frequently asked questions

Are One Endo Files simple rotary or reciprocating instruments? »
The One Endo File may be used as both a reciprocating and rotary file. For use as a reciprocating instrument however, the greatest angle of rotation must be clockwise as the One Endo File will not cut during a counter-clockwise rotation.
At what speed should the One Endo File be used? »
We recommend setting your speed to 550rpm.
What handpiece should I use with the One Endo File? »
The One Endo File is not dependent upon a specific handpiece, nor do we recommend one particular brand over another.
Do you offer reduced pricing for students? »
NanoEndo offers a discounted rate to residents and faculty of endodontic programs. To gain access to our endo program order form, please submit a request HERE.
Are NanoEndo files available in different lengths and/or with shorter handles? »
While our files are currently available in one length (23mm One Endo; 25mm EXO Endo) on our online store, we are happy to make any length of file with either a long or short shank handle with a minimum order of 100 packs/each custom size. For more information about our custom file sizing, please email us at or call 844.ONE.FILE (663.3453)

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How is your company different from others? »
NanoEndo is continuously conducting comparative research for different types and brands of endodontic files. We present results for all to see and let the chips fall where they may. We also encourage your participation in designing comparative testing, as long as you agree that the results can be published. We have two objectives: one is to convey information, and two, is to continuously use accumulated information to enhance our file designs. Our goal is to enable you to distinguish marketing hype from meaningful and factual clinical data.Request a Test
If your instrument designs are evidence-based, will you be changing your designs if there is a change in the evidence? »
NanoEndo will make design modifications as soon as evidence indicates a modification is merited. On the other hand, modification changes will not take place just for the sake of marketing; changes will be dictated by opportunities for improvements.
What if a competitor’s file tests better than your own? Will you publish this data alongside your own? »
One of our objectives is to convey information; that includes any information that might appear to be unfavorable to our products. We will always point out the limitations as well as the attributes of our products so that you may use them to their greatest benefit. But, we will always use any limitations as a challenge for improvement.
Do you have plans to introduce other types of files? »
Incorporating the unique feature of having two tapers, side by side in the same instrument, enhances virtually all types of files. NanoEndo is already planning the introduction of additional file designs having this feature. However, any new introduction would have to constitute an improvement over the other existing file brand.
How do you plan to promote your instruments? »
Although we will use all of the traditional avenues for promotion, our main thrust will be through the Internet. Other than personal contact, we feel that online communication is the most expeditious and comprehensive means for dissemination of information. Actually, we anticipate NANOENDO.COM will become an informational hub for all endodontic files. Dentists are always welcome at our facility for hands-on instruction on our instruments at no charge. NanoEndo offers a very generous opportunity for skilled practitioners to conduct seminars for teaching the best use of our instruments.

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How does your clinical simulator testing differ from testing recommended
ADA specifications? »

To test the validity of claims for file designs, a computerized clinical simulator was constructed to simultaneously measure torque, pressure, and time, during the prescribed use of instruments, to determine efficiency and the threat of file failure. The simulator A computer provides the means for precisely duplicating motions designed to simulate clinical applications for comparing different instruments rather than using a very specific circumstance for testing.

While eliminating operator variability and conforming to operation recommendations, computer programming can control the preparation parameters for the depth and the speed of file insertion and withdrawal, as well as the speed of file rotation. Not only can the stress of the force of insertion and torsion of each individual file size and taper be measured under different circumstances, but also the stresses, using different file sequences, can be recorded in order to determine the least stressful and most expeditious technique approaches.

All measurements are plotted over time to illustrate when and how stress occurs. Rather than measuring the over-all flexibility of the file, the simulator device can be used to measure dynamic flexibility, recording the resistance to bending as a rotating file progresses onto an inclined plane or simulated curved canal. The measurement occurs over time as different diameters and cross section configurations of the file transverse a curvature.

The logged data help determine the methods for which each instrument may be used most effectively while minimizing the threat of failure. The simulations can be applied to different anatomies and technique solutions quickly become apparent, rather than having to rely on subjective and time consuming trial and error experience that lack the benefit of controls. An examination of the results puts the manufacturer’s technique recommendations in perspective, validating or invalidating their claims. Identifying technique enhancements and file design improvements become more feasible. The results can be used to substantially enhance efficiency and may be surprisingly different from what has been recommended.

