Rotation vs. Reciprocation: Which is a Better Instrument Motion?

You're listening to The Dr. Phil Klein Dental Podcast from Viva Learning.com. Welcome to the show. I'm Dr. Phil Klein. Today we'll be discussing instrument motion and the difference between rotation versus reciprocation. Our guest is Dr. Ali Nasseh, a clinical instructor and lecturer at Harvard School of Dental Medicine, specifically in the endodontic program. He is the current director of the endodontic microsurgery course at Harvard and also runs a private practice limited to endo in downtown Boston. Dr. Nasseh is also the CEO and president of Real World Endo, an endodontic education, innovation, and medical device company. Dr. Nasseh, it's a pleasure to have you back on the show. Thanks for having me, Phil. This is the fourth part of the endodontic series. We covered quite a bit, and you can look at the previous podcasts by Dr. Nasseh. So before we talk about rotation versus reciprocation, can you tell us some general concepts about instrument motion inside the canal? We kind of realized early on in the field of endodontics that when you're trying to clean or remove debris, tissue, and microbes in an open-ended tube, where on the one end you have the potential of pushing stuff out and cause problems, and on the other end your goal is to get everything out through only one end, that is the... the proximal end that you end up having a number of challenges involved here because first and foremost in a closed system as you're cutting you're generating debris the debris has nowhere to go so that debris will get clogged or get pushed laterally and all of these things especially when it comes to what we discovered to be probably the most efficient method of cutting this tooth structure would be to rotate some type of a blade inside the tooth then the blade would have to have some spaces, and it's called the chip space. And then it gets very quickly, it gets clogged up with the debris that's been cut. And as soon as that space gets caught, that gets filled up and clogged, then it generates additional force into the axis of the instrument. So from an engineering point of view, the chip space of the file is a super critical part of the file, and it has limited... uh volume and as soon as it gets full then it starts to torque the file so when i was a resident back in you know early 90s when nighttime files were invented and was lucky because i was in the first class of the first year where nitile files were introduced and our program here at harvard was uh was my program if you had the insight of understanding or the foresight if you will of knowing how important these things are so we were the first program to to incorporate nitile files into our uh curriculum so right from the get-go i started going on the nitile files and from 93 all the way now to to now all the 27 000 cases that i've done been an evolution of seeing these nighttime files evolve over time with different designs and motions. There was no kind of user's manual early on. So we kind of had to do all of this learning on using these rotational motion in these canals all on our own. So it was a trial and error thing. And the many things that I learned over this time was the reality that the engineering component part of this whole thing and the chip space and the debris management are the critical parts of maximizing and running that line between having maximum efficiency while being safe. because that's the keys if you end up getting too much debris clog in there all of a sudden your file will snap off because it's over torque yeah so that's really a good background on the understanding of chip space and where the torque is created and how the file functions from the engineering standpoint now from the standpoint of rotation versus reciprocation does a dentist use a combination of both of those forms of motion yeah that's that's that's a good question here so essentially When we started with the NITI instruments, the first motion that was introduced was rotation. And that's because rotation is the most efficient instrumentation motion from a kinematic point of view, which is like an engineering term for saying instrument motion, essentially, is rotation can cut the most, can cut the most efficiently and the best. But the problem is that because rotation cuts so efficiently, as I mentioned, the chip space can get clogged very quickly. It becomes a question of having that proper tactile feedback and having hands that are really kind of connected to the handpiece and can feel the cutting so that you can previously feel, you probably remember this was done by just feeling the file when you were hand filing. Now with using instruments, now that's extended to the feel of the handpiece. So when we end up going to rotation, it ended up being a big problem and a disaster. Many people were instrument breaking files because they were staying in the canal. They were using their hand pieces like a Black & Decker drill, right? So that was an issue over time. Slowly but surely, you know, manufacturers started to kind of put in different type of features, technological features and computer algorithms into the hand pieces that made them kind of... um torque response that the file have different exactly control the torque torque controls and things like that so that the file would just go crazy in there and start cutting and getting over torque and break off then all of a sudden we went from rotation and then rotation with some torque control to you know some of the manufacturers decided that they're