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

Sequence ESX : Tip Evaluation (1st 3mm)

DETAILS:

FILE NAME: Sequence ESX
COMPANY: Brasseler USA
MANUFACTURER: FKG
MADE IN: Switzerland
WEBSITE: brasselerusadental.com

 

CHARACTERISTICS:

SIZE: 25/04
FLUTES: 3 (triangular)
SPIRALS PER 16MM: 2.67
HELIX ANGLE: 9.5º [fig. 2]
CUTTING ANGLE: (-) 30º [fig. 1]
DEBRIS REMOVING AREA: 55% [fig. 1]
ROTATION TO FAILURE: 560º
PEAK TORQUE AT FAILURE: 88.57 gf/cm
60 ̊ DEFLECTION: 2.32 g
PLASTIC DEFORMATION: 0º
FILE CORE AREA RELATIVE TO CIRCUMFERENCE AREA: 28%
FILE CORE AREA RELATIVE TO FILE X-SECTION AREA: 62%

 

DISCUSSION:

  • Manufacturer claims a booster tip comprised of 6 cutting sides but its sides are so small that they actually form a non-cutting tip. The tip will not negotiate a canal having a smaller diameter without burnishing its way into the canal and resulting in greater torsional stress.
  • The finish is excellent and the blades are sharp.
  • Testing shows the recommendation of using 2-3 files is overly ambitious as is the recommended use of long strokes for insertion.

TIP SEM

Fig. 1 : TIP X-SECTION

Fig. 2

 

 

 

 

 

 

 

 

POST A COMMENT

DOWNLOAD PRINTABLE PDF

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

Circumference&AreaKey

 

 

 

 

 

 


 

FLUTES & SPIRALS:
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

 

 

 

 

 

 

 

 

 


 

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

Helix Angle

Helix Angle

 

 

 

 


 

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

DebrisRemovalArea

 

 

 

 


 

DEFLECTION & DEFORMATION:
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.

Deflection

 

 

 

 

 

 

 


 

ROTATION TO FAILURE:
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:
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

Screen Shot 2015-02-04 at 7.24.00 PM

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.

 

DOWNLOAD MASTERING ENDODONTIC INSTRUMENTATION (original award winning text)