Irrigation and lubrication can reduce torque requirements by as much as 400% compared to rotating in a dry canal. However, shorter strokes of insertion can be more effective than carrying the rotating file to greater depths into the canal with fewer insertions, even with irrigation. The percentage of the file engaging dentin plays an important role in influencing the torque reduction resulting from lubrication or clearing of debris by irrigation.

When the rotating file becomes engaged for more than a few millimeters, the interface of irrigation is reduced between the surface of the canal and the file. This has little effect in reducing torsion, since any irrigation has little opportunity to penetrate the additional distance with the file due to the rotating file moving the irrigating solution in a coronal direction. This is especially the case when the irrigation is intermittent rather than constant and the insertion of the file is continuous rather than being done in shorter strokes. The use of a handpiece, having a tubular connection with an irrigation pump, can be beneficial even with a short stroke technique, not so much for lubricity, but for the elimination of debris before its accumulation contributes to resistance of rotation.

What does testing tell us about avoiding file cyclic fatigue? »
With the frequency of curvatures, we should assume their presence in a plane that is not apparent on radiographic examination. Only with very careful consideration of variations in the pressure required for progressing into the canal do we determine if curvatures are threatening file failure. One of the greatest problems in making that determination is the force required for rotating a large diameter file relative to the force necessary to progress through a curvature. Gauging the depth that the file can be inserted into the canal, before the file is rotated, can be especially helpful in determining the resistance due to curvature as opposed to the resistance caused by a constricted canal. Knowing the limitations of the file size and taper determined from testing, and their relationship to the canal anatomy, can definitely improve the ability to avoid file failures due to fatigue or torsion.
What determines a file’s cutting ability? »

The cutting ability of a file is primarily the result of its cross-section design when the taper and technique are the same. The angle of incidence of the blade and the width of the land, shown in cross-section perpendicular to the blade, are the best indications for comparing different files for cutting ability. The helix angle certainly should be considered in conjunction with the cross-section design in order to maximize the efficiency of a particular file. It is important to note that comparisons of cutting abilities of some files often change at different diameters along the working surface due to changes in the ratio of the depth of flute and file diameter, the width of lands, and the helix angle. Cutting ability is synonymous with cutting efficiency. However, the term cutting efficiency of a file would more appropriately be reserved for describing the entire working surface that becomes engaged rather than a measurement at one diameter.

What tactile sensations indicate efficient or effective rotary instrumentation? How an instrument feels offers little information about the collective stresses on a file. Contrary to the practitioner’s usual reliance on the tactile sensations of torsion for conventional hand files, stress on rotary files, as the result of the force of cutting, can most accurately be determined by testing. The results can be very different from the indications of tactile sensations. Since variations in torsion (those rotational forces that would urge the handpiece to move in a counterclockwise direction if the file remained in a stationary position) are difficult or impossible to feel, the tactile sensations of a rotary file are primarily due to variations in pressure, which can offer indications for a needed response. For instance, when applied pressure results in the negative pressure of screwing-in, then an immediate response of removing the file from the canal is needed in order to prevent the stress of excessive engagement. Or when a greater pressure is required for continued advancement into the canal then the file should be removed in order to avoid ledging or subjecting the file tip to excessive stress. With no comparative basis for applied pressure, the uninformed user may likely select a file with inefficient scraping edges for having a smoother feel than one with more efficient less stressful cutting edges.

Cutting effectiveness, it should be pointed out, depends on more than just the sharpness of the cutting blades. It is also the result of the angle of incidence, helix angle, taper and flute design and the relationship each of these instrument features has with the file sequence and technique used.

Why do some files seem to screw into the canal?»

