by Kenneth Koch, DMD, and Dennis Brave, DDS
The "Real World" endo guys offer clinical tips on using ultrasonics in general practice.
If you perform endodontics, and wish to do it in a profitable manner, the addition of an ultrasonic is something that will benefit you greatly. We feel very strongly about that statement. Ultrasonics offer many advantages, but first, we need some definitions. We have evolved in endodontics from sonics to ultrasonics to now — piezo electric ultrasonics. In modern endodontics, when we talk of ultrasonics, we really mean piezo electric ultrasonics. We prefer them, as compared to the earlier magnostrictive units, for two reasons: Piezo electric technology offers more "cycles" per second (40,000 CPS versus 24,000 CPS), and secondly, the tips of these units work in a linear, back-and-forth "piston-like" movement. Its motion is ideal for endodontics. This is particularly evident when removing posts and separated instruments. Additionally, in surgical endodontics, this motion is ideal for creating a retropreparation. The earlier, magnostrictive type of unit produces more of an elliptical or figure-8 motion, which is not ideal for endodontic use.
We are always amazed, however, at the number of dentists who think ultrasonic use in endodontics only has a surgical application. This is not true. It is likely that 90 percent of all ultrasonic use is in nonsurgical endodontics. Piezo ultrasonics have five significant nonsurgical applications.
Increased efficacy of the irrigation agentWe all know the adage, "instruments shape, irrigants clean." But how can we make our irrigation more effective? Simple. By placing an ultrasonic tip into the bleach that is in the chamber, we can enhance the cleaning efficacy of our irrigation agent. This is because the ultrasonic creates both cavitation and acoustic streaming. The cavitation, which is like the action created by a boat propeller, is minimal and is restricted to the tip. The acoustic streaming effect, however, is significant. The only way that you can effectively clean webs and fins is through movement of your irrigation agent. You cannot mechanically clean these areas. Ultrasonics are a great help in cleaning these difficult anatomical features. If we are going to fill root canal systems three dimensionally, we must clean them in a likewise manner. Research has shown that the cleanest canals are those that follow instrumentation with a brief period of ultrasonic cleaning. Interestingly, it does not seem to matter if the time of ultrasonic streaming is one minute or three minutes.The technique itself is quite simple: Choose a basic spreader tip, turn off the water (if necessary) and place the tip into the irrigation agent. You will notice lots of effervescence (bubbles). After about 20 seconds, you will evaporate the solution. However, what has taken place is extensive streaming of the irrigation agent. Replenish the solution and repeat for another 20 seconds. Repeat this procedure for a minute or until you no longer see debris floating up from the canals. This is particularly effective on C-shaped canals. C-shaped canals have large fins that hold excessive amounts of tissue. Ultrasonics are a tremendous help in cleaning these cases.
Finding canal orificesIn addition to length control, the biggest challenge facing the general practitioner is finding the canals, particularly in those cases where the orifice has become calcified secondary to restorative materials or a pulpotomy. You cannot perform a root canal unless you find the orifice. Piezo electric ultrasonics are excellent for removing the secondary dentin that often slopes off the mesial wall. This is what occludes the MB 2 canal. Ultrasonics also perform well when breaking through the calcification that covers the canal orifice. A good tip choice for this task is the CT-4, which is a troughing tip. As a result of the "graying of America," along with the increased popularity of posterior resins, we are seeing more coronal calcification. If you treat geriatric patients, the solution is obvious. You need to have a piezo electric ultrasonic. The advantage is significant.Removing posts and coresGeneral dentists can and should be doing some re-treatment cases. Many of these cases will involve removal of a post. There are many expensive gadgets available that supposedly remove posts. Unfortunately, some of these don't work as well as advertised. Furthermore, some of them have problems with freeway space in the posterior part of the mouth. Post extractors should only be used as a last resort. We prefer to remove posts with an ultrasonic. Ultrasonics are a tremendous help in post removal. Here are some tips you should know:•When removing a post, it is critical to break the seal between the post and the tooth structure. This can be accomplished with a surgical-length No. ¼ round bur. This is technique-sensitive, so be careful that you are going along the long axis of the root. Once you have trephinated around the post, you can place an ultrasonic tip into the trough. A basic spreader tip will do fine. This will further break the cement or resin, and you will notice motion in the post.
•An alternate way to break the seal is to initially use a spreader or troughing tip. Sometimes you can place a spreader tip against the post itself. This works well if the seal has been broken.
•Another option is to clamp the post with a hemostat and then vibrate the hemostat with an ultrasonic tip. However, do not clamp the post directly with a hemostat and then try to "muscle it." In the past, some dentists would try this and they would hear the cement crack — bad idea. With the new, stronger anaerobic resin cements, if you "muscle" a post, and hear a crack, guess what? You just cracked the tooth. Take your time, don't panic, and the post will come out.
•Also, we strongly recommend using spreader tips with water spray. If you run a spreader tip dry, a couple of things happen, none of which are good. For one thing, the handpiece on some units becomes very hot and the ultrasonic tip gets overheated. Secondly, the post becomes heated and this heat can eventually be transferred to the periodontal ligament. Lastly, when using an ultrasonic without water spray, you will have an increased smell of burning dentin. Nice, huh? These dilemmas can be avoided through the use of an ultrasonic tip with a water port. If you want to use the ultrasonic "dry" for a few seconds, simply turn off the water. More importantly, the water is there when you need it.
