific evidence?



**Watch this VIDEO to see a brief summary on how results from our testing of file performance differs from conventional testing of flexibility and cyclic fatigue.**

Many endodontists have devoted a great amount of valuable time to endodontic instrumentation research using scientific evidence in an attempt to convey useful information for the advancement of endodontics. Scientific evidence relies on comprehensive data and it is crucial for researchers to ensure that the data they collect is sufficiently inclusive to have relevance to actual clinical situations. When “scientific hype” reaches the point that it diminishes the value of scientific evidence, then practitioners need to be aware that insufficient information can have counterproductive consequences.

During scientific research it is not uncommon to encounter hype. Although somewhat frustrating, common hype is usually tolerated because claims are at least somewhat true. Even though the benefits of the claims are usually exaggerated, they are transparently limited in scope. An example of such a claim would be: “These files are faster, safer, and require fewer sizes.”

What is apparent to the dentist is the missing ‘compared to what’ or ‘under what circumstances’. Taken alone, these claims are obviously discounted as scientific evidence. Recently, however, a more insidious hype, one that uses insufficient and selective scientific testing, has lead to erroneous conclusions and created an opportunity for mistakes. This type of hype uses the convincing nature of inductive reasoning that is not so apparent, but may be easier to recognize once it’s broken down into logical propositions. Consider the following examples:

From a specific proposition such as:
A file’s greater resistance to cyclic fatigue is better than less resistance to cyclic fatigue.

To a general proposition:
Greatest resistance to cyclic fatigue results in the best file.

This particular general proposition has gained widespread acceptance and success in the promotion of endo files. One company claims, “700% greater fracture resistance compared to traditional NiTi files” without stating that the increased resistance to cyclic fatigue was accompanied by a reduction in the resistance to torsional stress, an essential component of resistance to failure. Another company uses resistance to cyclic fatigue as evidence for “unmatched strength”, “Off the charts Strength,” “Amazing strength means the confidence…,” and “Twice the strength, half the cost.”

The definition of strength within the context of metallurgy is the resistance to deformation. Now consider that the files described above distort with the least force of almost all, if not all, of the files on the market. All other factors being equal, increasing the resistance to cyclic fatigue is concurrent with a decrease in file strength and resistance to torsional stress. Unwinding is evidence of torsional stress. The question becomes, as long as the resistance to cyclic fatigue is adequate, why compromise by reducing the resistance to torsional failure?EdgeVsOneEndo_Graphs

There are certain features of science that give it a distinctive character as a mode of inquiry. Once that mode of inquiry is compromised, It is no longer valid science. When a company claims that its file will rotate over 600 seconds in a 90 degree curvature 3mm from its tip, and that capability is two times as long as a competitive file, does it make it a better file? If it does, does that mean a copper wire of the same diameter that will rotate 1,800 seconds is the better file? Actually, it only means that it has better resistance to cyclic fatigue in that particular circumstance with no evidence for superior performance. Besides, who lets a file rotate 600 seconds in a 90 degree curvature? Or even 10 seconds? Is there relevance to actual clinical situations?!

The ultimate goal for instrumentation advancement can be stated as, ‘maximizing efficiency and minimizing risks while accomplishing the preferred results.’ How effectively that goal is achieved is a measure of performance. My hope is that you will scrutinize all claims of advancement to the best of your ability. That especially pertains to any claims that I might make. Scrutiny is the hallmark of advancement.


Conventional Research: Greater Value than Actuality?

Screen Shot 2015-11-09 at 9.08.49 AMAfter so many years of research, it is daunting to succumb to the realization that so much of my time was devoted to compiling conventional, or what could be considered useless, data for evaluating endodontic files. Someone once commented, “There is no ox so dumb as the orthodox.”

For instance let’s consider a file that is statically in the 50 percentile compared to other files in resistance to cyclic fatigue and also in the 50 percentile (50/50) in resistance to torsional failure. Research will reveal that files that are in the same percentiles can perform very differently. Compiled data for these percentiles might give little indication as to how a 60/40 percentile would perform  or a 40/60 percentile. Certainly a 100/? percentile can amount to little more than hype. There are too many other design differences to consider for extrapolating for conclusions.

