The tools at hand

THE SET-UP

“As dentists and endodontists, we all know the importance of proper instrumentation for endodontic success. The following article by Dr. Jeffrey Linden takes a complex subject and explains its many facets in easily understandable terms. With the many file designs and techniques on the market, deciding on one can become overwhelming as well as confusing. Dr. Linden’s article gives a wonderful overview of what is out there, and a systematic method of how to choose the best system(s) for you.”-Dr. Garry Bey, Team Lead

It is important to define our armamentarium with full understanding of its design and function.

Since nickel titanium (NiTi) endodontic files were first introduced, there have been myriad file designs and components to hit the market. While hand instrumentation continues to provide the best tactile information regarding canal anatomy and presence of pulpal tissue remaining in the root system, rotary instrumentation is an important endodontic tool as well.

The basics of what separates several different types of files currently available will be addressed in this article.

Files of today
The evolution of NiTi files with a non cutting tip and varying flare design has made it possible to instrument root canals safely and mechanically while maintaining the original canal shape. This is truly a revolutionary advancement.

Files of varying tapers incorporated in the same blade with multiple helical angles and different pitch are significant design and function changes. With these developments, the “step back” technique is now an anachronism to the universally accepted “crown down” approach to instrumentation.

This can be accomplished only with NiTi rotaries. Clinical research has shown productivity increases of 500% achieved concurrently with improved quality and shape. Still, there is some confusion associated with the design and use of this technology, with two conceptual changes rolling through endodontic instrumentation today. The first is growing appreciation for tapered shaping objectives over the apical stop, and the second is the realization that we do not have to sacrifice dentin to clean root canals.

Rotary vs. hand files
Using handpiece-driven NiTi files to create traditional canal shapes is significant progress. Tapered resistance is more predictable than apical stop preparation because it is forgiving of length determination errors.

Compared with hand instrumentation, rotary is faster and more efficient, thus reducing stress for both the patient and the dentist. It allows for a cleaner canal extruding less debris in the periapical region.

However the way I practice, rotary instrumentation can never completely replace hand instrumentation. Probably 90% of the work I do is done with rotary instruments, but a very important 10% is still done manually. Those key steps are probing the canal and becoming familiar with its morphology.

Hand instruments are really extensions of your fingers, and the tactile sense is crucial in determining whether curves or blockages exist. With normal hand instrumentation, you can determine these situations at the beginning of treatment and proceed accordingly.There also are situations, such as extremely curved canals, where you might not want to use a rotary all the way to the root tip. Dr. Noah Chivian, Former President, American Association of Endodontists, agrees with me, adding “I always finish with hand instruments at the back end of every procedure as a final check.”

For hand instrumentation, dentists also use NiTi files that offer 500% greater flexibility than stainless steel. Combining this flexibility with a tapered file can effectively flare the coronal portion of the canal without creating a ledge or perforation.

With so many file types available, it can be helpful to understand the design and function of the instruments to know how the different systems are expected to perform. Here is a description and some opinions of a number of available file systems.

EndoSequence™ – Brasseler USA
The triangular shape of the EndoSequence™ files from Brasseler USA resembles a reamer, and its alternating contact points keep the file centered, increase its sharpness and reduce torque requirements, increasing efficiency. EndoSequence files are electropolished to remove imperfections that might lead to separation and cracking making them sharper, cleaner and more durable files, which will lead to better cutting efficiency.

The technique when using these files incorporates a laser-verified bioceramic-layered gutta-percha and bioceramic EndoSequence BC sealer accomplishing 100% hydraulic obturation that does not shrink or resorb in the canal. The restorative component completing the continuum is the final stage with a post exactly fitting in the preparation.

LightSpeedLSX – Discus Dental
What sets LightSpeedLSX from Discus Dental (discusdental.com) apart from the rest is that it is non-tapered. However, this doesn’t mean canals instrumented with this system aren’t tapered when finished-it just goes about it in a different manner. LightSpeedLSX is used by many dentists to conservatively prepare the entire length of the canal. For those wanting greater tapers along with excellent apical preparations, LightSpeedLSX can be “hybridized” quite efficiently in combination with other tapered NiTi instruments.

The advantages of a non-tapered instrument design are:

Better tactile feel

More flexibility

Superior apical debridement with conservative coronal enlargement

Added safety

Rendering canals clean is a main goal for endodontic success. Research has unequivocally indicated that canals prepared to larger sizes result in cleaner canals. Our objective is to clean the canal as best as possible, safely, avoiding ledging, instrument breakage and weakening the root by excessive dentin removal. The non-tapered design of LightSpeedLSX satisfies all these criteria and thus, in my opinion, offers a superior approach to apical instrumentation compared with other instrument designs.