Removing broken instrumentsPiezo electric ultrasonics are excellent for removing broken instruments. However, you must be aware of the differences in removing separated hand files as opposed to rotaries. If a rotary file is separated past the canal curvature, this will be extremely difficult to remove. Don't fall prey to those "experts" who cavalierly say, "I just pull over my microscope and remove it." These are difficult cases. On the other hand, broken instruments in the coronal half of the canal can be removed in a straight-forward manner. Be honest with yourself, however. If you do not have the experience or necessary magnification, you may want to refer this case. When removing a broken instrument in the coronal third, a thin spreader tip will work nicely. Most ultrasonic companies have tips specifically designed to remove broken instruments. Take the tip into the canal and work it in a counter-clockwise motion around the broken fragment. This will dislodge the broken instrument. Stainless steel hand files often will float out of the canal with the water spray. Removing silver pointsSilver points were placed for many years, and we still re-treat many teeth that have silver points. Silver points are basically round, while most canals are somewhat oval. Consequently, leakage is a problem with a number of silver point cases, and flare-ups are more common than with regular gutta percha cases. The incidence of flare-ups is related to chronic leakage and corrosion products. The key point when removing silver points is to realize that silver is a very soft material. Any misdirection with a bur will sever the point, rendering the case more difficult. Ultrasonics are a huge help in removing these points. Simply trough around the silver point with an ultrasonic spreader tip. Carefully follow the long axis of the point; do not cut the point. The vibration generated by the spreader tip will quickly loosen the silver point. Simply grab the point with a Steiglitz forceps or hemostat and remove. It's a straight-forward operation — if you have an ultrasonic.Miscellaneous uses
Piezo electric ultrasonics have a host of other indications. For example, poorly-fitted crowns can be loosened by placing a vibratory tip against its buccal surface. Another indication is with MTA. Place a K file into the MTA and then place an ultrasonic tip against the file. The vibration will move the MTA down the canal and into the perforation. When re-treating "metal carrier" cases, an ultrasonic can be helpful. Turn the water off and run the ultrasonic dry. It becomes quite hot. Place the hot spreader tip against the carrier for a period of 10 to 12 seconds. The carrier will become hot, and will plasticize the gutta percha down in the canal. Simply remove the carrier and re-treat as a regular gutta percha case. The preferred way, however, is to heat the carrier with a Touch 'n Heat or System B. Also, do not forget periodontics and hygiene. Many periodontists have embraced piezo electric ultrasonics, and if your unit has optional alternate periodontal scaling tips, we recommend buying them. You want to have at least three, preferably four, perio tips.
There is a good selection of piezo electric ultrasonics and assorted tips available. We recommend that you evaluate multiple units before making a purchase. Some of the quality piezo units are: Spartan MTS, Satelec Suprasson P-5, EMS Piezon Master 400, Osada Enac, and the Analytic miniEndo II. Also, there are new, third- generation units coming to the marketplace.
One of the more interesting units is the new EndoExact ultrasonic by SybronEndo. This unit has new software that continuously recalibrates a wider range of power options than their previous miniEndo.
The wider power range means a more powerful machine for quicker post removal, as well as a "kinder, gentler" unit for periodontal applications. Moreover, the EndoExact features a patented feedback system that tunes the amplitude and frequency of the unit depending upon the tip load. This is very important as this new technology will result in more precise control of tip dynamics.
As previously mentioned, in addition to having a good ultrasonic unit, you need to have a good selection of tips. All the listed units have a series of tips associated with their product.
Do not use ultrasonics to instrument canals. In our opinion, ultrasonics or sonic-driven instrumentation is too aggressive. We feel that rotary instruments are a much better alternative. Ultrasonics are, however, a tremendous help in cleaning the root canal system. Use your ultrasonic as an adjunct to your endodontic treatment. Take advantage of the benefits offered by piezo electric units.
Just a few observations about tips:Spreader tips or similar designs are extremely effective in removing broken instruments. Some of the tips, specifically designed to remove instruments, are very thin and fragile. Be careful to run these at the proper intensity and don't break them. Always read the instructions concerning the correct power intensity.Choose tips that have a good track record. In other words, use tips that do not have a tendency to break. On a personal note, we have found Dr. Gary Carr's tips (CT series) to be extremely reliable. Also, the "KiS" tips, designed by Dr. Syngcuk Kim, are terrific. The "KiS tips" are used mainly for surgery.
If possible, try to use tips with a water spray. Sometimes, under a microscope, you may wish to have increased visibility, and therefore, choose to turn off the water for a brief period of time. Sometimes, however, we purposely place water into the canal, as this acts like a prism and allows us to see behind the tooth. Generally, you will find that ultrasonic tips work much more effectively with a water spray. An example of this are the CPR tips by Spartan/Obtura. They took a good tip (zirconium nitride-coated CPR without a water port) and made it an excellent one — diamond-coated CPR with a water port. Additionally, the new diamond tips by SybronEndo are well-designed and come equipped with water ports.
Vibratory tips have a very limited use. They can help to remove crowns but only poorly-fitting crowns. You will not have much success trying to vibrate off well-done units. Also, never place a vibratory tip against a porcelain crown. Not only will you craze the "glass," you have a good chance of fracturing the porcelain. Use these tips on metal crowns only.
Ultrasonic tips are available with different coatings such as zirconium nitride or diamond. Also, plain stainless steel tips available for ultrasonic use. There are proponents for each of these different coatings. Consequently, our recommendation is to try a few different types and decide what works best in your hands.