Often underestimated in importance is the fact that to rotate a file can be due to the force of caused by the blades becoming engaged by cutting into the canal wall to form chips without dislodging them. When the blades are parallel or the helix angles are the same along the working surface, the file becomes an effective screw. Torsion results when any screwing-in force is resisted and can cause the file to become locked in the canal. Parallel blades and more spirals are a carry-over from the hand file design when instruments were twisted during manufacturing and the ‘watch-winding’ motion was used as a reaming technique. Screwing-in forces can actually be augmented with sharper cutting angles further complicating the formula for efficiency. Several file manufacturers utilize accelerating helix angles to reduce the screwing-in forces. For instance, a 22-degree helix angle at the tip of the file may be graduated to a 45-degree angle at the handle end. As both ends of the working surface are engaged, the different angles have different screwing-in rates, feed rates, and much of the torsion of screwing-in is reduced. However, most of the working surface of the file with graduating helix angles needs to be engaged before the different blade angulations have much benefit in canceling out some of the screwing-in forces and when most of the file is engaged that in itself increases torsion. If only a small portion of the file becomes engaged, the screwing-in forces may require most of the force for rotation. The operator may notice this pulling-in force if only a short portion of the file becomes engaged in a constriction.

The speed of rotation can have a significant influence on the screwing-in forces and the resulting torsion. The optimum rotation speed for efficiency remains approximately the same independent of the canal anatomy. Slowing the speed of rotation as a precautionary measure can result in additional torsion because the screwing-in forces may increase by allowing the blade to become too deeply engaged to dislodge the chips that are formed. The most efficient design incorporates only the minimum number of spirals that are necessary to effectively remove debris. In doing so,more positive cutting angles can be utilized and the decrease in the number of spirals of the blade reduces the amount of its engagement. The result is a reduced required torque for rotation and increased efficiency.

What are the different types of file tips and what differences do they make? »
File breakage can occur by applying excessive torque while attempting to enlarge a canal that has a smaller diameter than the non-cutting portion of the file tip. Instrument tips have been described as cutting, non-cutting and partially cutting although there is no clear distinction between the types. The tip has two functions. One function is to enlarge the canal. The other function is to guide the file through the canal. Without understanding the tip design of a particular instrument, one is apt to either transport the canal if the tip is capable of enlarging the canal and it remains too long in one position, or encounter excessive torsion and break the file if a non-cutting tip is forced into a canal having a smaller diameter than its tip. Transportation of the original axis of the canal can occur by remaining too long in a curved canal with a tip that has efficient cutting ability. On the other hand, there is no need to remain too long in one position and the efficient cutting can facilitate enlarging or negotiating constricted or blocked canals. The angle and radius of its leading edge and proximity of the flute to its actual tip end determine the cutting ability of a file tip.
How do I determine the optimum rotation speed?»
The optimum speed of rotation is determined by two factors: the helix angle and the amount of engagement. The feed rate of the file, or how fast the file would screw-in if no resistance were met or no force were applied, is determined by the helix angle. If the file progresses into the canal at the same rate as its feed rate, maximum engagement occurs with minimum chip dislodgment that results in maximum torque. For this reason, slowing the rotation for the sake of reducing the threat of failure in complex anatomies can actually increase the amount of engagement and the likelihood of failure if the rotation speed approaches the feed rate determined by its helix angle. If the file progresses into the canal faster or slower than the feed rate, the depth that the blades become engaged is reduced and greater chip removal occurs. The optimum speed is the speed that causes the least amount of stress, and changing to a slower or increased speed can increase the stress on the file even in compound curvatures. Optimum rotation speed is also determined by the amount of the circumference of the file that is engaged. If only the side of the instrument is in contact with the canal, the force of torsion is virtually eliminated and the speed of rotation can be substantially increased to augment its effectiveness the file is prevented from becoming circumferentially engaged and the tip remains passive. Using this technique can be very expeditious in preparing an anastomosis, fin, or intentionally relocating the orifice of the canal. The trend seems to be to slightly increase the speed of rotation and decrease the speed of advancement into the canal.
How does file engagement affect breakage? »
Torsion is directly related to the amount of file engagement. The torque required to rotate a large area of the working length of a file may cause excessive stress on the smaller diameter portion of the file, resulting in failure. Since the area of the working surface is comprised of the length and the diameter, the torque required to rotate a tapered instrument with 16 mm of engagement may be significantly more than two times as great as is required for one with 8 mm of apical engagement. Reducing the length of the working surface can certainly reduce the potential of engagement and, therefore, its propensity for failure. The minimum torque required for the maximum diameter portion of the file to function in the canal can be more than sufficient to break the smaller tip diameter portion of the file if it becomes bound in the canal.
Why are different tapers used? »

