Written by Arthur K. Weathers, DDS Thursday, 01 January 2004 00:00
Welcome to this series of articles on endodontics, which I've chosen to call "Access to Success." There are 2 senses in which the phrase "access to success" can be taken. Let me start with the endodontic meaning: access is the first step in doing a root canal procedure, and it's one of the most critical aspects of endodontic therapy. If you successfully prepare the tooth you're working on to give yourself proper access to the root canal system, you're improving your prospects for success immeasurably.
Second, by improving your endodontic skills, you're giving yourself access to success. You're learning and perfecting techniques that will enable you to grow your practice by expanding your knowledge base in one of the fastest growing and most profitable areas of dentistry today.
Whether you're someone who's new to endodontics and wants to learn the safest and most efficient ways to perform root canal procedures or a veteran who'd like to polish your skills, this series of articles will bring you up to date on the latest techniques and technology that are streamlining the process of performing root canal procedures and making it efficient, safer, and productive.
"TOO SMALL" CAN BE A "BIG" PROBLEM
Let's start with a working definition of the term access. Access is creating the means by which we locate and identify root canals and remove diseased pulp. But my definition of access goes further than most. You've achieved adequate access—by my standards—when the roof of the pulp chamber is fully removed and you have straight-line visual access to all the canals. The first principle of good access is making an opening that is large enough to allow you to see all of the root canals at the same time.
|Figure 1. Inadequate access.||Figure 2. Good access—all canals visible.|
I've had the opportunity to observe and critique thousands of dentists at our hands-on "Root Camp" seminars, and one of the most common problems I see is seminar attendees not creating an adequate access opening. The purpose of this article, then, is twofold. First, I want to take you step-by-step through the procedure for creating ideal endodontic access. Second, and equally as important, I want to show you how to avoid making the most common access mistakes so that you can make each step as efficient and safe as possible for your patients (Figures 1 and 2).
|Figure 3. Canal Projectors in place.||Figure 4. Step 1: Create an endodontic access cavity as described above and dimple all orifices with a No. 2 slow-speed round bur to approach "straight-line" access. Apply an appropriate matrix band, then acid-etch and prime.|
|Figure 5. Step 2: Place Canal Projectors on endodontic files and slide them upwards toward the file handles. Work the Projectors on the files in short vertical strokes to ensure free movement on the flutes.||Figure 6. Step 3: Insert a file with a Projector well into each canal. I recommend using different sized files to facilitate identifying the canals.|
|Figure 7. Step 4: With a cotton plier, slide each Projector apically until it seats precisely into the dimple previously created (refer to Step 1). Place bonding agent on the cavity floor and pulp chamber walls, and distribute it evenly over primed surfaces with air blast.||Figure 8. Step 5: Inject an appropriate auto-polymerizing material such as composite or glass ionomer into the chamber, injecting it from the bottom up to avoid trapping air bubbles. Note that most core materials are too viscous for injection into tight areas.|
|Figure 9. Step 6: Make certain the file handles are in desired alignment. Note that in some cases it may be helpful to use an instrument to separate the file handles as the projection matrix polymerizes, ensuring that projected orifices will be conveniently oriented on the cavo-surface.||Figure 10. Step 7: At an early stage of polymerization, work the files in several short vertical strokes, then carefully remove them.|
|Figure 11. Step 8: Flatten the surface of the polymerized projection matrix and the coronal portion of the imbedded Projectors using a high-speed, bull-nosed diamond.||Figure 12. Step 9: Remove Projectors by inserting a No. 60 or larger Hedstrom file, rotating it to engage the flutes in the lumen of the Projector. You may soak the Projectors in NaOCL and reinsert them as part of the temporization process. Simply cut off a millimeter or 2 from the top of each Projector, reinsert, and cover with your temporary material. At the next appointment, it's easy to locate the Projector beneath the temporary and withdraw it using a No. 60 or larger Hedstrom file.|
|Figure 13. Step 10: Proceed with the remainder of your endodontic therapy.|
THE RIGHT STUFF
Among the key things you'll need to perform successful root canal procedures are the right tools, including the following:
Digital Radiography Equipment
Notice that I've specified a "digital" x-ray system, and that I've put it at the head of this list of tools. Because it saves so much time, is so effective as a diagnostic tool, and significantly reduces patient exposure to radiation, it's difficult for me to think about doing a root canal procedure without my Dexis digital imaging system. I recommend that you take at least 2 radiographs from 2 different angles before beginning any root canal and that you take multiple images as you're performing endodontic therapy. I will discuss digital imaging in part 2 of this series.
Burs and Drills
Minimally, you'll need a No. 4 round bur and an Endo Z bur (DENTSPLY Maillefer), but I also find No. 2 round and No. 6 round burs useful on many occasions. You'll need to have a variety of files available, including Peeso reamers and Gates Glidden drills, as you perform root canal therapy.
I recommend that you use a rubber dam in every root canal procedure you perform. I've got a few cautionary words about rubber dams, but I find that they're an indispensable tool for increasing efficiency and helping reduce potential complications.
