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?

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.

 

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.

Twisted File : Tip Evaluation (1st 3mm)

DETAILS:

FILE NAME: Twisted File
COMPANY: Kerr Sybron
MANUFACTURER: Kerr Sybron
MADE IN: USA
WEBSITE: kerrdental.eu.com

 

CHARACTERISTICS:

SIZE: 25/04
FLUTES: 3
SPIRALS PER 16MM: 4
HELIX ANGLE: 10º (at apical 1/3) [fig. 2]
CUTTING ANGLE: (-)30º [fig. 1]
DEBRIS REMOVING AREA: 55% [fig. 1]
ROTATION TO FAILURE: 805º
PEAK TORQUE AT FAILURE: 15.3 gf/cm
60 ̊ DEFLECTION: 1.42 g
PLASTIC DEFORMATION: 0º
FILE CORE AREA RELATIVE TO CIRCUMFERENCE AREA: 28%
FILE CORE AREA RELATIVE TO FILE X-SECTION AREA: 62%

 

DISCUSSION:

  • Unlike other files tested, the TF files are ground parallel to its long axis, along the length of its working surface. Other files are ground more perpendicular to their long axis during which the microscopic ground grooves form micro cracks that are concurrent with the cleavage planes of the metal. This significantly increases the file’s resistance to torsional failure, not to be confused with stress resistance, during performance.

    Tip SEM

    Fig. 1

    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

     

GT Series-X : Tip Evaluation (1st 3mm)

DETAILS:

FILE NAME: GT Series-X
COMPANY: Dentsply Tulsa Dental
MANUFACTURER: Dentsply Tulsa Dental
MADE IN: USA
WEBSITE: tulsadentalspecialties.com

 

CHARACTERISTICS:

SIZE: 20/04
FLUTES: 3
SPIRALS PER 16MM: 3.3
HELIX ANGLE: 14º [fig. 2]
CUTTING ANGLE: (-)30º [fig. 1]
DEBRIS REMOVING AREA: 22% [fig. 1]
ROTATION TO FAILURE: 470º
PEAK TORQUE AT FAILURE: 4.76 gf/cm
60 ̊ DEFLECTION: 1.42 g
PLASTIC DEFORMATION: 0º
FILE CORE AREA RELATIVE TO CIRCUMFERENCE AREA: 56%
FILE CORE AREA RELATIVE TO FILE X-SECTION AREA: 72%

 

DISCUSSION:

  • The M-wire obviously makes a difference in enhancing its rotation
    to failure considering the file’s large x-section area relative to its circumference. However, this enhancement was accompanied with a diminished resistance to torsional failure.

    Tip SEM

    Fig. 1

    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

     

ProTaper Universal : Tip Evaluation (1st 3mm)

DETAILS:

FILE NAME: ProTaper Universal
COMPANY: Dentsply Tulsa Dental
MANUFACTURER: Dentsply Tulsa Dental
MADE IN: USA
WEBSITE: tulsadentalspecialties.com

 

CHARACTERISTICS:

SIZE: X2
FLUTES: 3 (convex)
SPIRALS PER 16MM: 3
HELIX ANGLE: 20º [fig. 2]
CUTTING ANGLE: (-)31º [fig. 1]
DEBRIS REMOVING AREA: 35.8% [fig. 1]
ROTATION TO FAILURE: 358º
PEAK TORQUE AT FAILURE: 11 gf/cm
60 ̊ DEFLECTION: 1.42 g
PLASTIC DEFORMATION: 0º
FILE CORE AREA RELATIVE TO CIRCUMFERENCE AREA: 54%
FILE CORE AREA RELATIVE TO FILE X-SECTION AREA: 83%

 

DISCUSSION:

  • The resistance to torsional failure was relatively high compared to triangular x-sections. This is due to the greater x-sectional area of convex flutes. The cutting angle is less aggressive and requires greater torsion during performance.

    Tip SEM

    Fig. 1

    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

     

What difference does unwinding an endodontic file make if it doesn’t break?

extrusion segI was recently asked why would it matter if an endodontic file unwound as long as it didn’t break. First, let us think of a file as not only an instrument that enlarges a canal but one that acts as an auger as well; it conveys debris. When a file unwinds to the extent that its helix augers apically rather than in a coronal direction (as in segment 1), then debris is extruded through the apical foramen. Note that part of the file becomes denuded. Post operative pain will most likely be the consequence. The unwound segment 2 continues to auger debris in a coronal direction while the unwound segment 3 augers in an apical direction. The result is compression of debris, additional torsional stress and a greater propensity for breakage. Keep in mind most files will not even unwind 2 revolutions without fracturing. If the file is rotating 500rpm, 2 revolutions require less than 1/4 second before failure.

The short answer to the question is: it probably matters. Luck is not nearly as predictable as cause and effect.

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.

EdgeEndo : Tip Evaluation (1st 3mm)

Screen Shot 2015-02-27 at 10.10.03 AM

DETAILS:

FILE NAME: EdgeFile
COMPANY: EdgeEndo
MANUFACTURER: MicroMega
MADE IN: France
HEAT TREATED IN: United States by US Endo
WEBSITE: edgeendo.com

 

CHARACTERISTICS:

SIZE: 25/04
FLUTES: 3 (triangular)
SPIRALS PER 16MM: 6
HELIX ANGLE: 26º [fig. 2]
CUTTING ANGLE: (-) 40º [fig. 1]
DEBRIS REMOVING AREA: 60% [fig. 1]
ROTATION TO FAILURE: 1002º
PEAK TORQUE AT FAILURE: 51.13 gf/cm
60 ̊ DEFLECTION: 1.62 g
PLASTIC DEFORMATION: 7º
FILE CORE AREA RELATIVE TO CIRCUMFERENCE AREA: 32%
FILE CORE AREA RELATIVE TO FILE X-SECTION AREA: 60%

 

DISCUSSION:

  • Although the file is very flexible, its resistance to torsional stress is very limited. Plastic deformation occurs with comparatively minimal force.
  • The tip is blunt and will not negotiate a canal having a smaller diameter without burnishing its way into the canal and resulting in greater torsional stress.
  • The large number of spirals requires debris to be conveyed a greater distance and increases the EdgeEndo’s tendency to screw into the canal. Both factors contribute to increasing torsional stress.

 

TIP SEM

Fig. 1 : TIP X-SECTION

Fig. 2

 

 

 

 

 

 

 

 

POST A COMMENT

DOWNLOAD PRINTABLE PDF

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

 

 

 

 

 

 

 

 

POST A COMMENT

 DOWNLOAD PRINTABLE PDF