Is scientific hype replacing scientific evidence?

EdgeVsOneEndo_Pics

 

**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.

 

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)

DETAILS:

FILE NAME: One Endo
COMPANY: NanoEndo
MANUFACTURER: D&S Dental
MADE IN: USA
WEBSITE: nanoendo.com

 

CHARACTERISTICS:

SIZE: 25/04
FLUTES: 2 (S-shape, H-type)
SPIRALS PER 16MM: 3.5
HELIX ANGLE: 7.5º [fig. 2]
CUTTING ANGLE: (-) 40º [fig. 1]
DEBRIS REMOVING AREA: 38% [fig. 1]
ROTATION TO FAILURE: 510º
PEAK TORQUE AT FAILURE: 86.81 gf/cm
60 ̊ DEFLECTION: 3.56 g
PLASTIC DEFORMATION: 0º
FILE CORE AREA RELATIVE TO CIRCUMFERENCE AREA: 43%
FILE CORE AREA RELATIVE TO FILE X-SECTION AREA: 65%

 

DISCUSSION:

  • 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.

 

TIP SEM

Fig. 1 : TIP X-SECTION

Fig. 2

 

 

 

 

 

 

 

 

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Stacking the Deck : A response to questions about our selection of testing protocols

CardCheat

Recently, we received feedback regarding our methodology for creating protocols for evaluating endo file performance on our Endo File Evaluator, a computer controlled clinical simulator. As always, we encourage your participation in our discussions and we felt others might benefit from including these comments in our public forum. The comment submitted through our website contact form is as follows:

“I’ve been looking over some of your data comparison in regards to your Evaluator V2 and am borderline appalled at how misleading it is and how you’ve set your file system up to succeed in that scenario and make sure that others do not perform. You have all 11 file systems in that Evaluator V2 running at 550rpm [sic] knowing good and well that for several of the file systems on there 550rpm is much higher than the recommended speeds Many of those systems run at 300rpm. Not to mention the torque you are using in the settings is also much higher than normal for many of the files. I find it to be quite a coincidence that the speed you choose to do the Evaluator V2 test comparisons at is the exact optimal speed of your own file. It seems to me that without testing each of these systems at their optimal speed torque technique your are doing nothing more than publishing skewed results that have been made to lean in your direction.”

Were this in fact the case, we also would be appalled. Distinguishing hype from fact was precisely the reason Dr. McSpadden developed his Endo File Evaluator. The protocol mentioned and its use of 500 rpm and unlimited torque setting is actually arbitrary and was intended to establish a baseline for future comparisons. Our goal with protocols is primarily to find the limitations that dictate optimum performance. The first series of protocols takes various file sizes to a canal’s apex with a particular speed and rate of insertion with no regard for the file’s size relative to the canal opening. This is not a technique we, or I dare say anyone else, would ever recommend using in their practice.

Rather, our methodology allows for direct comparison of torque and pressure readings that may be viewed in a graphic format and ensures a level playing field for interpreting the data. Previous testing performed on the V1 Evaluator used several various protocols with multiple rotation speeds and insertion rates. This data informed Dr. McSpadden as he wrote Mastering Endodontic Instrumentation and ultimately inspired his design of the One Endo file. It has always been our intent to continue our testing and comparative analyses of endo files using an ever broadening scope of protocols. To that point, we  are currently completing a full evaluation of most endodontic file designs in an ongoing series that we will share as a new blog scheduled to launch next week.

Furthermore, from our beginning, we have invited anyone to Request-A-Test on our Endo File Evaluator. Through this online form, anyone may submit ideas for additional protocols they wish to see performed on our Endo File Evaluator and we will be happy to perform them and publish the results, even if they prove unfavorable to our own designs. Our mission is to empower endodontic practitioners and advance their potential by offering the most effective products while providing open access to unbiased informational resources for instrumentation and design. What we seek is knowledge and what we hope for is your participation.

The Emperor’s Clothes; Making the Invisible Visible

emporer

The ability to provide unparalleled critical information about teeth and their surrounding tissues has been transformed with the development of 3-D imaging systems such as Cone Beam Computed Tomography. Our knowledge is no longer limited to conventional intra-oral radiographs that represent a two-dimensional view of three-dimensional anatomic structures. Our two-dimensional interpretations can now be replaced with a vast array of three-dimensional data that are more apparent and more applicable for statistical analyses.