My realization from the research I have experienced is, file features should only be considered file features with no indication of how the file will perform until performance itself is measured. Only then, should we attempt to explain the performance in terms of the file’s features. We can use the “ox“ depiction again to represent the paradox of Schrodinger’s cat; we have to see the results first to explain them and then our explanations might actually be very comprehensive.

Fortunately, we at NanoEndo have conducted literally 100s of file evaluations measuring performance, probably more than all other performance evaluations put together. And, fortunately, you do not have to depend on projections. NanoEndo files speak for themselves; their performance excels beyond comparison. We invite you to see for yourself.

Exo Endo : Tip Evaluation (1st 3mm)

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WEBSITE: NanoEndo.com



SIZE: 25/04
FLUTES: 3; changes to 4
HELIX ANGLE: 9º (25º at handle end) [fig. 2]
CUTTING ANGLE: (-)33º [fig. 1]
60 ̊ DEFLECTION: 7.4 g



  • The EXO ends file is comparatively favorable for rotation to failure and peak torque at failure.

    Tip SEM

    Tip SEM

    Fig. 1

    Fig. 1

    Fig. 2

    Fig. 2








    SEMs are provided by Dr. Franklin Garcia-Godoy, Professor and Senior Executive Associate Dean for Research Director, Bioscience Research Center University of Tennessee Health Science Center


Direct comparisons of a singular NiTi file design with and without heat treatment


The physical properties of nickel titanium endodontic files that are heat treated for enhancing flexibility differ so widely that definite correlations are difficult to determine. This is particularly true when there are no controls for heat treated files having the same design dimensions. D&S Dental, LLC provided identical files having different degrees of heat treatment for testing and determining correlations. One group of files had no heat treatment (Group A), one group had medium heat treatment (Group B) and one group had greatest heat treatment (Group C). Each group was tested for rotation until failure (suspended at 3mm from tip), peak torque at failure, and force required for 5mm deflection on a 60 degree inclined plane to measure tip flexibility. Group A, no treatment, values were used as base lines for comparisons.The results are as follows:


Group B Group C
Degrees Rotation to Failure (+)61% (+)33%
Peak Torque at Failure (-)7.6% (-)69%
Force on 60 Degree Incline (-)12.5% (-)26.6%


Although there is an approximate direct correlation for peak torque at failure and force for 60 degree incline flexibility, the degree of rotation to failure appears to be an aberration of expectation. Within the scope of this limited research, we can conclude that heat treatment applied to enhance flexibility will accompany a decrease in resistance in torsional stress.

NanoEndo and Stellar Studios Awarded Gold Communicator Award for nanoendo.com

NanoEndo is proud to announce its website, nanoendo.com, has been awarded a Gold Communicator Award from The Academy of Interactive and Visual Arts. The website was developed in conjuction with Stellar Studios, a multimedia marketing agency based in Johnson City, TN. The Gold Communicator Award falls within the Websites, Websites Visual Appeal category and recognizes nanoendo.com for its unique design characteristics and overall esthetic appeal.

“We really wanted to create something different that stands out from our competitors. My father and business partner, Dr. McSpadden, is distinguished as one of the world’s foremost endodontic file designers and he considers the One Endo file to be the best overall file design he’s ever seen. When we founded NanoEndo LLC to bring the One Endo file to market, I knew that our website would become the cornerstone of our efforts and I wanted its design to highlight the same uniqueness in thought and attention to detail evident in my dad’s instrument design. I have a long history of working with Stellar Studios to create award winning multimedia designs and it was a forgone conclusion that they would help us achieve our goals. Stellar Studios is an outstanding agency with tremendous talent and we are very fortunate to count them among our friends and partners.” – JT McSpadden, Chief Operating Officer, NanoEndo LLC

