by Richard Mounce, DDS
For more on this topic, go to www.dentaleconomics.com and search using the following key words: root canal, obturation, RNT files, Twisted File, Dr. Richard Mounce, Endo File.
I recently received this e-mail from a reader asking questions about an article I had written on the new rotary nickel titanium (RNT) Twisted Files (SybronEndo, Orange, Calif.).
“Good evening. I finished reading your article in the May 2008 DE and have some questions regarding the Twisted File (TF) protocol. I currently use the SybronEndo K3 files with the System B unit, and my file sequence goes from a .02 taper size 25-40, followed by a .04 taper size 30-40. I place a K3 size 40 gutta percha point to WL and use the System B to obturate. I achieve excellent results with this protocol, although it does take a bit of time when filing four to five canals with nine different K3 files for each canal. After reading, I have some questions:1 “With the TF, are the various canals only being filed with one or two files instead of an entire size range, such as 15-40, of a particular taper size, like I am currently using? If so, how is it possible to achieve a proper root canal system shape as well as endodontic irrigation with so few files compared with, say, the protocol I use?”
Larger apical tapers can be achieved using TF (which is manufactured by twisting nickel titanium in the rhombohedral crystalline phase configuration) from the orifice than can be achieved using RNT files that are manufactured by grinding.
For example, a .08 taper TF can be used as the master apical taper in most molar roots of average or moderate difficulty, and in many roots can be the only file required to reach TWL. TF also requires fewer insertions (three to four) than many ground RNT files to reach the apex using this single file if used appropriately.2 “It seems like a .12 or .10 taper TF is huge compared to a K3 file. If so, how are you able to place the entire file in the canal when it is so wide? The same goes for the recommended .10 or .08 taper TF for medium canals, as well as the .08 or .06 taper TF for lower anterior teeth.”
The .12 TF is used primarily as an orifice opener and is rarely taken to the true working length as a master apical file. Many large canals — the palatal root of an upper molar, for example — will allow a .10 taper to be created to the apex. Creating such tapers is a function of TF's cutting ability, flexibility, and ease of canal tracking and appropriate tactile use.
After a glide path has been made with hand K files first, TF is inserted passively to resistance and withdrawn in a single continuous and controlled motion.3 “Is the taper size for the TF the same as for the K3 files? If not, how are they different?”
Both systems have five tapers that are identical: .12, .10, .08, .06, and .04. K3 has a wide variety of tip sizes, and at this time TF has only one tip size, No. 25. Additional tip sizes will be introduced in the coming months.4 “Are there different (new) gutta percha points for the TF system vs. the K3 gutta percha points I currently use?”
Matching K3 and TF gutta percha points are available for each RNT system.5 “Do you still (need to) use Gates Glidden drills to open the canal orifice with the TF system, like I do with the K3 files?”
It could be persuasively argued that Gates Glidden drills are not needed for the K3, but its discussion is beyond the scope of this column. TF makes Gates Glidden drills obsolete. Due to its attributes, TF acts as both an orifice opener as well as the canal-shaping file.6 “What canal irrigation system do you use to achieve complete canal debridement and dryness prior to final obturation?”
I irrigate vital cases with 5.25% sodium hypochlorite. Nonvital and re-treatment cases are irrigated with 2% chlorhexidine. The smear layer is removed with SmearClear* to allow bonding of the obturation with RealSeal*, either in the form of RealSeal master cones and SystemB, or via the RealSeal One Bonded Obturators*, a warm obturator-based system for bonding obturation. All final irrigations are ultrasonically activated.7 “How do you determine how many TFs to use with each canal?”
If the canal will allow the passive and successive insertion of a TF, it is reinserted. If the TF does not want to advance apically and do so without undue pressure, the next smaller TF is used. This sequence is inherently crown down.
I welcome your feedback.
*SybronEndo, Orange, Calif.
Dr. Mounce offers intensive, customized, endodontic single-day training programs in his office for groups of one to two doctors. For information, contact Dennis at (360) 891-9111 or write [email protected]. Dr. Mounce lectures globally and is widely published. He is in private practice in endodontics in Vancouver, Wash.