Paul Rodgers of Bad Company fame sang about his “Rock and Roll Fantasy.” The song was a hit. Most of us won’t ever be rock stars. But I suspect that many of us harbor a real satisfaction when we achieve an excellent endodontic result that might make us feel like a rock star, even if only for a moment! Creating excellent endodontic results to create a feeling of pride and satisfaction is now easier than ever with recent innovations in endodontic instrumentation. Historically, hand filing has been a time-honored method of root canal preparation (often in conjunction with Gates Glidden [GG] drills). Hand filing requires that the shape imparted by each K file (or reamer) and the various GG drills are blended into the desired tapered funnel that represents the ideal preparation for an endodontic filling. This blending with hand files and GG drills can certainly be a challenge. The limitations of hand filing, in conjunction with GG drills, are myriad (canal transportation, repetitive and multiple file use, hand fatigue, time required, risk of mid-root perforation on the thin furcal side of roots - especially the mesial roots of lower molar teeth) among other potential problems. In addition, with hand files, preparations - especially apically - tend to be small due to the inherent challenges of instrumenting the apical third to a size that facilitates irrigation and obturation. Large K files and reamers, particularly those above a size 20-25, are inherently stiff and want to straighten out. This causes an “elbow” or ledge on the wall opposite of the canal curvature. Many of these problems are overcome with rotary nickel titanium (RNT) files.
The above notwithstanding, it could be said that a master can create an excellent endodontic result with any combination of instruments because they understand fully the biologic requirements of the procedure. So why would someone opt to use hand files when RNT instruments offer - when used safely and efficiently - a vastly more efficient option?
To be fair, RNT files - by comparison - also can separate and create transportation, but their efficient and effective use is akin to flying across an ocean in first class as compared to going by boat. Both will get you to the destination, but with immensely different efficiency. The vast majority of clinicians who use rotary files would never switch back to hand filing, much like those who routinely use a surgical microscope would not change to loupes.
It is somewhat misleading to discuss all RNT files collectively since different systems have significantly different attributes and limitations. As such, in practical terms, there is great value in studying and practicing with the particular file as much as possible before it is used. Also, use the file in extracted teeth, and - if possible - watch your local endodontist use his or her chosen system of RNT instrumentation. Read beyond the product literature and survey the relevant dental literature on any given file before using it clinically. There is no substitute for this type of direct observation. Better yet, take the local hands-on course offered by the chosen manufacturer for the given file. Having the instructor hold your hand to determine the correct amount of pressure to be placed on the given file during insertion can go a long way toward efficient RNT use.
What complicates the picture somewhat in RNT use is the often conflicting claims by manufacturers regarding suitability of use and attributes of a particular file. General strategies for the use of any given RNT file (across brands) are similar, but recommended strategies may not be universal. For example, the LightSpeed file (LightSpeed Technologies, San Antonio, Texas) is recommended with a “pecking” motion. Such a motion for other files, such as the K3, would be inappropriate.
As mentioned in previous columns, I am a strong advocate of the K3 system (SybronEndo, Orange, Calif.) due to its robust cutting efficiency and fracture resistance. Aside from these features, I like the K3 because it comes in a variety of tapers and tip sizes. This provides a system that is universally applicable to almost any canal anatomy, if used appropriately. I like the .02 tapered K3 files to blend my hand-created glide path with the subsequent K3 files, which will be used to shape the canal. The K3 has proven an invaluable part of my armamentarium, and has helped facilitate - in part - the satisfaction that comes from earning a great clinical result for the patient. Rock steady!
I welcome your questions and feedback.
Dr. Richard Mounce is in private endodontic practice in Portland, Ore. Dr. Mounce is the author of a comprehensive DVD on cleansing, shaping, and packing the root canal system for the general practitioner. The material is also available as audio CDs and as a Web cast pay-per-view. He lectures worldwide and is a widely published author. For more information, contact Dr. Mounce via e-mail at comfort@MounceEndo.com. Visit his Web site at www.MounceEndo.com.