Illumination and Magnification
You'll find a fiber-optic illuminator very useful in performing root canal therapy. I'll explain how you can use this tool to confirm your identification and location of the canals.
Size 0 Mirror
When performing endodontic procedures, you'll find that things can get pretty crowded inside your patient's mouth, especially when you have 3 or 4 files protruding from a single access opening. For this reason, I recommend that you consider a size 0 mirror (Thompson Dental Company).
In creating adequate access, the goal we're working toward is what I term visualization. By that I mean that when you've finished creating your access opening, you should be able to see clearly all the root canals with one eye closed. I'll discuss this further as we get into the technique section of this article.
I hope I've managed to convey the importance of creating an access opening that is large enough so you can perform a root canal safely and efficiently. As I mentioned when I was discussing visualization, the way you know if an access opening is adequate is that you're able to see all the root canals with one eye closed and without moving your head or the mirror. I emphasize the fact that you've got to be able to see the root canals without going through any contortions because if you have to move around to gain visual access, you're very likely going to have problems getting files into and out of the canals without bending and breaking them.
Creating an access opening that satisfies this critical requirement may involve removing part or all of one or more cusps. You should not hesitate to do this. Many dentists, motivated by a desire to be "conservative" about the amount of tooth structure they remove while creating an access opening, make the access much too small to locate the canals easily and safely. I've never heard of a dentist who regretted having made too large an access opening after performing a successful root canal treatment. I have known many dentists, however, who have missed canals or perforated pulpal floors while unsuccessfully looking for canals in a poorly accessed tooth. The new generation of dentin bonding agents and composites that are extremely strong and aesthetically pleasing minimizes the importance of being conservative in creating an access opening to preserve tooth structure.
"DE-ROOFING" THE PULP CHAMBER
Your objective should be to create a flared opening. You want to avoid creating an opening that is "undercut;" you want to create an opening in which the entire top of the pulp chamber is removed, one which has gently flared or curved corners to guide the files into the canals.
The first step in creating an access opening is to "de-roof" or remove the top of the pulp chamber. For this I normally use a No. 4 round bur, although you may want to move up to a No. 6 or down to a No. 2, depending on the size of the tooth you're working on. In doing this, you'll want to avoid touching the floor of the pulp chamber so that you don't perforate the chamber floor or disturb the natural depressions that slope down to the root canal openings.
After you've penetrated the chamber roof, use an "upsweeping" motion to remove it completely. Note that in maxillary molars, you'll usually find a little "lip" of dentin at the chamber floor where the MB2 canal actually begins. You should carefully remove this dentin lip in order to ensure that you have proper access to this canal.
You can tell when you've created an adequate access opening by testing the canals with files. You should insert a file into each canal, letting it slide in naturally and not forcing it. If a file doesn't go into a canal readily, you may need to remove additional material from the coronal aspect of the canal. Let me give you an example of how this works, using a bicuspid with 2 canals for reference. If you insert a file into each of the canals, the files should go straight in and the handles should protrude nearly parallel to each other. If they cross, you have not removed enough coronal material, and you face potential file breakage as you're cleaning out the canals.
Treating lower anterior teeth provides a good example of a case in which you shouldn't hesitate to remove tooth structure in order to create an adequate access opening. I sometimes create a buccal access opening in order to get straight-line access to the canals in lower anteriors. Two canals are frequently found in this tooth, and a buccal access opening, which is easily restored with modern composites, will help ensure that you don't miss that elusive, lingual canal. You should also remove the mesio-buccal cusp when treating molars, since the mesio-buccal canal typically lies directly beneath this cusp. I also recommend that you reduce occlusal height in this case.
There are certain conditions where you can be somewhat more conservative. On an upper molar, for example, the mesio-buccal canal is immediately under the mesio-buccal cusp, but the disto-buccal canal is normally in the center of the tooth. In this case, you don't need to remove the disto-buccal cusp or the transverse ridge to gain adequate access.
For cases in which the tooth you're working on will be fitted with a crown, you should reduce the occlusal surface of the tooth prior to making your access opening. This will allow you improved visibility and will greatly reduce the possibility of having cusps cracked off during treatment. In addition, when you flatten the tooth surface, you're giving yourself a reference point for measuring root length and reducing the possibility of hyperocclusion between appointments.
With the access opening created, your next step is to identify and locate the canals. Fiber-optic illumination is an excellent aid in this process. Transilluminate the tooth by shining the light on its buccal or lingual surface, not directly into the pulp chamber. Illuminating the tooth from the side will cause the pulp chamber to "glow" and the root canals to appear as dark spots. I prefer the inexpensive Oral Lite from EndoSolutions for transillumination.
The first general principle in identifying canals is that you should suspect 2 canals in each root until you have positive proof that there is only one. On your diagnostic radiographs, if a canal appears fuzzy or out of focus about halfway down and then appears in sharp focus farther down, you have a good indicator that the canal has divided and rejoined itself. Also remember that in the case of teeth, "nature loves symmetry." If you locate a canal in any tooth that is not centered relative to the root, you should immediately look for a second canal.