We might say that the testing of endodontic files is undergoing a comparable transformation. We are no longer limited to two image representations of a file, (1) the image resulting from scientific research encompassing only one feature of a file and (2) the image resulting from claims of marketing, the emperor’s clothes. The clinical simulator used by NanoEndo to compare files has the ability to precisely determine and record the extent of a file’s capabilities under various circumstances and simultaneously assess its efficacy compared to that of other files. This development is an important step towards being able to distinguish between hype and useful information and may radically change the dentist’s ability to evaluate files. NanoEndo aspires to be the one that points out, “But he isn’t wearing anything at all!” and to make a file’s proficiencies apparent and assessable to all. Is it marketing or is a file carrying a $19 price tag that valuable? Is a $4 price tag cheap? We can provide unbiased computerized testing; you can make the judgement.

 

The file is a Sequence EXS 25/04 before testing. The claim: allows for stress free apical progression and clearing of debris while respecting even the most challenging canal anatomy. The patented BT Tip™ features 6 cutting edges, for increased cutting efficiency. This revolutionary design allows for the use of fewer instruments per treatment. Retail price: $19.33 per file.

The file is a Sequence EXS 25/04 before testing. The claim: allows for stress free apical progression and clearing of debris while respecting even the most challenging canal anatomy. The patented BT Tip™ features 6 cutting edges, for increased cutting efficiency. This revolutionary design allows for the use of fewer instruments per treatment. Retail price: $19.33 per file.

 

This is the same Sequence EXS 25/04 shown above after testing (refer to: https://nanoendo.com/evaluator-v2.php). Reason for failure: The claim features 6 cutting edges at its tip but close inspection shows smooth edges until the greatest tip diameter, 0.25mm, is reached. This causes the tip to have to burnish its way into a canal that has a diameter smaller than 0.25mm. The stress causes the tip to unwind. As the tip unwinds debris in the flutes becomes trapped and causes greater stress from abrasion.

This is the same Sequence EXS 25/04 shown above after testing (refer to: Endo File Evaluator). Reason for failure: The claim features 6 cutting edges at its tip but close inspection shows smooth edges until the greatest tip diameter, 0.25mm, is reached. This causes the tip to have to burnish its way into a canal that has a diameter smaller than 0.25mm. The stress causes the tip to unwind. As the tip unwinds debris in the flutes becomes trapped and causes greater stress from abrasion.

The file is a One Endo file after testing (refer to: Endo File Evaluator). Reason for success: Sharp cutting edges extend very close to the actual tip end, yet opposite the cutting edge the tip is smooth enabling it to follow the canal. Retail price: $11.25 per file with frequent discounts.

The file is a One Endo file after testing (refer to: Endo File Evaluator). Reason for success: Sharp cutting edges extend very close to the actual tip end, yet opposite the cutting edge the tip is smooth enabling it to follow the canal. Retail price: $11.25 per file with frequent discounts.

Why different endo files have a different “feel”

The One Endo file's cutting edge extends through its tip.

The One Endo file’s cutting edge extends through its tip allowing it to cut very efficiently. This efficiency, however, may be perceived as having an “aggressive feel”.

Endodontic files basically have three functions: forming a dentinal chip, dislodging the chip, and transporting the chip from an area of file engagement to an area of file disengagement.

A file may have a smooth feel when the blade is burnishing more than cutting, or when the flutes are compacted with debris. Using a “smooth” file usually requires a heavier touch or more pressure for advancement into the canal. Often this feel is confused as an attribute of a more effective file. In fact, the greater pressure required for advancement into the canal causes greater torsion stress that results in a greater propensity for failure compared to more efficient files.

Sharper more efficient files may have a rougher, scratchier feel than that of less efficient files. This is due to the formation of greater dentinal chips. These files require a lighter touch or less pressure for advancement to achieve the same results as less efficient files.

Often when one transitions from using a less efficient file to a more efficient file they have the tendency to use the same force as was required for the less efficient. Greater pressure can result in the formation a larger dentinal chips than can be easily removed and result in unnecessary excessive torsion stress.

Our extensive testing has consistently indicated that applying the following considerations will maximize efficiency and minimize risks:

  • Advance into the canal using no more pressure than was required to advance the first 1mm.
  • Engage no more than 6mm of a file if it is engaged in a curvature (the exception would be a size 20-.02 or smaller).
  • Advance a file into the canal with no more than 1mm increments with insertion/withdrawal motions.
  • Advancement into the canal should be able to occur at a rate of approximately 0.5mm/s without increasing the pressure of insertion.
  • Withdrawing at a rate greater than the rate of insertion improves debris removal.
  • Follow the use of one file with a file having a different taper.

