Whatever you do, it’s important to know why you’re doing it, and what its strengths and limitations are. So here’s a little history of endodontics and why I’m doing what I’m doing currently.
Dentists should all know hand instrumentation, and the classic lateral condensation that usually accompanies it. The hand file systems are usually a .02 taper system with a variable file size, using a step-back technique. The result is a narrowly tapered canal, with an imperfect .02 rate of taper. Hand instruments do not machine the canal walls, they are simply made to scrape away pulp tissue and some necrotic dentin of the canal walls. Having a taper of .02 is less than ideal, because this almost parallel preparation makes it hard to 1) deliver adequate irrigation throughout the entire canal system and 2) achieve the best possible apical seal. Still, I’m not a hater of hand instrumentation, and I usually use it in conjunction with rotary. Nothing beats hand instruments for finding the apices of unusual canal systems, or apically bifurcating canals. Every case should start with an 8 or 10 hand file to establish a common pathway for your rotary files. I also like to use an apex locator, and hand files help with that. You also need to take a mid-operative file x-ray to verify length and see any weird curvatures. Hand files also help with recapitulation between rotary files in series; cleaning out debris and irrigating to maintain a pathway to the apex. Rotary systems are sold to us as having simplicity, but to simply start drilling on a crown-down technique without having a reproducible pathway to the apex is trouble. Also, if I have a canal that has more than 1 curve, (s-shaped instead of c-shaped), then that canal will need to be opened apically by hand. You can’t spin a rotary file into an s-shaped canal, it will break. Nothing will ever beat the fine touch that hand instruments allow. You can often feel the apex with a hand instrument before you ever check with an apex locator or x ray. In the art of endodontics, hand instruments are like fine paintbrushes. Of course, the problem is, you can’t seal your basement walls with fine paintbrushes.
Remember, sealing the apical 1/3 of the canal is pretty much the purpose of doing a root canal at all. What can make this easier? Make the hole wide at the top. Or to use dental speak, open up the coronal and middle 2/3 of the canal so that you have better access to the apical 1/3. So now we’re doing rotary endotontics using a crown down technique. There are two basic principles for rotary instrumentation: vairable taper and constant taper. The best way to think of it is the finished canal shape: variable taper=whirlpool, and constant taper=cone.
Whirlpools: variable taper, variable shape
In residency I used a variable taper GT file system from Tulsa dental. A series would have same size file tips, decreasing in taper as you went from the crown down. In theory, this is the best way to irrigate and seal the apex, because your finished canal is shaped like the inside of a whirlpool. This system also promises disengagement of instruments in series. If your first instrument was a .10 taper, then, when taking the next, .08 taper file deeper, it should not bind coronally, and so forth. Yes, that’s clever. The problem with whirlpools is that they are wide at the top. Sealing these canals is also very technique sensitive. The GT system, as well as many of these early rotary systems are made to work with thermoplastic or carrier-based obturation. These methods are both very technique sensitive, and can often lead to strippnig or voids in the material, in addition to the wide access openings at the canals. Not only that, but heated gutta percha shrinks when it cools. Still, this system can work in the hands of some dentists, and if you’re doing it, and your x rays look good, no problem. Just consider the post core and crown to come. Watch for coronal fracture down the road. Better yet, consider, not the “too small” or the “too large” options, but to quote the story of the three bears, we’re looking for the technique that is “just right.”
Cones: constant taper, constant shape
I now prefer the constant tapered files of the Brassler Endosequence system, and I used this system in school, where lots of faculty and academics supported it. And they were glad that I went out of my way to procure the corresponding Brasseler gutta percha points, from whatever dark alley necessary. (So I had insiders protecting my black market…. I know, you’re saying, “oooh, you rebel.”) These points are stiffer and fit nicely at the apex without turning to moosh or bending. They also have corresponding paper points that are also a little tougher than the standard points.
In this system, you choose a constant taper, either .04 or .06, and use decreasing file tip sizes from the crown down. The finished canal should match the shape of the final rotary instrument that made it to the apex. The canal is cone-shaped, with a constant .04 or .06 taper all the way to the apex. It’s a predictable, repeatable shape. So it’s filled with a matching single cone of gutta percha. When you compare the x rays from the two systems, the cone-shaped canals leave a lot more tooth structure at the orifice than the whirlpool-shaped ones. Brasseler also created a file with 50% less engagement by using alternating contact points along the length of the files. This is their answer to the great disengagement that comes with variable taper. For most cases, .04 tapered instruments work great. .06 taper is used mostly with large maxillary incisors, where the canal is already wide.
Filling these canals has also been simplified. The endosequence system comes with an injectable bioceramic sealer. According to the manufacturer, the sealer itself is adequate for filling the canal system. The gutta percha is just there to hold the space. Once the sealer has been expressed into the canal and is covering the cone of gutta percha,a single cone is slowly placed down the canal to length. This cone fits the canal tightly. As it is carried to length, the sealer is hydraulically expressed into the apical foramen, and any lateral or accessory canals along the way. Here, you can see two fins of sealer faintly coming from the mesial canals.
To me, this is a streamlined system for sealing a canal, and it has less room for error. The single cone of gutta percha is dimensionally stable and does not shrink, because it was never heated. Here’s a good article about the system and properties of this new BC Sealer.
Stay with me here. Here’s how to use the endosequence system.