Inside Job

In the ongoing quest to effect as thorough a clean as possible when performing root canal therapy, endodontists are increasingly reaching for ultrasonic instruments. We consider their benefits and how you can parlay them into the kinds of sales that will take your customers’ practices to the next level.

Ultrasonic technology has long been a go-to instrument for dental prophylaxis and periodontal therapy. But it is also becoming a game changer for the inner tooth in root canal treatments (RCTs). Some even call it “endosonics,” a reference to the synergy between ultrasonic technology, instrumentation, and disinfection that has increasing numbers of endodontists reaching for this invaluable tool.

In fact, endodontists such as Allen Ali Nasseh, DDS, a Boston-based practitioner, and president and CEO of Real World Endo, which specializes in continuing education for dentists, count ultrasonics among their most important instruments. Says Nasseh. “If there’s one instrument that has greatly impacted my practice over the past two decades, it has been the ultrasonic unit, which I use on every single surgical and nonsurgical treatment.”

And many of today’s endodontists would agree. RCT is a multistep procedure that can be aided by ultrasonic technology. “For nonsurgical RCT, the ultrasonic is used to refine the access preparation, trough and find hidden canals while improving visualization and removing potential obstacles, including posts and separated instruments. It’s also useful for irrigation and activation of the irrigation fluids. For surgical cases, ultrasonics are used for the important task of retropreparation,” says Nasseh, adding that these tools allow room for cleaning, retrofilling and sealing the apex.


A tooth is divided into thirds: the coronal third, middle third and apical third. The first step in RCT is the creation of an access cavity in the coronal third, or crown, of the tooth. This involves cutting into the surface to access the pulp chamber. Because they cut efficiently via vibration versus rotation, ultrasonics can help clinicians to safely create an orifice so they can locate root canals.

Once canals are located, shaping and cleaning prepare them for obturation. Shaping smoothes canal walls, eliminating calcifications and other obstructive irregularities. Dallas-based endodontist and a past president of the American Association of Endodontics, James Gutmann, DDS, notes that ultrasonics can be hugely beneficial during this portion of the procedure. “The loosening and removal of tissue debris and pulp stones without gouging tooth structure, breaking up bacterial cell walls, removal of the smear layer that is created with enlarging and shaping instruments, enhancing disinfection of the canals and dentinal tubules, and breaking up biofilms all result in a much cleaner root canal preparation prior to obturation,” he explains. But the shaping process results in debris, which can’t be completely removed through mechanical instrumentation. Yet, its removal, and thorough cleaning and disinfection of canals, is paramount to RCT success. The ticket to this particular kind of root canal nirvana comes courtesy of irrigant agitation.


Ultrasonic devices operate via acoustic waves that operate above 20 kHz, which is the typical range that is audible to the human ear. But there is more than one kind of technology at play. Dallas-based endodontist James Gutmann, DDS, an endodontist and a past president of the American Association of Endodontics, explains, “Ultrasonics used for operative and preventative procedures are usually divided into two groups: magnetostrictive and piezoelectric. Both of these classes of ultrasonics are clinically well accepted in dentistry.”

Long used in the U.S., magnetostrictive ultrasonic units work by converting electromagnetic energy into mechanical energy. They do this by subjecting a stack of metal strips to a magnetic field, such as a live coil, which results in vibrations in the metal strips. This, in turn, causes the tip, which is active on all sides, to move elliptically in a range of 18,000 to 45,000 cycles per second, or 18 to 45 kHz. One problem with magnetostrictive ultrasonics is heat creation. Unfortunately, heat can damage dentition. Therefore, large amounts of cooling water are needed — so much that patients might complain that they are “drowning.” On the plus side, many magnetostrictive inserts are not brand limited, broadening the choice of inserts and suppliers.

Piezoelectric units generate very little heat, and therefore require less water for cooling. This makes them more comfortable for patients, although, ironically, some may complain of cold sensitivity because piezoelectric units don’t typically heat the water. While this unit has traditionally enjoyed more popularity in Europe and Japan, the piezoelectric unit is steadily gaining traction in the U.S. In this technology, crystals are exposed to an electrical charge, which causes them to deform. During this process, they generate energy that passes through a transducer in a handpiece, which then exits in the form of oscillations. Piezoelectric tips transfer most of their energy onto their lateral surfaces, oscillating in a back-and-forth, linear fashion, at anywhere from 25,000 to 50,000 cycles per second, or 25 to 50 kHz.