gonna well why don't we have this idea that we previously had which was reciprocation which is cutting back and forth back and forth in the same exact degree of uh of um clockwise or counterclockwise rotation, let's increase the direction of motion in one direction more than the other one, so-called asymmetrical reciprocation, so that you end up having a net effect of cutting and releasing, cutting and releasing. And the whole idea here was just to release the debris that's in the chip space as the motion is going on. Unfortunately, the company that basically put this thing together decided that they're going to have the... of motion be in a counterclockwise direction as opposed to clockwise direction where every other rotation instrument was was happening but that reduced the cutting capability of did it not no no no i didn't because no i didn't that because the files were designed to cut in a counterclockwise direction okay okay so all the reason they did that is so that you couldn't use every other manufacturer's files on that same motion there you go so that was essentially done so that you get locked into one patent okay that's what that's when i suggested that i said okay that's going to reduce cutting capability but not if the file is proprietary to that exactly system okay that's where i missed out you're precisely right so they were smart in that sense there was a beautiful business move to be honest is that it allowed the uh you know people to get locked into a given system and a given engine and a given handpiece and so on but over time especially as that pattern started to wear off people had different motions in which ended up people ended up having the same kind of idea combining that torque control with rotation in a manner so that the torque control was much shorter lift so it almost appeared like reciprocation but now in a clockwise direction and that was the adaptive motion as well as the otr motion these were going to come They were kind of reciprocation-like motions, but in a clockwise direction. Now, in a sense, you could say, as you just mentioned, you could have both motions. OTR, for example, which is optimized torque reduction, is exactly that. As soon as it feels that there's a stress point, it goes into reciprocation mode. absolutely you program what is that stress point you know how much how much what amount of torque is uh do you want and in fact you have different settings you go from 0.2 to 0.4 to 0.6 to 0.8 to 1. And I always tell people is that, you know, based on the difficulty level of the tooth and your desire for safety, you can go, it's kind of like having training wheels, you know, at different heights, if you will. It captures you at different levels. If you're doing tooth number 31 and you're doing a very calcified case, you want to make sure that the OTR is set so that it's very sensitive. So if it starts to pick up some stress on the file, it's going to... off and go more into reciprocation is that correct yeah the tighter the canal uh you you can set the otr to be lower and that becomes safer but that essentially is a scale which you have to decide. You have to balance out your needs for safety against your needs for efficiency because the safer you are and the lower the torque setting on the OTR, for example, the more inefficient it is because you're sitting there and this thing is not cutting. It just keeps going back and forth, back and forth, back and forth. So you need to kind of fine tune that to find out what is the right amount. With experience, you will know, but I think for a novice, it would be safer to go on the lower side at the beginning and then slowly up the torque so that you can find. what is that limit that works in your hands. That's what I usually recommend. So when a doctor wants to go purchase one of these systems, what comes with the system? What does a standard package look like as far as the motor, the handpiece? Are they compatible with, if they have a handpiece from a different system, could they use a different motor? Tell us quickly a little bit about that and then any recommendations you might have. Sure. So first and foremost, you need to kind of decide what file system you have, because there are different files cut in different directions, as I mentioned now. So most of the files cut in a clockwise direction. And for that, you can have just regular handpiece from any manufacturer with torque control. If you have OTR, this would be like in Brassler's Endosync handpiece. It allows you to have that. But if you have files that cut in a counterclockwise direction, they require reciprocating handpiece. Now, you can go. with a densely handpiece that has a pure reciprocation motion, which it only reciprocates. The alternative to that would be, again, Baster has also this endosync plus handpiece that allows you to have rotation in a counterclockwise direction with OTR. So that's an interesting option now. All of a sudden, instead of just being limited to having reciprocation, you can have counterclockwise rotation with OTR, which means a combination of rotation and reciprocation. essentially so you end up being able to all of a sudden make your counterclockwise cutting files tremendously more efficient as well by again manipulating that torque setting on your otr so you can cut more or less so again and that's one like you said when you started talking about this um when you were responding to this question you said you have to choose your file system right because that's that's the determining factor obviously in what system that you're going