Precision Based Endodontics
Recently a new endodontic file has been introduced to the dental profession. This is the EndoSequence file by Real World Endo and Brasseler USA. Representing a new philosophy, based on precision and simplicity, the EndoSequence file is part of an overall technique that will truly make your endodontics better and more predictable. But first, what do we mean by precision based endodontics?
Precision based endodontics is a Real World Endo term that signifies the goal and results you’ve always wanted in your endodontic therapy. Precision and predictability! Precision in your instrumentation technique achieved through the concept of “machining” a fully tapered preparation. We are no longer merely filing root canals. Through the benefits of advanced file design we now have, for the first time, the ability to truly machine (or mill) preparations. Along with the concept of milling anything, comes the concept of precision. The EndoSequence technique has also been designed to generate precision in your obturation results, through a matching system of laser verified gutta percha cones. Lastly, the net result of all these techniques is predictability. Predictability achieved through the synchronicity created between a machined preparation and a matching laser verified master cone. This ability to achieve synchronicity in a simple, straight forward manner is the change in philosophy.
Real World Endo agrees with others who, in effect, have said that one of the biggest obstacles to endodontic success has been and remains the step-back preparation. We strongly believe in using a constant taper file sequence such as a .04 or .06 taper to shape the root canal preparation. A variable taper protocol, in our opinion, does not work nearly as well clinically, as it does on paper. Think about it. A variable taper sequence is nothing more than a step-back preparation from the opposite end of the tooth! As a result of better quality manufacturing, we now have the ability, with a series of constant taper files, to create predictable, reproducible shapes. A variable taper sequence always results in a different shape each time you do a root canal. The result? A lack of reproducibility and synchronicity that will make obturation more challenging.
Additional benefits of a constant taper sequence come after we have created a fully tapered .06 preparation. This is the primary cone fit and ease of obturation. Instead of guesstimating and becoming frustrated with bent cones, a constant taper preparation (.06 taper in particular), makes the primary cone fit a “no brainer.” Naturally, this becomes even easier when the master cone is laser verified and matches the preparation.
To achieve the necessary synchronicity between preparation and the master cone, we need to start with the file. Everything starts with the file. There are numerous design features that readily distinguish the EndoSequence file from previous generations of rotary files. In fact, we believe the EndoSequence file should be considered the first 4th generation rotary file. But to fully understand this statement, we need some historical perspective on rotary files.
The first nickel titanium rotary file (1st generation) introduced into North America was the Lightspeed System. This file, although similar to the stainless steel Canal Master, changed the way we thought about performing endodontic procedures. The Lightspeed gave us the option of using nickel titanium rotary instrumentation in addition to (or in place of) stainless steel hand files. This was a seminal event in the history of endodontic preparations. The Lightspeed took us out of the dark ages of hand files into the bright light of rotary instrumentation.
The next generation of rotary files (2nd generation) were those files that had radial lands. Examples of these files are the Profile, GT, Quantec, and K3. All of these files have radial lands, although some have full lands (Profile, GT) while others (Quantec, K3) have recessed lands. While design differences do exist between these files, in areas such as pitch and helical angles, the overwhelming similarity is the existence of radial lands.
Although the radial lands are helpful at centering, they reduced flexibility and significantly increased the torque requirements of the respective files. All radial lands create an increase in working torque requirements. This is a result of their decreased cutting efficiency, along with an increase in lateral resistance (drag). In fact, the problem with radial lands has been so significant, some file systems (GT, Quantec) have even employed a variable taper protocol in an attempt to minimize engagement and therefore, increase cutting efficiency. Unfortunately these attempts have met with limited success. Files encumbered with radial lands do not have excellent cutting (shaping) ability. Furthermore, a variable taper sequence creates variable shapes. As a result of employing a variable taper sequence, a lack of synchronicity will exist between the preparation and the master cone.
A case may be made that the third generation of rotary files consists of the ProTaper and the RaCe. Both of these files are considered third generation due to their lack of radial lands and their individual attempts at addressing increased cutting efficiency. To their credit, these files were a product of “thinking out of the box.”
The ProTaper, with its modified K file design, addressed the need for increased cutting efficiency through the use of a progressive taper. The ProTaper has, in fact, achieved improved cutting efficiency. However, excessive working torque, at the tip of this file as the result of its progressive taper and the lack of a centering device are limitations.