The Communicator Awards is the leading international awards program recognizing big ideas in marketing and communications. Founded two decades ago, The Communicator Awards receives over 6,000 entries from companies and agencies of all sizes, making it one of the largest awards of its kind in the world. The Communicator Awards is sanctioned and judged by the Academy of Interactive & Visual Arts, an invitation-only group consisting of top-tier professionals from acclaimed media, communications, advertising, creative and marketing firms. AIVA members include executives from organizations such as Airtype Studio, Big Spaceship, Conde Nast, Coach, Disney, The Ellen Degeneres Show, Estee Lauder, Fry Hammond Barr, Lockheed Martin, MTV Networks, Pitney Bowes, rabble+rouser, Sotheby’s Institute of Art, Time, Inc, Victoria’s Secret, Wired, and Yahoo!


On Communication and Collaboration for Advancing Endodontic File Design

While the overwhelming majority of comments we receive regarding our research and innovations is very positive and complementary, publishing our independent research while marketing our own endodontic file designs and claiming unbiased objectivity opens us up to criticism and scrutiny. We expect and welcome such skepticism as it inspires discussion and informs further investigations. Our hope is that our openness to criticism and our transparency in operations will ultimately serve to balance biases and provide an open dialogue wherein all perspectives may be granted equal consideration. To that end, please consider the following comments we’ve received regarding our most recent series of endo file evaluations alongside our responses to them:

Alex’s Comment: (background unknown)

Great job Dr. McSapdden! Your experiment’s design proved that your file is the best! Well done!! Now it’s time to put together an experiment to prove that your children are the cutest!! Come on man! Is this a joke? How can you sell a file and test competitor files? Well. Thanks for wasting my time reading this commercial.

Dr. McSpadden’s Response:

The instant formula for failure may be to try to please everyone but we try. We try by using equipment that can give results that can be consistently replicated independent of the operator. We try with a commitment to publishing the results without knowing in advance what the results will be. We try by inviting any change in the parameters we use for testing as well as inviting anyone to observe the results as they occur. We try by including 35 years of our past testing experience to provide the most useful information we know how. We try by using the information we have accumulated to design instruments that might help in providing solutions for clinical needs. We try by having our quest for solutions to be a continuing endeavor. We try by convincing ourselves that trying is better than doing nothing when success is unknown but that even failure might be at least some benefit. And, we will try to help you find solutions if you should ask and hope that you might try to do the same for us. And, yes my grandchildren are the cutest and, as a 75 year old grandfather who doesn’t need to sell files, I will admit that particular claim might be biased.

David Clement’s Comment: (UTHSC Grad Endo)

This is a great project you are sharing with the Endo Community.  I look forward to seeing further results which you say will be distributed regularly. Just one comment, and perhaps a description criteria you could consider adding to the Descriptive Characteristics. The Circular core dimension as a percentage of the circumferential size (diameter) would be a very interesting characteristic to see.  The bulk of metal in the core (Not including the exposed cutting edges) could give fundamental information/understanding on torsional strength and and Cyclic fatigue characteristics of these rotary files.  It would also give information is the core area changes in the length of the blade, theoretically increasing the Flute space ( debris removing area). Again, Many thanks for sharing the project information with us. 

Dr. McSpadden’s Response:

…I think your idea is excellent. It might be good to carry it a step further and have the core as a percent of the total x-sectional area. If we cannot change the program easily I can include it in the discussion. I really appreciate your interest and comments.

If you have any questions or comments of your own, please feel free to share them with us however you like. Post them here, send us an email or give us call (844) ONE-FILE [663-3453]. We value your input and perspective and hope you will help us in collaborating for the advancement of endodontics.

One Endo : Tip Evaluation (1st 3mm)


WEBSITE: nanoendo.com



SIZE: 25/04
FLUTES: 2 (S-shape, H-type)
HELIX ANGLE: 7.5º [fig. 2]
CUTTING ANGLE: (-) 40º [fig. 1]
60 ̊ DEFLECTION: 3.56 g



  • The degree rotation to failure is less than that for the Edge file or the ESX.
  • The peak torque at failure is more than the Edge but less than the ESX.
  • Interestingly, the One Endo was not superior in either the rotation to failure or deflection tests but was the only file that did not fail the Endo File Evaluator protocol. This is likely due to the One Endo’s blade that extends closer to its actual tip and the single blade opposed by a rounded surface and its reduced helix angle. These features facilitate greater efficiency in debris removal.