to use as far as That is a determining factor. Currently, though, the Endosync Plus handpiece by Brassler is the only universal handpiece on the market that allows you to use essentially every file that's out there in either rotation or reciprocation motion, which is the OTR equivalent type of situation. That's because it has counterclockwise rotation. Yes. So I kind of wanted to have make sure that this system is an open source system. So it's future proof so that if there are other things in the future, it allows you to have rotation in a clockwise direction, rotation in a counterclockwise direction, OTR in a clockwise direction, OTR in a counterclockwise direction. And you can furthermore change the angles of reciprocation in a cutting and a non-cutting direction to whatever angle is best. So if the next manufacturer comes up with a, you know, more. positive rake angle so you want to reduce the cutting angle direction you can do that so it essentially is kind of future proof in a sense and it's cordless and it can connect it to an apex locator too so you get tons of additional benefits by doing that so you can use yeah tell us real quick about yeah tell us real quick about the apex locator on that system it's incredibly useful i mean i no longer use a hand file to measure my working length i'm using my rotary files to measure the working length and that's uh saves me tremendously from the use of extra hand files while I'm working. And what it does, you essentially connect the Apex Locator that uses the Morita technology, which is the RootCX technology, which is the gold standard for Apex location. There's been tons of studies done on that. It uses that technology connected to the handpiece, and it has a lead that you just connect to the patient, the lip clip, and then the other lead is connected to the rotary file that's in the handpiece. So it knows that... point in time where the file is, and you're able to get a working link with some of the smaller files. Do you use hand instrumentation at all, even early on when you're trying to get access to a size 10 or 8 canal? It's very, very tiny. It's funny because it's a big debate at the school with the postdocs because I don't use hand files. I very rarely use hand files. It has to be a very, very classified case that I cannot even put a small little night-eye rotary file in there and work my way down. Then I only use the sizes 6, 8, and 10 in stiff file sizes. with the residents who kind of like to emulate i said look you guys have to work on hand files first you got to get good at it before you move on to the no hand file so it's i personally don't use hand files much clinically but i still recommend because uh hand files being stainless steel compare compared to niti files are stronger so you are able to create a path for yourself a little bit more predictably with less uh chance of separation using a hand file even a small size like a six than you can with an eye tie rotary file so it's a good idea at the beginning to use a couple of hand files to create a map i'm glad you said that I know when I practiced endodontics, I could not do a tough case without a hand file. And I would take a number 10 hand file and cut the tip off because it made it a cutting edge. It made it active. Yeah, it made it active and just threw some EDTA on there after I used a Stewart probe to actually chip away to find the canal. I don't remember. George Stewart, do you remember him? Yeah, of course. Of course, George Stewart. Yeah, he was my instructor. So was I.B. Bender. In fact. This is going to really get you. The last person that did a research paper, we didn't finish it. Louis Grossman did a research paper with a pen. Louis the Root, right? It was called Louis the Root in 1984 and a half, something like that. He passed away during the time I was doing that project with him. That was the last research project he was doing. We never published it. And then he passed away. I actually went to Penn dental school last year with my family and saw his picture up in the, in front of the main clinic. And it was, it reminded me of a picture from someone from the 1800s, you know, it was one of those portrait pictures. And I told, I showed my kids, my kids looked at the picture and it looked like the guy was living from the 1700s. And I said to him, I actually did a research project with this guy, Louis, the founder of endodontics. And my kids are in their twenties and they're looking at me like, dad, you're so old. You know, it looked like George Washington up there. Awesome story. And he really did a nice job with the school, Penn Dental School. I have not been to Harvard where you are, but I don't know what it looks like or what it's like, but I'm sure it's quite a place to be. Yeah, we've got a bunch of museum of dental tools and all that stuff over there too. Yeah, so next time I'm in Boston, I'll make a visit. But Dr. Nasseh, it's been absolutely phenomenal talking with you. Thank you for this four-part series. I'm sure our listeners will appreciate the insight. Again, please visit Real World Endo. That's real, R-E-A-L, world, endo, all one word. And you can get to see videos, podcasts. Dr. Nasse is a real entertainer and he'll teach you endodontics. If you want to learn the insight of endodontics, just log onto his website or create an account and you'll have a lot of fun. Dr. Nasseh, it's a pleasure to have you on our show and we'll look forward to more great stuff that you're going to work with us on at Viva Learning. Thank you so much. Thank you so much, Phil. Have a great one.