The RaCe file on the other hand addressed the need to reduce overall working torque by incorporating an alternating spiral design. The alternating spiral design, however, has made it difficult to determine if the file has been unwound, as a result of excessive torque. Furthermore, the RaCe file, although effective at reducing torque, also does not have a definitive centering device. Lastly, the RaCe file is used in a variable taper protocol, thereby resulting (again) in variable shapes.
The introduction of a 4th generation rotary file begins with EndoSequence. When we examine the EndoSequence file, it is readily apparent that this file is a product of both evolution and revolution. Let’s examine the following: design features and performance.
- Blank Design
The blank design of the EndoSequence file is absolutely revolutionary. The basic design is that of a reamer, not a file. This is a significant change by itself in rotary file design. However, there is much more!
The EndoSequence file is designed in such a way that there are alternate contact points (ACP’s) along the shank of the instrument. This innovative design not only keeps the file centered in the canal, but the alternate contact points greatly reduce the torque requirements of the file. This is because alternate contact points reduce engagement and greatly reduce the lateral resistance of the file. The EndoSequence file is never fully engaged along its entire length.
Additionally, the Sequence file has been shown to have the “least resistance to deflection of any constant taper rotary file.” This is very significant because when this property is combined with the alternate contact points, the result is a file that will stay centered.
There are even more significant features to the ACP design. Because the alternate contact points, in combination with a non cutting (precision) tip, keep the file centered in the canal, there is no need for radial lands. This is profound because the lack of radial lands allows the instrument to be sharper and consequently more efficient. Additionally, the lack of radial lands, results in a decreased thickness of metal. The result of less metal is a dramatic increase in flexibility.
- Metal Treatment
Another distinctive feature of the EndoSequence file is that it has been subjected to the process of electro polishing. This is very significant because of the benefits gained from such a treatment. But, what are some of the benefits gained from such an enhancement?
Electro polishing removes many of the imperfections in the nickel titanium that can have catastrophic consequences. For example, electro polishing is very effective at inhibiting crack propagation in NiTi blanks. These cracks have been shown repeatedly to be a major cause of instrument separation. Additionally, the creation of a superior finish will keep the edge of the NiTi instrument sharper, cleaner, and more durable. The result of these benefits is a rotary file with more cutting efficiency, less lateral resistance, and increased resistance to wear. Simply put, electro polishing makes any rotary file, a safer and a better rotary file.
We can categorically state that, at the current time, the EndoSequence file is the only constant taper rotary file that is subjected to an enhancement procedure such as electro polishing. We do it for a simple reason. Your patients deserve it!
- Tip Design
It has always been a goal of Real World Endo to have clinicians perform not only efficient endodontics, but safe endodontic procedures as well. Consequently, the EndoSequence file utilizes a precision tip. A precision tip is, by definition, a non cutting tip that becomes fully engaged right at D-1. The result is safety (non perforating) combined with efficiency. This is exactly what we want to have in tip design. It truly is amazing how such an effective cutting file can remain centered in the canal. This ability to remain centered without radial lands, is the result of a precision tip combined with alternating contact points. This is a new and revolutionary concept.
- Pitch / Helical Angles
The EndoSequence file has both variable pitch and variable helical angles. This results is less of a tendency to pull you down into the canal. This is further enhanced by its blank design (ACP’s) and the lack of radial lands. The net result of these features is greater control. Control over the the file, control over the procedure.
- Quality of Manufacturing
Nickel titanium rotary files are ground, not twisted like hand files. In fact, the EndoSequence files are made (ground) in Switzerland. It is not sufficient to say that just because something is “Swiss-made” it means it is excellent. However, there is a certain connotation to “Swiss-made” and quite honestly the “Proof is in the Pudding.” Real World Endo is committed to the concept of precision based endodontics and this precision is a function of the quality of manufacturing.
Pick up an EndoSequence file and inspect it thoroughly. Rotate the file slowly in your fingers and check the consistency of rotation. Do you see a shadow consistently climbing up the helical angles from the tip to the handle? We imagine you do. Now, inspect the edges and confirm their sharpness. When you push the file across your fingernail (cuticle to tip), you will feel it bite and engage. The sharp edges are a function of its manufacturing process.
