Qualitative change
Since the advent of the the new Endo Contra-Angle for root canal preparation we have found that it is more than a quantitative change. It is qualitative as well. The best example I can give is the difference in dentistry before and after belt driven handpieces were replaced with air turbines.
After having opened the access and flushed the pulp chamber with water, we now use a size 25 or 30 Fine Cut File[First File] in the Fine-Cut Endo Contra-Angle and inserting just the tip, move in a circuferential manner. As we do so that the orifice opens up allowing the file to enter further. We proceed with this technique(called Spiraling Down) which combines orifice opening and crown down preparation and which is called, you guessed it "the Crown-Down-Orifice-Opening Technique". In many cases, the tip of the file ends up more than half way to the apex and in some cases within a few millimeters.
All this while using a constant supply of water. Water enters the canal by capillary action. There is no need to aim or direct the water. Simply flood the access cavity.
Each stroke of the file(1mm in and out) displaces the water from the tip of the file coronally and each up stroke capillaries more water to the end of the file. This creates a circulating pattern that completely flushes the canal every two seconds.
At a certain point, the file will get stuck. (Not to worry, this doesn't hurt anything.) This indicates one of two things. Either the canal is too small for the file or the canal is too curved for the file.
Then it is a simple matter to use a smaller file to do the rest of the canal or to pre-curve the file or both.
Getting a Fine-Cut SPeed file stuck is of no consequence since these files are the same design as the Fine-Cut Hand Files and have been designed to pull themselves free without danger of breakage. In fact they are used for probing calcified canals.
At this point probe and measure. Once you have probed to the apex to a size 15, the next step is to use a #20[Second File], inserting it close to the apex and as you move circumferentially, move the file out of the canal(spiraling out). Repeat this process six or seven times.
At this point you have a canal that is smooth, patent, clean and tapered.
What's left to do depends on how you intend to fill it. With the pressure filling technique with the new Multi-Mode or Cartridge Syringe you can fill it immediately. Simply blot dry and fill.
No need for post-preparation irrigation
There is no need for irrigation AFTER you prep because you have been doing irrigation all the while. After filing with the Fine-Cut system the canal is already as clean as you can get it by irrigating.
If you choose to irrigate with sodium hypochlorite solution, you can do that after the final stages of filing, following with a sterile water rinse. In other words, there is no need to use a syringe as irrigating while filing is much more effective. In fact if the canal is smaller than size 35, there are no needles small enough to get into that canal and if you were to push it in, there would be no back flow and the fluid would go out the apex.
If you still use the Passive Filling Technique I taught many of you in the last 25 years, there are a few more steps. Mainly preparing a seat for the needle(30 gauge is 0.29mm) using a size 35 hand file or a series of LightSpeed NiTi files(my favorite is a size 32.5) or a size 35 in the new Endo Contra-Angle to the 1mm point.
If you are still packing gutta percha, there are even more steps. Why anyone would want to spend the extra time and enlarge a canal beyond clean, smooth and patent is beyond me, when we have methods today that enable a fill with an ADA certified cement under very good control.
In the April issue of the Journal of Endodontics research has shown that indeed the BEST method of backfilling is to inject cement.
But that requires a more complete explanation that I have room for here.