It appears that a lot of people are fascinated with what the vehicle is made of and care very little whether it's a Porsche or a coaster wagon.
Nickel-Titanium alloy has some interesting properties. It is indeed very flexible. It is also soft.
To fully understand the NiTi you have to ask, what techniques is it good for and under what circumstances.
To do vertical condensation of warm gutta percha it is essential that you be able to get your pluggers close to the apex because heat only travels a short distance through gutta percha.
It is also essential that the canal be round.
If the canal is ovoid and the plugger is round, pressure is dissipated laterally instead of longitudinally and if the diameter of the plugger is greater than the minor diameter of the canal, potential root splitting pressure is exerted on the walls of the canal.
Therefore if you are going to do warm gutta percha properly, you have to have a round canal near the apex even if that is around a curve.
To do this you must either carefully precurve files or use a very flexible instrument in a rotating handpiece.
My argument against NiTi rotating files goes like this:
If the handpiece rotates 300 rpm that is 5 rotations per second.
How many times can you rotate a NiTi file after it gets stuck before it twists off. Perhaps two. Maybe three. (Studies show 540 degrees)
That gives you 2/5ths to 3/5ths of a second to notice the sticking and stop the handpiece before it breaks the file.
In order to enlarge a canal by rotary reaming, which is what rotary files do, it is necessary for the entire surface of the file to be in contact with dentin. The more surface area in contact the more friction and thus the more torsion placed on the instrument.
To a great extent this can be mitigated by lubrication and more importantly by technique. Lubrication can only be applied until the surface of the file contacts the surface of dentin but as soon as cutting occurs, lubrication can no longer reach the interface.
That leaves us with technique.
The idea behind the technique is that downward pressure increases friction and thus torque.
The operator...that's you... have to learn not to apply enough pressure to create enough torque to break the file.
How much that is is undefinable.
You just have to develop the technique.
Circumferential filing eliminates both of these hazards.
The lubrication and irrigation can reach the interface because the file is only in contact at one locus of points along the long axis.
This also minimizes friction and not just incidentally, allows the debris to escape with the irrigation fluid.
It also means that the canal can be scrubbed clean without demanding that it be made round.
Properly done(and it is easy to do it properly) circumferential filing does not cause breakage since the file rarely or never gets bound.
Now you can learn this technique by taking the course in your own office via the video conferencing route.
If you have a Macintosh computer, video conferencing is built in. All you need to add is an iSight camera which plugs into a USB port and uses iChat software, which is part of system 10. Simply arrange a time and gather your group in front of the computer.
Groups of one or more can be accommodated.