ProTaper –
DENTSPLY Tulsa
Each of the instruments in the ProTaper series of files from DENTSPLY Tulsa (tulsadental.com) has multiple increasing and decreasing tapers from the tip over the length of the cutting blades. Progressively tapered design reduces the number of recapitulations needed to achieve length, especially in small-diameter or more curved canals. This design feature allows each shaping file to perform its own modified “crown down” work.

One of the benefits of a progressively tapered shaping file is that each instrument engages a smaller zone of dentin, which reduces torsional loads, file fatigue and the potential for breakage. Three Finishing files-F1, F2 and F3-have tip diameters of 0.20 mm, 0.25 mm and 0.30 mm, respectively. Additionally, F1, F2 and F3 have fixed tapers between D1 and D3 of .07, .08 and .09, respectively. The finishing files have variable diameters and tapers that blend the tapered shaped into the middle apical one-third of the canal allowing better irrigant flow and dense obturation.

Quantec™ System and K3 Files – Sybron Endo
The Quantec™ System rotary Files from SybronEndo (sybronendo.com) are available in variable taper from .02-1.2 mm. These sequentially tapered flexible NiTi files flare the coronal and midportion of the canal. SybronEndo’s K3 canal shaping files feature fixed tapers of .02, .04 or .06. The .02 tapered K3 files are in 15-45 tip sizes and the .04 and .06 tapered K3 files are in 15-60 tip sizes and 21, 25 and 30 mm lengths. K3 is characterized with asymmetrically placed radial lands of unequal width and unequal flute widths and depths preventing the file from acting like a screw.

Making a choice
There are now more choices than ever when it comes to choosing an endodontic instrumentation system. That’s both good and bad news. More choices are usually better than fewer choices, but this means investing more time sorting out the advantages and disadvantages of each to make the right choice for your office. Don’t fall into the trap of believing the most “popular” systems must be the “best” systems. Would anyone argue that McDonald’s makes the world’s best hamburgers?
This article just scratches the surface; yet, hopefully it will help you to create a short list of systems to give serious consideration. Perhaps the very best choice for you is a combination of two complementary systems.

The author recommends
Regardless of which system you choose, or even if you are satisfied with your present technique, give serious consideration to EndoSequence and its bioceramic sealing, nonresorbable and tissue-friendly materials. Good apical cleaning is difficult, yet most would agree that it is also the most critical part of the endodontic treatment process.
LightSpeedLSX excels in apical debridement, so if you are serious about apical cleaning use the instrument best designed for this purpose. In my opinion, there is no better way to clean the apical one-third than to debride with LightSpeedLSX, irrigate with EndoVac, “crown down” with EndoSequence and then hydraulically obturate with the bioceramic sealer.

Putting a choice into practice
Coronal instrumentation can be done successfully many different ways with many different instruments. When you choose a system to use, be sure to take a hands-on course, but consider these courses as just the beginning, not the end of your training. Use courses to get you started in the right direction, but then practice on more extracted teeth before you start treating patients.

I strongly suggest you also use extracted teeth to both practice a new technique and evaluate the results of your work to make an informed choice. By that, I mean radiograph the prepared and obturated tooth in both a clinical and proximal direction, and then take an extra step and cut across the root (cross-section) starting 1 mm from the apex. All it takes is a highspeed handpiece and smooth-cutting bur.

Cross-sectioning will reveal a lot about the instrument’s ability to do its job. Ideally, a well-prepared canal will look completely round, not oval, and will have a significant amount of dentin remaining all around it. While most systems can make the preparation look good on a clinical-view x-ray, use this cross-sectioning technique to separate the contenders from the pretenders.

Other simple steps you can take to implement a new system more easily and effectively include:

Begin with easier cases then gradually tackle more difficult cases as your skill and confidence increases. Go to the American Association of Endodontists website (aae.org) to check out its case evaluation and treatment selection form. This will help you determine when it is best to “hold ‘em or fold ‘em.” Very basically, any case that is going to take more than two hours of your time should be sent to the endodontist.

Schedule plenty of time to complete your first few cases until you and your staff become proficient with the technique. Sometimes you can arrange for a local representative or experienced dentist to help you through your first few cases.

Practice on many extracted teeth before treating patients. X-ray and cross-section them to ensure what you think is happening inside is actually happening. Involve your assistants in this practice as well so they too can be comfortable and proficient when you are ready to begin treating patients.

The products that appear in conjunction with this article are for illustrative or informational purposes only. Their inclusion does not denote endorsement by the author of this article.