Ok. You've made the decision to move to Rotary Ni-Ti instrumentation. Now what? Where do you start?
For those of us who were trained at the University of Manitoba and are used to using hand instrumentation with a "Step Back" filing technique, the move to Rotary Ni-Ti is a daunting yet attractive alternative. If you believe the manufacturers claims, there is a temptation to think that these instruments will solve all the problems associated with ledging, tight canals, difficult anatomy and challenging cases. When used properly, they can give you some very nice results. However, when used incorrectly, they can cause real frustration for you…. file breakage, blocked canals and treatment failures.
1. Torque Control Motors- Which Motor should I buy?
Engine driven Ni-Ti instruments are very flexible, strong and sharp but it is also true that when they are used improperly they break with virtually no warning. Most of us are familiar with the "feeling" that you get when you have stressed a hand file to its limit as it starts to unwind or bend. Rotary Ni-Ti files do NOT give you this kind of feedback. When using Ni-Ti rotary file systems, you need to have consistent torque and speed. That is one of the reasons that an electric motor (preferably with Torque Control) is essential for to those who are inexperienced with rotary Ni-Ti. This kind of control is not obtainable when using a compressed air driven engine. Therefore, air driven, gear reduction handpieces should not be considered.
I am currently using the Aseptico DTC (Digital Torque Control). The ATR Teknika and the Kerr/Sybron Quantec ETM are variations. These torque control engines have a "Safety Feature" that reverses the file should it encounter torque levels in excess of recommended value. Think of this as "training wheels". In that way, you get optimal efficiency of the file while minimizing potential for breakage. Another advantage with these units is that they are programmable. That means that they have "one touch buttons" with preset torque and speed values that are provided by file manufacturers (and can be modified by you, should you desire.). (Remember! If you buy your motor from one manufacturer, it is unlikely that they will supply you with the values for a competitor's files!!) The only drawback is cost. These motor systems are very expensive, so choose carefully. Cost ranges from : $ 1400- 1900 CDN dollars ($900-1200 USD) NOT including contra-angles which add a further $700 CDN ( $440 USD) to the purchase cost.
Installation Tip #1: Should you wish to move the motor from room to room, it is a good idea to get a control unit with a power cord that can be detached from the back of the box (rather than one that is attached permanently.) Buy a second power cord. To change the unit to a different room, merely unplug the control unit from the power cord in room 1 and reattach it to the power cord in room 2. It saves your assistant from reaching inside your dental cabinetry to find the outlet when changing rooms .Installation
Installation Tip #2: Most systems show the handpieces lying horizontally on the bracket table or counter top. This takes up a LOT of unnecessary space. Contact the manufacturer to see if they have a handpiece holder that fits the bar that holds your other handpieces. (Sometimes they are not listed in catalogues - Aseptico!) In that way it sits vertically like a regular handpiece, saves space, prevents tangled cords and allows normal access for file changes by your assistant.
2. Which File System should I buy?
There are 4 main file manufacturers: Tulsa Dental (Dentsply) - GT Profiles, and ProTapers, Kerr/Analytic - Quantec and K3, Brasseler - RaCE files, and LightSpeed. There are several other smaller Ni-Ti manufacturers with variations in file design. I have used several types and I suggest that new users choose the Tulsa GT ProFile because of the quality reputation of the product AND more importantly, the attention of my local Tulsa representative, John Hargreaves. John is knowledgeable and responsive to your needs. He visits Winnipeg monthly and is always available for assistance, whether it is with orders or technique related issues. Get to know him. He is a valuable resource. (I am NOT being compensated for this recommendation!) The ProFile system is easy to understand and intuitive for your staff. Files have three characteristics: Length, Tip Diameter and Taper. Available lengths are: 16, 21, 25 and 31 mm. Tip diameters are available in size .20, .25, .30, .35 and .40 mm. Tapers are .10, .08, .06 and .04. For example- a 25 mm, .20, .04 file has a length of 25 mm a tip diameter of .20 mm and a taper of .04. Tapers are easily identified by their color-coded stripe. (Yellow= .20 tip size, Blue =.30 tip etc.)
3. How much of a selection do I need?
One of the most difficult tasks for clinicians new to Rotary Ni-Ti is deciding which length and sizes to purchase because these files are NOT cheap. ($50-60 CDN per pack of 6). In order to equip yourself with a reasonable selection of all lengths, you will need to purchase at least 30-50 packages of files at the start. Even with this amount, you may end up with only 6 files of each size, which will not last long. The inventor of the system, Dr. Steve Buchanan was recently quoted as saying that he insists that you NOT use his files more than once because of risk of breakage. Because of this many clinicians are shocked at the costs that are incurred in keeping a fully stocked selection. When considering Ni-Ti files, it does not pay to be "cheap". Do NOT be tempted to use the same file repeatedly in different teeth- they WILL break eventually. You may be lucky for a few cases but the odds are not with you. If you do not wish to accept this increase in cost/case for the increase in speed and ease of treatment- then I strongly suggest you return to hand instrumentation and forget using Ni-Ti Rotary instruments.