Gutmann says that the piezoelectric ultrasonic, first introduced to the market in the 1970s, is more conducive to endodontic use. “Since that time,” he says, “there has been an evolution in the technology, operation, ergonomics, and the design of the machines.”

Robert Roda, DDS, an endodontist practicing in Scottsdale, Arizona, and also a past president of the American Association of Endodontists, notes that most of the systems available for modern endodontic applications are piezoelectric instruments. “These allow for precise control through a wide range of power levels. I have not heard of a magnetostrictive unit being used in endodontics. Mostly they are used for removal of clinical calculus in periodontal applications.”

Nasseh agrees. “While magnetorestrictive units are adequate for basic dental hygiene and cleaning procedures, when it comes to endodontic therapy, a piezoelectric unit is necessary. The latter allows the correct tip motion oscillations that allows for especially designed tips to remove dentin effectively.”


Although it’s widely accepted that root canals cannot be sterilized, a critical part of performing RCT involves irrigation. Commonly used irrigants include chlorhexidine gluconate, sodium hypochlorite (NaOCl), ethylenediaminetetraacetic acid, and a mixture of a tetracycline isomer, citric acid and detergent. Irrigants provide lubrication for instruments during the shaping process, but they can also be bacterial agents used to help cleanse canals, dissolving or flushing out debris. The goal is to clean and disinfect canals as thoroughly as possible prior to obturation.

This is why ultrasonics is the best choice for endodontic applications, according to Richard Paschke, founder and managing director of Missoula, Montana-based Paschke Ultrasonix, which specializes in the design and development of ultrasonic devices and methods of manufacturing. “The high-frequency actions of the activated tips provide better penetration of the irrigant,” explains Paschke. “Acoustic streaming also facilitates cleaning of root canal isthmuses and lateral canals.”

Indeed, evidence shows that irrigant agitation heightens the cleaning effect through acoustic streaming, and drives fluids into complex areas that instrumentation may have missed or been unable to reach. Robert Roda, DDS, an endodontist practicing in Scottsdale, Arizona, observes, “Without ultrasonics, these spaces would remain as possible sources of persistent infection that could compromise the success of root canal therapy.” A past president of the American Association of Endodontists, Roda adds that the use of this technology is also immensely supportive of the concept of minimally invasive dentistry. “Older methods of finding these hidden spaces in the teeth (like using drills or burs) resulted in removal of so much tooth structure that weakening or even perforation of the root was a common occurrence.”

Nasseh agrees, noting he uses particular tips to find calcified canals deeper in the root instead of a rotary instrument. “The ultrasonic is minimally invasive and safer due to less aggressive cutting compared to a bur,” says Nasseh.

Among the techniques used to agitate irrigants, passive ultrasonic irrigation (PUI) is probably the best known. It involves placing the irrigant through a syringe or through injection by the operating system, which is then agitated by a tip file or a smooth instrument that is not being used to simultaneously instrument the canal.

Another technique is continuous ultrasonic irrigation (CUI). In this technique, an ultrasonically activated tip continually receives irrigant into the canal, allowing continual replacement of solution during instrumentation. Says Paschke, “There are challenges in CUI, but some literature supports the claim that it is statistically superior to PUI.”1


Ultrasonic is Minimally Invasive and SaferUltrasonic units would be nowhere without tips. And thanks to their broad range, endodontists can use this technology inside root canals to up their odds of success. Also referred to as “inserts” or “ultrasonic insert/tips” (UITs), they are available in many sizes and configurations to address various intraoral locations and adapt to dental anatomy, such as tooth curvatures.

Paschke says it’s important to keep in mind that instruments are application specific. For instance, he says, “In piezo, a top-down strategy is used to maximize treatment efficacy. This means the coronal third is debrided first, the middle third next and the apical third last. Therefore, the diameter of the instruments used for the coronal third are larger, and the instrument diameter is decreased for debridement approaching the apical third. It is important to note that different piezo manufacturers use different threads for their devices and tips. Therefore, one must determine tip compatibility with the equipment being used. Operational compatibility is also a concern. Tips designed by one manufacturer may not work optimally in another manufacturer’s system, even with tip compatibility.”

