Products and techniques that will make your endodontic experiences better!
By Kenneth Koch, DMD, and Dennis Brave, DDS
Real World Endo Sequence File System
The "Sequence System" has been designed to work well for both the specialist and the general practitioner. Real World Endo has developed a system and technique that is both safe and efficient. Neither aspect has been compromised at the expense of the other. When compared to previous rotary files, the Sequence File can be classified as the only fourth-generation rotary file. To fully understand the system, we need to begin with a discussion of the file characteristics.
The blank design
The blank design of the Sequence File is revolutionary. Previously, it had been thought that radial lands were required to maintain a rotary file centered in a canal. With the introduction of the Sequence File, we have been able to bring you a file that will stay centered without radial lands. This goal has been achieved through the use of alternate contact points (ACPs) along the shank of the instrument (Fig. 1).
This innovative design not only keeps the file centered in the canal, but the alternate contact points significantly reduce the torque requirements of the file. This is because alternate contact points greatly reduce the resistance of the file.
There are other significant features to the ACP design. The lack of radial lands is profound because it allows the instrument to be sharper and thus more efficient. Additionally, it allows for decreased metal thickness resulting in a dramatic increase in flexibility. Clinicians will be amazed at how flexible a fully tapered .06 rotary file can be when not burdened by the extra metal required for radial lands.
Sequence Files are electro-polished. This is significant because electro-polishing removes many imperfections that can lead to unexplained separation and other troublesome consequences. For example, electro-polishing is effective at inhibiting crack propagation in NiTi blanks. These cracks have been shown repeatedly to be a major cause of instrument separation. Additionally, a superior finish will keep the NiTi instrument sharper, cleaner, and more durable. The benefit is more cutting efficiency, less lateral resistance, and increased resistance to wear. Electro-polishing can, in fact, extend the life of a rotary file. However, the Sequence File has been designed ideally to be part of a single-use system. Simply put, electro-polishing makes any rotary file a safer and a better rotary file (Fig. 2).
The Sequence File is the only constant-taper rotary file system enhanced with electro-polishing. This is a significant advance in the manufacturing of constant-taper files.
Quality of manufacturing
It is not sufficient to say that because something is "Swiss-made" means that it is excellent. Nevertheless, there is a certain connotation to the term, 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. The Sequence File is Swiss-made and the quality is obvious.
Pick up a Sequence File and inspect it thoroughly. Rotate it 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 pull the file across your fingernail (cuticle to tip), you will feel it bite and engage.
Next, confirm the flexibility of the Sequence File and, more important, test the shape-memory of its nickel titanium blank. Some manufacturers use NiTi blanks that exhibit extreme flexibility and excellent shape-memory. Other manufacturers use blanks that are stiff and actually seem to hold a curve. The quality of the NiTi blank is a little-known factor of file design, but has serious consequences. Test for yourself the shape-memory of the Sequence File. We think you will find it superb.
Additional aspects of manufacturing quality can be seen by the following test. Simply turn the file around and look straight down on the file as it is rotating in the handpiece. Check to see if the file is running true (tight, concentric revolutions), or is there a wobble? A wobble signifies a less-than-ideal manufacturing process.
It is with supreme confidence that we say the Sequence File has been manufactured to the highest possible standards. We challenge other manufacturers to meet these simple yet rigorous standards.
The Real World Endo Sequence File is available in both .04 and .06 tapers. Most important, these are fully tapered files. This means the working shank is a full 16 mm, not 9 or 10 mm. This is significant because a full working shank will allow the practitioner to efficiently "machine" a preparation in a precise, crown down fashion. Not only will this technique contribute to painless endodontics, it will make the primary cone-fit an easy match. Obturation becomes much easier when you have a fully tapered, machined preparation.
A primary goal of Real World Endo is to have clinicians perform endodontics not only efficiently, but safely as well. Consequently, the Sequence File uses a precision tip. A precision tip is, by definition, a noncutting tip that becomes active right at D-1. The result is safety (nonperforating) combined with efficiency. This is exactly what we want to have in a tip design (Fig. 3).
It is amazing how such an effective cutting instrument as the Sequence File can remain centered in the canal. This ability is the result of a precision tip combined with the alternating contact points (ACPs) of the blank design. This is a new and revolutionary concept.
Cutting efficiency of rotary files has received much attention in the past few years. The more efficient a rotary file, the less torque is required. The major problem has been radial lands that not only significantly increased torque requirements, they made the files dull and inefficient.