What does progressive flexibility for the One Endo file mean?

Heat treated One Endo files are distinguished by a golden coloration.

In short, progressive flexibility means the flexibility increases as the need for flexibility increases. This is in contrast to the all or nothing approach of other brands. Flexibility of a file can be increased by the following means:

  1. Increase the depth of grooves. However, increasing the depth of flutes can make the instrument more vulnerable to torsional failure, particularly if applied to all file sizes.
  2. Increase the number of spirals. Yet, increasing the number of spirals has two consequences: the file has a greater tendency to screw-in, and debris has a greater distance to travel causing more abrasion and torsional stress.
  3. Apply heat treatment. However, heat treatment usually means decreasing the file’s resistance to torsional stress. Some manufacturers claim that their heat treatment  process actually enhances or has no effect on the file’s resistance to torsion stress. These claims are usually justified by measuring only the number of turns of rotation a file can be twisted before failure without consideration for peak torsion (greatest amount) the file can resist.

For virtually all cases, increasing flexibility decreases a file’s resistance to torsional failure. On the other hand, once the file has adequate resistance to torsional failure due to size, greater cross-sectional mass or flute design, the file’s flexibility can be increased by any or all of the means listed above progressively to enhance the file’s performance. The objective of the One Endo file series is to balance the need for flexibility with the need for torsional resistance. You will notice that One Endo files size 35 and larger are heat treated. The exception is size 35 .04/.06 in which its flexibility is increased by increasing flute depth. File size 55 .04/06 is heat treated to a greater degree to provide the needed flexibility for this large size.

Resistance to Change: What keeps you from leaping ahead?

Are dentists really, as the cliche goes, the most resistant to change? I contend that they change when change is worthwhile. So, what does it take for you to embrace changing endodontic files? Math can affirm that saving just 5 minutes a case can amount to 10-25 days a year of additional income or days off, not to mention the other benefits of efficiency. Even if these savings are validated, resistance to change could be influenced by many factors. Let’s consider some of the usual suspects:

  • You resist change because you feel you will not be able to make the transition easily.
    • Changing the instruments you use on a daily basis is a daunting prospect, especially when it means having to change your technique. While there are basic considerations to address within any technique to maximize its effectiveness, the One Endo File can be used with ANY technique to achieve better results. Also, It can even be used with a reciprocating handpeice as long as its clockwise angle of rotation is greater than that of its counterclockwise rotation. Objection over-ruled?
  • You resist change because you feel you have insufficient information.
    • NanoEndo provides you the opportunity to view side-by-side testing to measure the efficacy, efficiency and stresses of the file you are using with a comparable One Endo file. This is accomplished by using a computerized clinical simulator with precise prescribed movements. Objection over-ruled?
  • You resist change because you feel you believe the current way of doing things works well.
    • I have always identified with a quote from Henry Ford who said, “If I’d asked people what they wanted, they would have told me – faster horses.” Subscribing to the idea that well enough is good enough guarantees that your development and attitude will stagnate. Only with change can you enjoy the benefits of expertise while realizing your full potential. Objection over-ruled?
  • You resist change because you are too invested in inventory.
    • Can you justify investing in new inventory when you already have old inventory? Progress always pays off. We are providing the opportunity to buy what is arguably the best endo file available at half price with no limits on quantity. This price-benefit of the One Endo file is without equal in the market place. But the clock is ticking, and at the end of this year we will end what we think is the best deal around: every time you order a pack, we’ll ship you another for free – plus free shipping on all orders! Objection over-ruled

Remember the quote from Churchill, “To improve is to change; to be perfect is to change often.” Our goal is perfection; the next step is yours. We look forward to serving you. Visit the NanoEndo Store.

Does the quality of manufacturing make much difference for endo files?

SEM courtesy Nova Southeastern University College of Dental Medicine

Before different types of files are studied, it should be stressed that the quality of manufacturing is the most basic consideration for determining the success or failure of endodontic files independent of their composition or design. Less than ideal manufacturing quality controls result in the formation of micro-cracks and defects along the surface of a file. Cracks can propagate to failure at a stress level lower than the stress ordinarily encountered during instrumentation and other defects can cause stress concentration points that lead to file failure and jeopardize endodontic success. It should be noted; considerably less force is required to propagate a crack than is required to form it. If the defects are in a position of high stress, failure can occur quickly. The area of highest stress is along the blade or leading edge. The formation of micro-cracks shown on the file’s cutting edge indicated by the arrow is an area for potential failure.