Next, we want you to confirm the flexibility of the EndoSequence file and, more importantly, test the shape memory of its nickel titanium blank. The shape memory is superb. It does not hold a curve like some other rotary files. Additionally, we want you to try and separate the handle from the shank. You will quickly realize that it is next to impossible to do so. All a result of excellent Swiss manufacturing.
It becomes readily apparent that to consistently achieve precision based endodontics, we need manufacturing excellence combined with clinical control. Therefore, it is with supreme confidence that we can say the EndoSequence file has been manufactured to the highest possible standards. We challenge any other manufacturer to meet these simple, yet rigorous standards.
- Cutting Efficiency
The Sequence file has superb cutting efficiency. What gives this file such efficiency is the electro polishing that results in its characteristically sharp edges. Furthermore, the ACP design allows the portion of the shank that is engaged to really work in an efficient manner. This is because the full shank is never totally engaged, nor is there the encumbrance of radial lands.
Experience has shown us that the EndoSequence file cuts so effectively that the clinician must be aware to wipe clean, or, change the file after three pecks (or engagements) of the file. After a very brief period of time ( 3 to 5 seconds), you can actually see the flutes (which are a reamer design) begin to accumulate debris. Consequently, the clinician and their assistant need to be conscientious about cleaning the file. You should only be in the canal with this file 3 to 5 seconds before cleaning or moving to the next sequential instrument.
Another tribute to the EndoSequence file’s cutting efficiency, is how fast it can enlarge a canal preparation. For example, many times you may be able to reach the working length of a mesial buccal canal (in a lower molar) with only a size 15 file. The following attempt to enlarge this preparation to a 20, 25, or 30, may be extremely difficult and frustrating. It is absolutely astonishing how the Sequence file will take such a situation and very quickly be able to enlarge the preparation to a 25 or 30! Best of all, there is no transportation. The ability of this file to withstand transportation is a function of its alternating contact points, precision tip, and excellent flexibility. Try doing this with any other fully tapered, landed file and you will immediately notice the difference.
The EndoSequence file without question generates the least lateral resistance of any constant tapered rotary file system. This is just the facts. The decreased resistance is a result of the lack of radial lands, a triangular reamer-like design, extremely sharp edges, and electro polishing. The manufacturer has combined all these features into a single file, with the result being the lowest torque requirements of any constant tapered rotary file system.
As previously mentioned, the flexibility of this file is outstanding. The ability to create a file that stays centered, without the need for radial lands, results in greater flexibility of the file. Flexibility becomes a tremendous asset in rotary endodontics, as the clinician begins to tackle more difficult cases. Without question, we will continue to be challenged by more difficult endodontic cases. Consequently, the need to have a flexible file becomes paramount as you desire to perform more sophisticated endodontics.
However, a key point to remember concerning flexibility is this: Flexibility is not the same among the various rotary files, and it most certainly should not be taken for granted.
The EndoSequence file has been shown repeatedly through test cases (both clinically and bench top) to work best in a range of 500 - 600 RPM. The ideal speed may vary a little according to your personal preference and engine. Every engine we have worked with seems to have an optimal RPM for specific files. This is analogous to marine engines where a boat will plane and perform smoothly at a certain RPM, but at other RPM’s the boat will experience some noise and vibration.
We understand that some clinicians may be hesitant at first to run these files at 600 RPM. In this case, a little formula may be helpful. E= T & S. This means that the energy required to remove dentin (E) is a function of both torque (T) and speed (S). Consequently, as one reduces the torque requirements you can run the file at a higher RPM. But why do this? Because in industry as craftsmen wish to perform more precise work, they run their machinery at higher rates of speed and employ finer cutting instruments. We have had a similar experience in dentistry. The move from belt driven low speeds to high speed turbines. Why? For more precise work!
As previously mentioned, our personal preference for the EndoSequence file is 600 RPM in portqble engines and 500 RPM in bench top models.
We have just introduced to you the design features of the new EndoSequence file. Performance related aspects have also been discussed. However, there is another innovation associated with the EndoSequence technique. That is the Expeditor.
The Expeditor is a 21 mm, size 27, .04 taper nickel titanium rotary file. The EndoSequence technique is based upon the concept of using an Expeditor file, choosing the correct canal size (small, medium, or large) and using the corresponding package of files to properly prepare the canal. Generally, canal preparation will require only three files, but there is a fourth file in each assorted pack for the more challenging cases.