Clinicians who attended dental school in the 60s, 70s and 80s were most often trained to perform endodontic treatment with Push-Pull, Step Back type preparations. Since the early 1970s in Manitoba, we had the advantage of being taught this technique for use with Warm Gutta Percha Obturation. This combination worked particularly well with canals that were properly cleaned and shaped. When treatment was performed as taught, the success rates were (and continue to be) very good. However, many clinicians become frustrated with the tedium of shaping canals, the predisposition for ledging in curved canals and their inability to maintain patency…a requirement for proper treatment. (Remember, a vital canal cannot be "calcified" at the apex - that is a loss of patency -> operator error!!)
One of the ways that I avoided this problem was by maintaining strict adherence to the method I was taught at Boston U. It relied on the use of reamers in rotary/withdrawal motion. (Some of you may remember that Donald Yu mentioned the "Envelope of Motion" of the reamer and my graduate research during the Alpha Omega Memorial lecture some years ago.) After almost 20 years of using this method, I became pretty adept at very rapidly shaping canals by opening the body of the canal first and then performing final apical shaping at the end. Reamers are quick!
The incorporation of Ni-Ti alloys into Rotary Endo instrumentation resulted in a revolution in endodontics but one that must be understood before you make your move. Although my initial trials with Tulsa ProFile GTs were promising I must admit that I was still getting unacceptable rates of instrument separation, even when using Tulsa's torque control motor. The most frustrating aspect was that these separations occurred without any warning, even with new GT instruments. And it wasn't just the tip of the instrument that was breaking; frequently it was 5 or 6 mms of file that broke off. I believe the problem of instrument breakage was due to what I call "Taper Lock". This occurs when the constant taper of the instrument corresponds to the taper of the shaped canal and too much of the instrument comes in contact with the canal wall. The file becomes "locked" in dentin for a split second and if there is sufficient curvature the file breaks. I was also disappointed with the number of instruments required to treat a case and the need for a vast inventory of these expensive files. My staff were constantly confused about which instrument , taper and tip size I needed next and how many instruments needed to be set up. What we needed was a system that was more efficient, more resistant to breakage, and that required fewer instruments to complete a case.
Dr. Cliff Ruddle and others found this better way when they designed the ProTaper system. Since my introduction to this system, I have drastically reduced instrument breakage. The cases shape more easily and I am more confident in using them. I no longer have that feeling of uncertainty when picking up a rotary handpiece, wondering if I will break a file. Not surprisingly as my confidence in the instrument system increased so did the ease of treatment and speed.
What has made the difference and what is so special about these files? The key was in varying the taper of the file. Firstly, there was a philosophical difference in designing these files. What is unique about the ProTaper series is that the actual taper of the instruments varies within the individual instrument. i.e./ A file may have one taper higher up toward the shank and be "non-cutting" at the tip. Other instruments are used for apical preparation by having the apical portion as the cutting part of the instrument while engaging the body of the canal less. The result is virtually no chance for Taper Lock along the entire length of the instrument during use and dramatically reduced chances of breakage. The shapes are also much nicer and the increased bodywork allows for better access to the apex for better "deep shape". Deeply shaped canals are cleaner and easier to fill.
The first file in the series is the SX.
It is 19 mm long and serves as a combination GG bur/orifice opener/body shaper. Unlike any other Ni-Ti design, this file is meant to be used in a lateral brush motion. You can actually lean on the surface you want to straighten (like the MB2 lip I described in the Jan. and Feb. 2003 Endo Faxes) with this file. It is very sharp and very aggressive, very much like a large reamer. This file opens the body while at the same time not cutting at the apical portion of the file. Ruddle even suggests that you can use these to open the orifice (even before achieving working length!) Dentin shavings are visible at the coronal aspect of the file but not apically. That is why they never break if they are used correctly!
A second set of files; S1 (purple) and S2 (white) are used to shape the body. Again, because of the differing tapers, the apical parts of the file are not active! When you use these you see that the shavings generated are at the middle and coronal parts of the file, not at the end. This shaping provides space for the third set of instruments.
The Finishing Files F1, F2, and F3.The Finishing files (F1 (yellow)= size 20 at apex, F2 (red)=25, F3 (blue)=30) work at the apex and are used ONLY BRIEFLY! Because they are end cutting, you do not want to leave them at the apex for more than a second or two. You use them to "fine tune" the middle and apical part of the canal. The shavings appear apically on the file, which is why you don't want to leave them in the canal too long. (Don't tear the apex!) ProTaper Files are available in 21 and 25 mm lengths. With proper technique, torque control and discipline, it is possible to shape these canals very rapidly, maintaining curvatures, getting proper deep shape with no transportation. A case can often be completed with only 3 or 4 files. Once this is done, placing a corresponding .06 taper gutta percha cone becomes a breeze and obturation is simple. No more struggling with cones to try to get them to place in an undershaped canal.
It is my belief that no matter which files you use; you still need to be able to obtain a consistent "Glidepath". You must be able to the reach the apical foramen consistently with a #15 Stainless Steel hand file before moving to these Ni-Ti rotary instruments. Can you occasionally "work your way crown down" with them before getting that #15 file to the apex? Yes, in large canals this can be done, but it is risky for the kind of cases that I see. (80% molars, most with small, tight or curved canals.) My own method still uses hand files to achieve patency and working length before using rotaries.
One last word about file re-use. We all know that Manitoba dentists are famous for their ability to keep their overheads low. (Although we have some of the lowest dental fees in the country, we still rank as some of the best earners in Canada.<-FACT) At $77.00 CDN for a pack of 6 ProTaper files (!), there is a tendency to want to use these files many times to "get our money's worth". This is a mistake and WILL contribute to breakage. Rather than risk breakage it is better to raise your Endo fee to cover the cost of a NEW set of files …at least for each molar that is done with them. I will not use Protapers more than twice, and frequently I will toss them after only one use in a difficult molar. It just isn't worth the risk of breakage. Don't be cheap with them and they will work for you! Call me or your Tulsa Dental rep if you need further information.
Mark your Calendars now -
ROOTS Summit III June 18-22, 2003 in Anaheim California
$350 US registration fee for 4 full days of quality CE! Its at the Disneyland Hotel.
Bring your Family!Many World Class Endo speakers picking up where we left off last year!
Cliff Ruddle (Retreatment) John McSpadden ( Instrumentation), Martin Trope ( Obturation and Success), John West ( Creating "The Look"), Jim Roane ( Balanced Force Technique), Steve Senia (Lightspeed) John Stropko (The "No Cone" System S "Squirt" technique), Fred Barnett (Treatment Resistant AP), Arnaldo Castellucci (Working length and Endo Surgery), Barry Musikant ( The Safe Sider Instrument) Drs. Koch and Brave (RealWorld Endo) and much more. "Lunch and Learn" every day. Exhibits, Parties and dinners ! It's a non stop Endo University !
Check out www.rxroots.com or call me for info. Don't miss it !