Gutmann notes that tip design options include smooth tips, serrated tips, and diamond tips. “The key,” he explains, “is the generation of activity in the canal that helps to achieve the benefits.” Ideally, each tip has its own ideal frequency and machines modulate the frequency based on the tip used. “A good ultrasonic machine must adapt to several unpredictable clinical conditions and tooth anatomy,” Gutmann says. “The most important feature of any ultrasonic unit is how it maneuvers the tip and adjusts to many different tip designs, each with a unique, intended function.”


Tips are often included in kits offered for dedicated armamentariums. And manufacturers will frequently recommend tips for particular applications. “Each ultrasonic unit and manufacturer has their own set of de­signed tips to do various procedures. They all try to do the same things but with slight design modifications,” says Nasseh, who favors those with LED lights to enhance visualization, which is especially useful in finding canals. He also likes that there is a range of sizes. For instance, among his favorites are tips that offer universal use for access refinement and those that are a little thicker to accommodate larger access openings. “The 
nondiamond-coated versions of the same tips can be used for both removal of posts, as well as irrigation throughout the procedure,” explains Nasseh. “Lastly, I use tips with U file inserts at the very end of the procedure to agitate and activate my irrigation solutions for more effective removal of the smear layer and disinfection prior to obturation.”

In Roda’s estimation, two tips are useful in the canal space. “The flat-ended or football-shaped tips are generally a bit larger and are used to uncover hidden canal orifices or excavate severely calcified roots to find canals,” he says. “Long, tapered, sharper-tipped instruments are mainly used for dislodging blockages and for gently excavating the lateral walls of canals to clean fins or grooves. A variant of the long, thin tip has a blunt end and is used for irrigant activation.”

Point of Sale | Benefits of Ultrasonics in Endo

  • Ultrasonic devices are upping the odds for endodontic success through safe, precise cutting.
  • Ultrasonic agitation of irrigant has proven to be highly beneficial in ensuring that even the farthest reaches of canals are cleaned and disinfected.
  • Piezoelectric units have the most to offer for endodontic applications.
  • Use of ultrasonics in endodontics supports the concept of minimally invasive dentistry

Tips are constructed from a variety of materials. Says Gutmann, “Dental manufacturers have brought us a variety of tips and cutting surfaces such as smooth stainless steel, zirconium nitride, and diamond-coated tips.” Some tips are designed specifically for microsurgery. “Ultrasonic instruments have been in regular use in microscopic endodontics for more than 25 years,” says Roda. “The ultrasonic energy is applied to a tiny tip that allows microscopic manipulation of tooth structure and materials in the root canal spaces. Ultrasonic tips can be used to excavate minute amounts of tooth structure in a highly controlled manner to help discover tiny openings into canal spaces to for cleaning and disinfection.”

According to Roda, the use of ultrasonics generally requires magnification. “If clinicians are using loupes and headlamps, they will be severely limited in the tasks they can accomplish using ultrasonics. The use of the dental operating microscope with ultrasonics opens up the full possibilities of this amazing instrument.”


Acoustic streaming: The circulation of fluid in close approximation of a vibrating tip.
Apical third: The portion of the root canal that lies at the tip.
Cavitation: The violent implosion of gas-filled bubbles, which results in a shock wave to dislodge intracanal material.
Coronal third: The crown portion of a tooth.
Middle third: The portion of the root canal that lies between the coronal third and the apical third.
Retropreparation: Root end surgery.
Trough: To open the floor of the pulp chamber to reveal canals.<

Overall, most clinicians appear to agree on the safety and efficacy of ultrasonic instruments. And, in the long run, the use of these tools in endo­dontics will help ensure the continued success of inside jobs.




  1. Adcock JM, Sidow SJ, Looney SW, et al. Histologic evaluation of canal and isthmus debridement efficacies of two different irrigant delivery techniques in a closed system. J Endod. 2011;37:544–548.


From MENTOR. October 2017;8(10): 18, 20, 22-23.

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