By contrast, the fourth-generation Sequence File has superb cutting efficiency. The only other file that has similar efficiency is the ProTaper. Although the ProTaper also employs a triangular blank design, it is somewhat modified. The Sequence File owes its extra cutting efficiency to electro-polishing. The ACPs allow the engaged portion of the shank to work efficiently because the full shank is not totally engaged nor is there the encumbrance of radial lands.
The Sequence File cuts so effectively that the clinician must clean or change the file after three pecks (or engagements) of the file. After a brief period of time (3 to 5 seconds), you can actually see the flutes (which are of a reamer design) begin to accumulate debris. This is the result of superb cutting efficiency. Con-sequently, the clinician and 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.
Its high efficiency also enables enlargement of the canal with speed and precision. For example, 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 subsequent attempt to enlarge the preparation to a 20, 25, or 30 may be extremely difficult and frustrating. The Sequence File will take such a situation and very quickly enlarge the preparation to a 25 or 30! Best of all, there is no transportation. Its ability to withstand transportation is a function of its ACPs, precision tip, and excellent flexibility. Try doing this with any other fully tapered, radial-landed file and you will immediately notice the difference.
We have found that, without question, the Sequence File generates the least lateral resistance of any constant-tapered, rotary file system. This 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, resulting in the lowest torque requirement of any constant-tapered, rotary file system.
Flexibility is a design feature that received much attention when rotary files entered the marketplace. Through the years, the flexibility of NiTi files has become sort of a "given." Well, guess what? It is not a given. There is tremendous variation in flexibility among rotary files. While it is true that design features can affect how well a file performs, flexibility still remains a critical quality for rotary files.
Many factors can affect flexibility such as the manufacturing process, blank design, and the presence and width of radial lands. Superior flexibility becomes a tremendous asset in rotary endodontics as the clinician begins to tackle more difficult cases. We will continue to be challenged by more difficult endodontic cases. Therefore, the need for a flexible file becomes paramount.
The key point to remember concerning flexibility is this — flexibility is not the same among the various rotary files available, and it certainly should not be taken for granted.
Pitch and helical angles
"Pitch" is the number of spirals or flutes per unit length. Pitch is important because a constant pitch will work much like a wood screw and pull itself into the tooth. This was a significant problem with some of the early-generation rotary files. In contrast, a variable pitch design will significantly decrease the tendency of the file to get drawn into the tooth. This is particularly important when using tapers of .06 or greater.
The Sequence File has both variable pitch and variable helical angles. The result is less tendency to pull itself into the canal. This is further enhanced by its blank design (ACPs) and lack of radial lands. The net result is greater control. Control over the file equals control over the procedure.
To consistently achieve Pre-cision Based Endodontics, we need manufacturing excellence combined with clinical control. Although the Sequence File is very efficient at cutting, it nevertheless has excellent debris removal as a result of its variable helical angles.
The Sequence File has been shown through test cases (both clinically and bench-top) to work best in a range of 500 rpm to 600 rpm. The ideal speed may vary slightly according to your personal preference and engine. Every engine 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 will experience noise and vibration at other speeds. Our personal preference is 600 rpm. We have found this works well in multiple engines. We particularly like the way the Sequence File performs in a portable engine (Fig. 4).
Historically, portable engines have had a challenge when running fully tapered .06 rotary files. This was because the radial lands on previous generations produced excessive lateral resistance. Now, thanks to the ACP design (no lands), and extremely low torque requirements, the Sequence File runs superbly in a portable handpiece.
We also must point out that the Sequence File has a tendency to "click" in the canal. In the past, this could be cause for alarm. Clicking is not unusual for a triangular-shaped blank; but, if the clicking becomes a clacking (or very noisy), it means you are pushing too hard on the file. Reduce your force and the clacking will disappear. Do not reduce the rpm. Clacking is a result of excessive force, not rpm.
It is our experience that rotary files run at too low a speed (150 rpm to 175 rpm) will actually result in increased breakage. This is because the file is going so slowly that there is a tendency for the clinician to force the file. Never force a file! Run the handpiece at the proper rpm (500 rpm to 600 rpm) and let the file do the work.
Now that we have discussed the design features of the Sequence File, let's take a look at the clinical technique.