Employing different tapers can be one of the most important methods of limiting file engagement.The nomenclature, however, for describing the techniques for using tapered files can be confusing to the novice in conceptualizing the action that is occurring if one is only considering an individual file rather than a sequence of files. If a smaller tapered file is inserted into the preparation of a larger tapered canal, only the apical portion of the file initially becomes engaged, yet the technique is termed. On the other hand, crown-down is more meaningful when referring to that portion of the canal being first enlarged during a sequence from large tapers progressing to smaller tapers. Conversely, if a larger tapered file is inserted into a smaller tapered canal, the file initially engages and prepares only the coronal aspect of the canal and yet the sequence technique is called a approach. The distinction is important in order to keep in mind which part of the file is being engaged and is being stressed. In either technique, one advantage in changing from one taper to another is that the initial engagement is minimal and any increase in engagement is gradual, thus enabling an opportunity to more accurately interpret variations in resistance as the file progresses into the canal. That opportunity might not be available when using files having the same taper since this approach can quickly result in full engagement with minimum apical advancement.

The operator is better served if progress into the canal is terminated before maximum engagement occurs. One of the most important considerations for rotary instrumentation is utilizing the advantage of changing file tapers. The reduction of stress on the instruments can significantly be achieved by minimizing engagement with this technique.When using the crown-down technique, only the file tip, the portion least resistant to torsion failure, initially becomes engaged. When using the step-back technique, a larger diameter, the more torsion resistant portion of the file initially becomes engaged. In contrast, if the canal preparation of one file is followed with a file having the same taper, file engagement is maximized, increasing the torque requirement that increases the stress on the file.

Does changing the sequence of file tapers used change the amount of engagement? »
The amount of engagement can be precisely determined mathematically and limiting engagement can be accomplished by the selective sequencing of instrument sizes during instrumentation. An important factor to remember is the mathematical relationship between the distance the file progresses into the canal and the amount of engagement that occurs. Many dentists erroneously assume that the amount of engagement equals the depth of insertion. When using files having the same taper, an abrupt change can occur in the amount of engagement with a minimum amount of additional advancement into the canal. For example, if a canal has been prepared to a size 40/.04 taper, a size 35/.04 taper file can prepare the canal to a 1 mm greater depth and only the apical 1 mm of its tip will become engaged. Any greater depth of advancement can cause the entire working length of the file to become simultaneously engaged and the torque required for rotation may be more than necessary to break a the tip if partly bound. Tactilely determining when minimum engagement changes to maximum engagement can require more time than is necessary in order to avoid file separation and is best determined mathematically.
What are the most important considerations in following a technique? »

The primary consideration is to set parameters for preventing file failure and eliminating unnecessary or counterproductive actions. By observing the situations that usually have a high incidence of file separation, we can then test procedures to effectively avoid those situations. Once effective procedures are identified, then the most efficient approach can be determined. The incidence of file failure during testing indicates instrumentation should encompass considerations for all of the following parameters for rotary instrumentation:

  1. Advance into the canal using no more pressure than was required to advance the first 1mm.
  2. 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).
  3. Advance a file into the canal with no more than 1mm increments with insertion/withdrawal motions.
  4. Advancement into the canal should be able to occur at a rate of approximately 0.5mm/s without increasing the pressure of insertion.
  5. Follow the use of one file with a file having a different taper.

When any of the parameters cannot be met, changing to a file having a different taper in the technique sequence will usually enable re-adherence to the parameters. These parameters, by necessity, require subjective and arbitrary judgments, since there is no one point at which file breakage definitely occurs or definitely does not occur. However, careful examination during extensive testing indicates that any exception to these parameters should be undertaken with the cautious awareness of the operator.