There are also a number of special cases you should be aware of when you're locating root canals. The distal canal on lower molars is normally about twice the size of the mesial canals. This means that if you can fit a No. 15 file in the mesial canals, you should be able to fit a No. 30 file in the distal canal. If the No. 30 file won't fit in the distal canal, it's likely that there are 2 distal canals. Again, also apply the general principle I mentioned earlier: if the distal canal is not in the center of the root bucco-lingually, you should also suspect that there is a second canal.
For maxillary molars, the palatal canal is easiest to locate. You should look for it first, then look for the mesio-buccal canals, which will be buccal and mesial in relation to the palatal canal and usually be directly under the mesial-buccal cusp. In most cases, you may actually have to remove the entire mesial cusp in order to find the mesio-buccal canal.
Upper molars frequently have 2 canals in the mesio-buccal root. The second canal is usually lingual and slightly mesial to the main canal, although it may occasionally be located on a straight line between the mesio-buccal canal and the lingual canal. Lower bicuspids are often the most difficult teeth to treat endodontically. They frequently have multiple canals, and many practitioners refer them to specialists.
Canal Projectors can facilitate creating adequate access and preparation of root canals, especially in difficult cases. One can be slid onto an endodontic file and positioned at the entry of the root canal, where it is surrounded with self-polymerizing material such as composite or glass ionomer. When it's installed, it literally allows you to "project" the canal orifices from the floor of the pulp chamber to the cavo-surface, so you can visualize and access the canals easily. Using a Canal Projector is especially helpful in cases of severe coronal breakdown, tipped and/or rotated teeth, patients who have difficulty opening their mouths wide enough, and where the canal orifices on the pulp floor are close together. Figures 3 through 13 demonstrate the clinical technique for using Canal Projectors for improving access to root canals.
Once polymerization is complete, remove the file(s) and the projector(s). You'll have created a cone-shaped orifice that is easy to see, easy to access, and guides the tip of the endodontic file into the canal while helping keep files separate from each other. You can use Canal Projectors in multiple orifices simultaneously. Using Canal Projectors takes only about 3 minutes, and it can reduce treatment time by as much as 50% in certain cases.
RUBBER DAM: TIMING IS EVERYTHING
You'll notice that I haven't mentioned using a rubber dam up to this point. That's intentional. I've found that, while dentists should always use a rubber dam when performing root canal therapy, it's prudent to wait until the right time to install it. There's nothing more embarrassing or difficult to do than explain to your patient that you anesthetized tooth No. 24, then installed a rubber dam and began opening up tooth No. 25. It's not only tough to explain, it also means you get to perform 2 free root canal procedures. (And it might mean that you've involuntarily contributed to the patient's children's college fund if he or she wants to take you to court.)
It could happen. It's so much easier (and less expensive) to wait until after you've anesthetized and opened up the correct tooth to apply the rubber dam that I recommend you don't even think about doing it in reverse order. I'll explain how to place a rubber dam on any tooth in 10 seconds or less in part 2 of this article. In the meantime, keep the "dam" thing out of there until you've created your access opening.
In addition, any tooth that has been orthodontically repositioned or has been restored with a crown, veneer, or bonding may have an altered relationship between the crown and the root. With a rubber dam in place, it's frequently difficult to be certain of the correct angle to access the pulp. And in case you find that a tooth is still sensitive as you begin your procedure, it's much easier to re-anesthetize it without a rubber dam in place.
Finally, I prefer placing the Projectors with the rubber dam in place, but sometimes in a badly broken down tooth, the Projectors are placed to create something to hold the rubber dam clamp.
THAT'S A WRAP
I know you'll find the tips and procedures I've discussed in this article helpful as you strive for maximum success in your endodontic therapy.
In part 2 of this series, we will discuss how the rubber dam, digital imaging, and the electronic apex locator combine to help you isolate the tooth and determine ideal root canal working lengths.
Dr. Weathers has informed and entertained audiences of dental professionals for more than 30 years. He pioneered a simplified system of nickel-titanium files to enhance patient comfort with a 1-visit endodontic procedure. His methods have significantly improved dental efficiency and profitability as well. The "Level I and Level II Hands-on Endodontic Root Camp" seminar series, which Dr. Weathers hosts from his own multimedia learning center in Griffin, Ga, as well as from the Las Vegas Institute (LVI) for Advanced Dental Studies, offers multiday hands-on training to improve dental techniques while explaining his theory of "Endonomics," the economics of endodontic case management. Dr. Weathers is the editor of the DentalMagic! newsletter and the author of numerous articles on innovations in endodontic treatment products and processes as well as intraosseous anesthesia delivery systems. He also introduced the well-reviewed C.E.Magic! "edutainment" interactive learning system to the field of continuing education in dentistry. He can be reached at (770) 227-3636 or visit ce-magic.com.
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