Fig. 2











Descriptions of Protocols and Terminology

Rake & Cutting Angle:
If the file is sectioned perpendicular to its long axis, the rake angle (cutting angle) is the angle formed by the leading edge and the radius of the file inscribed in its circle of rotation. While using the radius as the line of reference, if the leading edge is in front of the perpendicular radius, it is referred to as a negative (scraping) cutting angle and is measured as the angle formed by the leading edge and radius. If the leading edge is behind the radius, it is referred to as a positive cutting angle.

Negative Angle

X-Section with Negative Angle

X-Section with Positive Angle

X-Section with Positive Angle









Circumference Area & Core Area:
The circumference area (A=3.14r²), inscribed by the rotation a file, is determined by defining r as the distance from the file’s central axis of rotation to the file’s outer most boundary. The core area of the file (A=3.14r²) is the cylindrical center area of the file having its circumference outlined and bordered by the depth of its flutes. It should be noted that there are instances when the central axis of rotation is separate from the file core’s center.

File with symmetrical X-section

File with Symmetrical X-Section

File with Asymmetrical X-Section

File with Asymmetrical X-Section









The flute of the file is the groove in the working surface used to collect soft tissue and dentine chips removed from the wall of the canal. The surface having the greatest diameter that follows the groove (defined as where the flutes intersect), as it rotates, forms the leading (cutting) edge. The number of spirals that a file has in its working surface can be calculated by dividing the number of flutes on the working surface by the number of flutes in  x-section.

Sides of X-Section Point to Corresponding Flutes

Sides of X-Section Point to Corresponding Flutes











The helix angle is the angle the blade makes as it intersects with central longitudinal axis of the file.

Helix Angle

Helix Angle






The debris removing area is the total flute space represented as a percentage of the circle area that inscribes the file.







Deflection is measured as the file is lowered 5mm onto a 60 degree incline. If the file remains bent as it is lifted from the incline, the angle of the bend is measured as plastic deformation.










To determine rotation to failure, 3mm of the tip end of a file is locked into place before rotating its handle end continuously until it breaks. The degree of total rotation is measured at the point where the file fails.


Peak torque at failure describes the maximum torque the file undergoes as it is rotated to failure.




Introduction to Mastering Endodontic Instrumentation : An online addendum

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What differences do design differences make? We intend to find out. We are embarking on a very ambitious research program to test each part of every major file in production, from tip to handle. We have completely up-dated the computer controlled Endo File Evaluator to improve resolution of its sensors and motors and to expand its capability for performing new testing protocols. As such, we have created what I believe is not only the most objective means for evaluating endodontic files, but also the best method for testing file functions in a manner that is truly relevant within a clinical setting. We do this while letting the data determine the results for objective comparisons independent of operator skill or marketing bias.

What difference does this endeavor make? Our first objective is to finally determine how to minimize risk and maximize efficiency, how file designs relate to function, how function relates to canal anatomy, and how anatomy relates to technique. Our second objective is to present the Endo File Evaluator results using the numerous different parameters for testing, and to use high resolution images and SEMs in a manner that allows clinicians to save and apply the information to enhance their skill and treatment.

How will this process take place? About every ten days we will share test results and observations of only one segment of each file beginning with the file tips. Through this blog, we invite you to participate in discussions and critiques to create group research dynamics as this project progresses. Once all segments of the files have been covered, a composite of each whole file will be available as an endodontic reference along  with any contributing assessments gathered from our readers. We will continue providing results as we find them through this comprehensive series of evaluations and add to them in the future as needed. We are excited to embark on this endeavor and hope you will follow along and contribute your own thoughts and impressions.