Real World Endo / Sequence File technique
The Real World Endo / Sequence File comes in packages of four files each. The selection of Sequence Files is as follows: The "Expeditor File" (also four to a pack), and .06 taper rotary files in sizes XS/S, M, and L. Additionally, there are .04 taper Sequence Files available in sizes XS/S and M.
We begin all root canal preparations by confirming coronal patency. This is achieved with a No. 10 stainless steel hand file that is taken down halfway into the canal. Coronal patency is important because if the coronal half of the canal is open (patent), it will routinely be open all the way to the apex. Upon reaching the halfway point in the canal, the No. 10 file is "worked" in a back-and-forth motion to ensure an anatomic channel. In fact, if the canal is extremely tight, you may also wish to use a No. 15 hand file.
After coronal patency has been confirmed, we choose an Expeditor File to be the first rotary file placed into the canal. The use of an Expeditor is a new concept using a completely different file (Fig. 5). The Expeditor File is, in fact, a No. 27 /.04 taper rotary file that incorporates a working shank of 16 mm and an overall length of 21 mm. The purpose of the Expeditor is to determine the approximate size of the canal and which package of files should be opened. Addition-ally, the Expeditor creates coronal channeling that reduces the resistance to subsequent files. We have given the Expeditor an overall length of only 21 millimeters so that the clinician does not get tempted to "bury" the file deep into the canal. Remember — efficiency combined with safety.
Upon entering the canal with the Expeditor, we take this file down into the canal until significant resistance is encountered. Significant resistance is when the file no longer progresses in an easy manner. Having met resistance with the Expeditor, we now remove this file from the canal and subsequently choose which package of files to open. This decision is based upon information gleaned from the pre-op X-ray, the resistance of the No. 10 hand file, and the depth of penetration of the Expeditor.
If the Expeditor goes approximately halfway down into the canal, this signifies a small canal. But, if the Expeditor goes down significantly more than halfway, this means the canal is medium-sized. A totally "loose" Expeditor that goes to its entire length signifies a large canal. Once the canal size is determined, simply pick the appropriate pack of files.
For example, in a narrow canal, you may choose to open the package of XS/S files. These are the files for extra small and small canals. Choose the appropriate Sequence File and perform a crown down technique in the recommended manner. For example, in a small canal, begin with a No. 30/.06 file and take it to resistance. Following the initial file, take a No. 25/.06 Sequence File to resistance. Determine the final working length after the second rotary file. Following length determination, take a No. 20/.06 file to resistance. Often, the No. 20 /.06 Sequence File will take you to the working length. But the question remains, "How do I know when I'm finished?" The crown down preparation is complete after you have used the first rotary file that reached the working length with resistance.
There will be times, however, when the No. 20/.06 Sequence File falls short of reaching the working length with resistance. In this case, continue your crown down to a No. 15/.06. Generally, this file will get you to the final working length. If the canal is narrow and you must crown down all the way to the No. 15/.06 file, we do not want you to finish your preparation with this size instrument. Simply go back into the canal with a No. 20/.06 Sequence File and this will readily get you to the working length. This is very easy to do with this technique because the Sequence File is extremely efficient at enlarging a previously created anatomic channel.
The aforementioned technique works very well for the vast majority of cases. Nevertheless, in ex-tremely difficult, narrow canals, we modify the technique slightly to reduce stress on the file.
Real World Endo sequence for extra small canals
As always, begin by confirming coronal patency with a No. 10 stainless steel hand file. This is very important when treating narrow canals. Also, take a No. 12 Sequence hand file into the canal and create an anatomic channel. This procedure will facilitate the rotary instrumentation in such canals. Following the use of the hand file(s), introduce the Expeditor into the canal. Work the Expeditor down into the canal until significant resistance is met. Following the Expeditor, open the package of files labeled XS/S.
You are now ready to begin the crown down procedure, but with one modification. A modified crown down sequence will be substituted for a straight crown down. It is as follows:
Begin the modified crown down preparation with a No. 25/ .06 Sequence File. Take this file to resistance. Generally, this goes down the canal about 15 mm. Follow this with the No. 30/.06 Sequence File. This file will generally go 1 or 2 mm less. After two files, you have successfully pre-flared the coronal half of the canal while maintaining a .06 taper. You may now determine your final working length with a No. 10 stainless steel file and an apex locator. If you wish, you can now confirm an anatomic channel to the apex with a No. 10 or 15 hand file. Following the length determination, return to your original No. 25/.06 file. As usual, work this file to resistance. But instead of just going to 15 mm, it now tracks down to about 18 mm. This is what is really sweet about this technique.
