This reading would have saved me a lot of headaches after graduating... File breakage should be infrequent....like 1 or 2 files per 100 teeth. I've broken files. I've had a few bad ones. But it is a very rare event. Rarely do files break completely without warning. The trouble is we sometimes don't know what the warning signs are....or the dangerous ways that we use them are not recognized as being dangerous....and essentially we're getting lucky a lot. You should probably be breaking more files than you do but you're just lucky that they don't break. You don't know it though. As we build our understanding of what we're doing we get better. Take crown impressions. As you practice longer and longer you get better and better at taking them and you understand what the problems are that give you poor results. Same with filing. The bad thing is that most general dentists do more crowns than root canals... Any file will break when it's cutting too much. It's not the curves. We've seen plenty of guys post cases over the years with crazy curves that were instrumented with rotary NiTi files. If it was the curves that broke them they'd be loose in the canal after they broke. The brilliance Steve Buchanan introduced with the original Greater Taper concept was that if you aren't cutting with to much of the file at once you won't get into trouble. It's like sawing a board with a hand saw. You have to periodically change the angle of the saw in relation to the wood to keep the drag down. So you change the angle and immediately start cutting less of a bite. You have to think of your instrumentation sequence the same way. The coronal canal needs to be shaped. Gates glidden #2 and #3 are great for this and they are relatively cheap. That gets the coronal 2-3mm of the canal to a size 90ish and the next 2-3mm to a 70ish. How hard is it once you're at your length with a 15 to take a 20 there? then a 25? That's easy. Then grab a 30 and take it with a little balanced forces to wherever it wants to go without putting any muscle into it......repeat that with a 40. NaOCl rinse throughout all this and every 3rd file take a 10 file to patency. This seems like a lot to do if you're a dental student and are working in the lab out of your "cookbook" instructions.....but if you're already taking a 15 to length...I'm talking about adding about 2 minutes of hand filing onto the procedure at this point. If you do this you will never break a rotary file. You just won't. At this point.....you've not used any rotary files but you're already at a 25 at WL and have about a 4-6 taper in the apical 4mm and a 5-7 taper the rest of the way to the orifice. At this point you could jump right to the F1 which is a 20-07....the tip won't even engage but the file will basically smooth out the remainder of the canal. Now jump to a landed file at 25-06 or 30-06 and that should go to length with little effort. In most smaller canals you are essentially done. In a larger canal you might want to take a 30-08 GT or GTX to deepen the shape. These shapes are easy to create and can be irrigated well. So that's what? 2 rotary files? Chuck them. Studies show that you can't predictably clean them.....and NiTi doesn't hold an edge as well as steel....and a duller file means more drag. It's only 2 files. That 30-08, if you didn't have to push on it, could probably be re-used another time. There are many other ways to do this. Think about cavities...if a patient wanted.....they could probably take measures to ensure they would never have another cavity in their life.....it could conceivably be done. It's a motivation factor.