Dr. Jeffrey W. Linden

FIGS. 1–2 Radiographs showing an endodontic case that required retreatment (Fig. 1, above). Radiographic evidence colored to highlight the discovery of anomalous pulp stones (Fig. 2, below).

“It has long been a bias of mine that what takes place before the root canal is started goes a long way to determining the quality of the end result. Dr. Jeffrey Linden has written a clinically relevant and concise piece to address many of the key concepts needed to guide the delivery of top level endodontic care.”-Dr. Richard E. Mounce, team lead

With any treatment protocol, dentists must achieve two concurrent objectives. They must deliver the highest standards of patient care, while at the same time-using the latest technological advances in dentistry-they must ensure treatments are accomplished efficiently and painlessly at a reasonable cost.

Fortunately, these two objectives are, more often than not, complementary. Maintaining high care standards is often far less costly, in both the long- and short-term, than treatment performed to lower standards. When viable bacteria remain in the root canal there is a risk of periapical infection. Many endodontic failures can be attributed to coronal leakage resulting from failed restorations. With the high frequency of apical periodontitis, the science reports retreatment including restoration and prosthetic replacement has hada huge economic cost of billions of dollars.

Diagnostics: Foundation of endodontic success


	Root canal therapy most likely will be successful if the canal is free of infection when obturated. The optimal approach is an accurate diagnosis to instrumentation strategies thoroughly removing tissue and shaping the coronal midroot and apex. The goals of root-canal therapy involve treating pulpal bacterial infection by removing infected tissues within the chamber, thorough cleansing mirroring the individual root anatomy and effectively sealing the tooth to prevent re-infection (Fig. 1). Careful diagnosis and cleaning of the tooth improves the long-term success rate of endodontic procedures and, at the same time, reduces the chances retreatment will be necessary.

Current negative pressure irrigation techniques such as the Endovac and thorough apical instrumentation with a system such as Lightspeed LSX, from Discus Dental (discusdental.com), are among the latest cleaning and shaping instruments. Additionally, the corded gutta-percha system, Obtura III Max from Obtura Spartan (obtura.com), and the cordless Hotshot from Discus make obturation easier and complete.

In today’s endodontic practice, we identify a number of techniques and therapies that improve practice efficiency and healing rate, either by enhancing outcomes, streamlining procedures, or both. Endodontists may disagree about the best way to fill root canals, but there is no dispute that the key to endodontic success is the complete removal of the microbes.

Identifying periapical pathosis and its management requires a complete clinical and radiographic exam. Apical periodontitis is inflammation of the surrounding tissues and the surrounding dentin at the root system’s portals of entry. Therefore, understanding the extent of the infection along with the overall structural soundness of the tooth is critical to ensuring the procedure will be both efficient and successful.


	Interpretation of a radiographic image is subjective and a learned skill regardless of the radiographic options we have today. Diagnosticians use oral x-rays and now innovative Cone Bean Computed Tomography (CBCT) systems as part of their armamentarium. But regardless of the imaging technology used, the epiphany comes from the diagnosis the image makes available and not the image itself.

Radiographs are a two dimensional view of a three dimensional phenomenon inconsistently showing changes of the clinical and biologic conditions. Off-angled films can enhance the diagnostic assessment of root canals including traumatic injuries, coronal, horizontal, and at times, vertical root fractures. Deviations on the mineralization and structure of the bone adjacent to the affected area enable us to potentially visualize calcifications and resorption.

Cutting edge digital radiography is basic for diagnosis and treatment. The addition of 

 and its ability to generate 16,000 shades of gray in 2.2 megapixel radiograph images provides for sharper image quality for visualization on a large monitor.

Anatomic anomalies and variations in the root canal shapes and space and occasionally pulp stones (Fig. 2) are identifiable on radiographs and CBCT scans. That said, canals are infrequently as straight as they may appear on a radiograph. They tend to be oval and irregular rather than round and regular, and typically present with a variety of curvatures, including deltas and bayonet shapes (Fig. 3) making instrumentation more challenging. An additional mesiobuccal canal is seen in Fig. 4, a mesial-angled radiograph of a mandibular molar with 5 canals.

Of course obtaining these images can be difficult, especially when a rubber dam in place in the patient’s mouth (noncompliance is not an option), makes positioning of the film or sensor even more challenging.

FIGs. 3–4 The roots on this radiograph have been colored to highlight the variety of irregular canal anatomies that are commonly found (Fig. 3, above). Teeth-such as this one with five-can have unusual numbers of canals. (Fig. 4, below).


	In addition to x-rays, there are several other diagnostic tests to identify the nature and extent of the bacterial infection. Vital pulp tests are essential components of the endodontic consultation. The hot and cold test, pulp vitality test (to check for failing pulpal blood circulation, not vitality), percussion, palpation for sensitivity and evidence of breakdown are all key in differentiating diagnoses.

In the process of making a diagnosis, an important step is to reproduce the symptoms of the patient’s chief complaint. This should be clearly explained to the patient for accuracy. The patient should understand in advance what to expect from the tests to maximize the value of the information obtained.

It should be emphasized that once pulp is stimulated with cold, there is a refractory period before a second cold or a hot test can be accurately conducted. More often, most endodontic tests are comparative tests; contralateral teeth and neighboring teeth should be tested for the contrasting normal responses. These vital pulp testing strategies enable the patient to appreciate the normal pulpal responses exhibited by asymptomatic teeth. Repeated testing reduces the probability of false positives or negatives.

For trauma cases, obtaining films taken prior to the injury is critical to proper diagnosis to gauge the progressive sizes of the lesion and provide appropriate treatment planning. In trauma and carious exposure cases in young patients with immature apices, the extent of the pulpal involvement and apical closure is of primary consideration. In cases where immature apices are affected, drug therapy with calcium hydroxide or mineral trioxide aggregate (MTA) can help promote apexification.

By obtaining a thorough diagnosis, endodontic procedures can be performed with as clear a treatment plan as possible, helping to reduce the incidence of surprises that may add time to a procedure. Therefore, a systemic approach to diagnostic judgment is key to prevent misinterpretation and mistakes. As stated by Dr. Richard E. Mounce, “Most of the clinical issues and challenges that bedevil treatment are foreseeable.”

With endodontics, the most efficient procedure is the procedure that is well planned and executed from the start. By properly diagnosing the condition of the tooth structures and thoroughly removing as much infected material as possible, the practitioner ensures the procedure will go smoothly with treatment to the highest standard. Success rates will be high-and that’s a strong foundation for any dental practice.

Dr. Jeffrey W. Linden is assistant clinical professor, Columbia School of Dental and Oral Surgery, Attending, St. Barnabas Hospital/Cornell Medical Center. An international lecturer on ultrasonic endondontics, Dr. Linden maintains a private practice in endodontics and endodontic surgery in New York City. He can be reached by calling 212-595-1161, or online at endonyc.com or jefflinden@earthlink.net.

Articles

Spotting the trouble: Successful endodontic treatment

“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.”-

	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.


	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.


	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.


	The triangular shape of the EndoSequence™ files from 

 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.


	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:

	Superior apical debridement with conservative coronal enlargement

	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.


	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.


	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.


	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.


	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.

 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