4. TECHNIQUE - Pure Crown Down or Working Length First?
It is first necessary to decide how you wish to use these instruments. I have been a firm believer in establishing working length (WL) with small hand files before attempting to use rotary files. This may not agree with proponents of the pure "Crown-Down" philosophy but I believe that getting a working length first is more in keeping with the training that most of us (in Manitoba) have received and offers less chance for Ni-Ti instrument separation during the initial learning curve.
Step 1. Select a case of reasonable length and anatomy. Experienced clinicians should start on a canal of less than 21 mm with little, if any curve. Avoid canals that may have sharp bends at the apex (maxillary laterals, certain maxillary premolars and distal canals of lower molars.) Look at the film closely and try to establish the approximate canal length and direction of the final canal curvature. Broach as much of the canal contents as you can before starting. Always use copious irrigation with NaOCL. Never use any instrument (hand or Ni-Ti Rotary) in a dry canal.
Step 2. Establish proper access and Glide path with no obstructions at the orifice level. Select a #8 or #10 hand file. Place a small rounded bend at the very tip. Use this as your "antenna". Slide it down the canal space slipping and sliding as you proceed apically. Alternate NaOCL with applications of RC Prep. (Please note: RC Prep is dangerous stuff! It is NOT to be used in the "canal finding stages" with larger than a #10 hand file. Using RC Prep with a stiffer #15 file can cause perforation of the canal if the file is used aggressively at the apex! BE Careful. ) If you appear to be close to the apex (as measured in your pre-op film) take a reading with your Electronic Apex Locator. Confirm you are at the apex. If you are short…don't panic and don't force the instrument. Remove it, re-bend it with a sharper bend and then re-insert it, taking care to very slightly rotate it to "find your way down". You may have to discard several files before you reach the apex.
Step 3. If at this point you are still short of the working length, take a .10 taper .20 ProFile GT Ni-Ti rotary and use it in the canal orifice. Make sure to wipe the flutes immediately after insertion. With a size .10 taper instrument, the actual number of cutting flutes on the working part of the 21 mm file is minimal. The dentin mud will accumulate rapidly and it is this dentin mud that will prevent the file from reaming properly. Because of this clogging, there will be an increase in resistance to advancement of the instrument. Before gaining experience, there is a tendency to push on the file at this point to make it move deeper. This is an error and is one of the biggest causes of fracture of "new" instruments. Instead, remove the file, re-clean the flutes and re-irrigate. Reinsert the clean Ni-Ti file passively and remove it when the file stops advancing. Don't force it. Now try the hand file again. By enlarging the orifice in this manner, we straighten the coronal portion of the canal, give the hand file a better angle of attack and have fewer coronal restrictions. In a sense, this can be considered a "Modified Crown-Down" since we are working the coronal or body portion of the canal before achieving working length.
Step 4. Having removed coronal obstructions, we now establish working length with a #15 file at the apex and confirm it both electronically and via film. At this point, re-irrigate and re-establish patency. It may occasionally be necessary to use a smaller hand file (#8 or 10) to "clear" the apex if the #15 file suddenly does not seem to go to length. Once you have reliable reproducible patency with a #15 hand file, you can move to the Ni-Ti Rotaries.
Step 5. In most cases a size #20 or #25 instrument tip will be sufficient to allow you to and achieve proper shape. Again, size .10, .08. 06 and .04 tapered instruments are used in sequence until they don't advance. Proper irrigation and flute maintenance are critical. Frequent recapitulations with a small hand file will ensure apical patency. For those who prefer more flared canals, larger tapered accessory Ni-Tis can be used in the coronal part. I prefer to use 3,4 and 5 Gates Glidden drills because I am familiar with their use. This gives me slightly greater taper at the coronal aspect, something I prefer when using the classic Warm Gutta Percha fill technique. This also allows me to get a set of Schilder pluggers slightly deeper than the normal shape created by the GT Profile system. Buchanan's own Ni-Ti pluggers correspond more closely to the classic GT shape. It is a personal preference. Dry the canals.
Step 6. A Gutta Percha cone fit is accomplished using the corresponding specially tapered Gutta Percha. (I use Kerr AutoFit.) Cones are cut to length. Although gauges are available to cut it to exact foramen size, I usually eyeball it since curvature must also be taken into consideration. There has been much discussion on the ROOTS internet forum on how much sealer to use. Many clinicians are moving toward very small amounts of sealer, only on the very tip of the cone. They believe that filling the canal with the maximum of gutta percha and the minimum sealer gives the best seal. Use a warm GP technique of your choice but do "stay warm".
Rotary Ni-Ti Instrumentation is less fatiguing and faster than conventional hand filing in most cases. However, the clinician must use them in a disciplined manner, always aware of the limitations of the instruments and recognizing that purchase cost of these instruments cannot be compared to conventional files.