Steps of Endodontic Instrumentation Technique

Many endodontists have spent a great deal of time deciding on the file sequence that serves them best and would prefer not to have to learn a new technique. For those, we would recommend no technique change since the One Endo file was designed to give better results with any technique simply by using One Endo files approximating the sizes of the files of your technique.

On the other hand, we have had requests for specific technique recommendations of how we would recommend the One Endo file should be used. Practitioners should keep in mind the purpose of any recommendation is to provide a means for maximizing efficiency for enlarging the canal space while minimizing instrument failure—not to advocate a particular canal size or taper.The final canal dimensions should be adjusted to conform to the judgment of the operator and the requirements of the obturation technique used.

1 – No Change:

The One Endo file was designed to be used without changing the operator’s preferred technique. The fact is, if the One Endo file performs better than other files of the same approximate size, they can be used exactly in the same way  and achieve better results.

2 – Same Technique with added Parameters:

This step requires no technique change but does make the following recommendations during the procedure:

•Advance into the canal using no more pressure than was required to advance the first 1mm. If more pressure is required, change files.
•Engage no more than 6mm of a file if it is engaged in a curvature (the exception would be a size 20-.02 or smaller). If engagement is greater than 6mm, change files.
•Advance a file into the canal with no more than 1mm increments with insertion/withdrawal motions.
•Advancement into the canal should be able to occur at a rate of approximately 0.5mm/s without increasing the pressure of insertion.
•Withdrawing at a rate greater than the rate of insertion improves debris removal.
•Follow the use of one file with a file having a different taper.

Even though more files may be used in following these parameters, the total cumulative time can be less when compared to other techniques. Each step of instrumentation can occur quickly without repetitive non-productive attempts.

3 – Technique Change:

We recommend a technique change to incorporate the findings of our research to maximize efficiency while avoiding probable risks. We refer to this technique as the zone technique in which we divide the canal into two zones, the coronal zone or the portion of the canal coronal to a curvature, and the apical zone or the portion of the canal apical to a curvature.The zone technique was designed with two objectives for minimizing file stress: One, the canal diameter should be large enough coronal to a curvature to prevent any stress due to engagement in that portion of the canal when any file is being used apical to the curvature. Two, the file diameter is not too large to rotate safely in a curvature; the file diameter is sufficiently small in a curvature to avoid excessive cyclic stress.

ZoneExamples

The first step is to determine if there is a curvature of any significance and how far the curvature is from the apex. Withdrawing the file used to establish the working length, and passively re-inserting will indicate a curvature if it meets any resistance short of the working length since the canal is now larger than the file. The canal portion short of the resistance defines the coronal zone and the portion beyond the resistance defines the apical zone. The length of the canal to the curvature, the coronal zone, is measured and recorded with the same importance as determining the working length. The working length minus the coronal zone length provides the distance the curvature is from the apex, the apical zone length.

The second step is to determine the distance each of the files having different sizes and tapers can safely be advanced around the curvatures and which size file will need to be used in the coronal zone to prevent any subsequent file from binding in the apical zone. At the point of curvature in the, the file diameter should be no greater than .60mm for a .02 taper, .55mm for .04 taper, .50mm for .06 taper, and .35mm for a .08 taper. (This consideration is the result of testing for 45-degree curvatures having 8 mm radii and applies only to these dimensions for rotary NiTi files. File diameters should be smaller for more severe curvatures and can be adjusted larger for less severe ones.) By using the parameters suggested above for diameter limitations, we can calculate if the diameter of a selected file would exceed our limitations.

Example: If the point of curvature is 6mm from the working length and we are considering using a .25/.06 file. The parameters above state that a .06 tapered file should not have a diameter greater than .50mm at the point of curvature and that diameter for a .25/.06 file is at 4mm from its tip. Therefore, in this situation the .25/.06 should only be advanced 4mm into the apical zone and if it is carried to that point, the terminus of the coronal zone should previously be prepared to a size .50mm. Following this procedure at first may seem complicated but it can be learned quickly. The result is a very expeditious and relatively worry free of threat of breakage.