Following this, take the No. 20/.06 to resistance. Quite often, the No. 20 will reach the final working length. If not, continue the crown down with a 15/.06 and generally this will get you to your final working length. As previously mentioned, if you must crown down all the way to the No. 15, we recommend you loop back with a No. 20/.06 Sequence File and take this to length. We do not advocate finishing the preparation with a size less than a 20. This applies to both .04 and .06 fully tapered preparations.
While the modified crown down works very well in difficult cases, there is one additional change that can make your life easier. This is it — Perform this technique with the Sequence .04 taper rotary files, not the .06 taper instruments. You often will find that this is exactly what you need to instrument these challenging cases. Remember, it is all a function of taper.
The Real World Endo Sequence File technique is based on the concept of using an Expeditor file and then choosing the size of the canal. Whether the canal size is small, medium, or large, each corresponding package contains the four files necessary to properly shape the canal. Generally, the canal preparation will require only three files, but we have included a fourth file for those challenging cases.
As with all rotary files, we recommend this system to be a single-use (disposable) technique. Because of the challenge of monitoring cyclic fatigue, Real World Endo recommends strongly that the time has come for single-use (disposable) rotary files in endodontics. There is no reasonable argument against this concept.
While the Sequence File is unique in being both procedural- and precision-based, it is also different in terms of its handling ability. This is a rotary file — like all rotary files — that should not be forced. As previously mentioned, if you "muscle" this file, you will hear a clacking of the instrument. This is a warning to reduce pressure on the file. When you learn the proper technique associated with this file, you will realize that it is merely a matter of guiding the instrument. This is a result of its superb cutting ability.
Additionally, the unique alternate contact points gives this file an unbelievable "feel." You can actually feel the canal with the Sequence File. This is a welcome change from some of the previous rotary files that were noticeably stiff and lacking in sensitivity. As is customary with all rotary files, the clinician needs to establish a firm finger rest when using the Sequence File. The entire procedure can be made very comfortable when combined with a portable handpiece.
The Sequence File is not used like previous rotary files that had radial lands. In other words, we do not take the file to resistance and back, to resistance and back, etc. Nor is the Sequence File used with short, staccato-like pecks. Instead, it is used in a single 1-2-3 motion. We take the file to engagement (1) and back, to engagement (2) and back, and finally to a third engagement (3), and out of the canal. The clinician will quickly learn this rhythm. It is the rhythm of precision endodontics.
Always clean the file after three engagements. Perform two series of three engagements each before going to the next file. Each series of engagements should take approximately no more than 3 to 5 seconds.
But what do we mean by engagement? When you are performing this technique, you can actually feel the Sequence File engage the walls of the canal and begin to work. As soon as you feel the file engage, you should retract the file slightly (1 - 2 mm) and then proceed to go back in for another engagement. By using this technique, you are actually instrumenting the canal millimeter by millimeter.
The improved portable handpiece that is part of the Sequence System allows clinicians to work strictly with their fingers (thumb to middle finger). So instead of controlling the file from the wrist area, (as we do with thicker, landed files), we now have a rotary file that is controlled by finger-tip pressure. This adds significantly to the overall control of the procedure and will more easily allow the clinician to achieve "Precision Based Endodontics."
In Review: Real World Endo / Sequence File technique
1. Confirm coronal patency by hand with a No. 10 Sequence File
2. Use Expeditor to estimate canal size and create coronal channeling
3. Begin crown down procedure
4. Establish working length after second file from Sequence package
5. Complete crown down procedure
6. Obturate the canal using "Sequence" gutta percha
Dr. Dennis Brave is a diplomate of the American Board of Endodontics and a member of the College of Diplomates. In endodontic practice for 27 years, he was the senior managing partner of a group specialty practice. Dr. Brave, formerly an associate clinical professor at the University of Pennsylvania, currently holds a staff position at The Johns Hopkins Hospital.
Dr. Kenneth Koch is the founder and past director of the program in postdoctoral endodontics at the Harvard School of Dental Medicine. In addition to having maintained a private practice limited to endodontics, he has written numerous articles on endodontics and maintains a faculty position at Harvard.
They can be reached at Real World Endo at (866) 793-3636 or through www.realworldendo.com.