Episode 130: 4D Printed Aligners – Are Shape Memory Aligners Worth It?

Eon Engelbrecht, E-Radio-SA [00:00:04]

Welcome back to Save Your Money, Save Your Teeth, where we look at what genuinely protects your teeth and also your wallet. So last week we spoke about production dentistry, how to protect yourself from it, the big rush to treatment plans that suit the practice more than the patient, and today we’re looking at genuinely new technology and how to judge it without getting swept up in the hype. Clear aligners have changed how adults straighten their teeth.

Now there’s a new generation of aligners printed directly by a 3D printer from plastics that remember their shape, with features the old ones simply couldn’t have. Some people are calling it 4D printing, and overseas the same technology is already changing how children are treated. So today, what does 4D actually mean?

Who’s making these aligners, and what can they do that the old ones cannot do? Are they safe to wear all day, and what’s coming for the kids? Joining me as always is Dr Clifford Yudelman from OptiSmile in Sea Point, Cape Town.

Dr Yudelman, welcome back.

Dr Clifford Yudelman, OptiSmile [00:01:12]

Thanks, Eon, great to be back. Today should be pretty interesting.

Eon Engelbrecht, E-Radio-SA [00:01:16]

Now, we already know what 3D printing is. What on earth is 4D printing in dentistry, doctor?

Dr Clifford Yudelman, OptiSmile [00:01:24]

So 4D, it’s an interesting term, isn’t it? So basically 3D printing is about the shape, but the fourth dimension is time, meaning the object is designed to behave in a certain way after it’s made. So in dentistry, that mostly means that aligners are printed from a shape memory material, which holds its programmed shape, and then it keeps pushing gently instead of going slack.

I mean, 4D is partly like a marketing word, but the more accurate phrase is direct printed shape memory aligners. That’s where that comes from.

Eon Engelbrecht, E-Radio-SA [00:02:04]

Okay, and what’s the difference between an aligner printed directly and the conventional kind that most people have worn?

Dr Clifford Yudelman, OptiSmile [00:02:12]

So for people that haven’t listened to previous podcasts about aligners, maybe I’ll just give a little bit of an intro about what we’re talking about. So aligners, the most popular one in the world, they’ve done over 25 million cases in the last 25 years.

That would be the genuine Invisalign, which is available in South Africa. It’s the main one that we focus on at OptiSmile, but we do sometimes use other aligners that are made in a similar way, or sometimes in a different way, which we’re going to talk about today. And aligners are used to straighten your teeth.

They’re clear trays that fit over your teeth and apply pressure to your teeth, a tiny, tiny bit of pressure, and then after a week or 10 days or two weeks, depending on the type of aligner and your own case, you put the next one in, and so on and so forth. And after 10 or 20 or 30 aligners, your teeth are now straight, simply put, versus brackets and wires or railway tracks, which is traditional braces, where you’ve got wires and elastics and brackets.

So a conventional aligner, most times aligners are made by printing a model of your teeth from a scan and then heating a sheet of plastic and then vacuuming it or sucking it down over a model, just like cling film going over a bowl. If you imagine you turn a bowl upside down and you put cling film over the top, the plastic thins out unevenly as it stretches, and then every stage means two more models, and those models go in the bin. A directly printed aligner skips all of that. The printer actually just prints the aligner itself, and the thickness is exactly where it’s supposed to be, and then there’s less waste and a more precise fit.

And potentially there will in the future be a way that you could get your aligners the same day, rather than them being made in many cases overseas and then shipped, and it can take two or three weeks before you get your aligners. I don’t think that’s a big thing. If you’re going to wear aligners for 6 or 12 months, getting them today or in a few weeks’ time is not a big difference. I think that ties in with what we spoke about last week, which is pressure to sign a contract so you can start straightening your teeth today.

So go back and listen to last week’s one. Let’s keep going, because I don’t want to jump the gun like I usually do.

Eon Engelbrecht, E-Radio-SA [00:05:00]

Okay, my next question is, how does a shape memory aligner move your teeth differently, and also, is it true that heat changes its shape?

Dr Clifford Yudelman, OptiSmile [00:05:11]

Invisalign has done research over the years. They’ve spent hundreds of millions, if not a billion, already just on the type of plastic that they use when they vacuum form the aligners. Dr Harris at our practice actually went to a new Invisalign factory in Poland, and he watched how they make them. He also saw that, say we do a case where someone needs 30 aligners, that’s 30 upper and lower, so that would be 60 aligners, and so for every case there would be 60 models that are not recyclable. So when he came back, we started looking at these shape memory and 3D printed ones.

But back to the question. With a conventional aligner, depending on the material, if you get some generic one made in South Africa and you don’t know what material they’re making it with, most of the push that it gives to the tooth is in the first day or two, and then you’re supposed to wear it for another week or up to two weeks, and the plastic relaxes and the forces fade, and that’s not ideal for the biology. Shape memory materials are designed to give a lighter, more continuous force, supposed to be similar to a good orthodontic wire. And so with shape memory aligners, you can actually put them in hot water and they go very soft, and as they get to body temperature, they remember what shape they’re supposed to be, so they don’t distort. They keep pushing on your teeth.

There’s still a lot of studies out there and lab research, and independent studies are yet to show that the one works better than the other. There is a lot of research, obviously, that the manufacturers who are selling these things have paid for, so you always have to take a look at that. But you can’t make the teeth move faster than the bone can safely remodel. In fact, it goes against you. If you put very heavy wires and heavy elastics on teeth, you can actually cause root damage or root resorption, and also the bone can then resist and the teeth won’t move, and we’ve seen cases where this has happened. It’s very scientific, and it all needs to be a proper certified system that’s been properly researched.

Eon Engelbrecht, E-Radio-SA [00:07:43]

And who is actually making these, and is Invisalign also heading the same way?

Dr Clifford Yudelman, OptiSmile [00:07:49]

The two best known companies for printed aligners are Graphy, G-R-A-P-H-Y, from Korea, and they’re the ones that apparently pioneered the shape memory resin, and then there’s another one, LuxCreo, from California. That’s L-U-X and then a capital C, C-R-E-O, LuxCreo, which had the first FDA cleared direct printed aligner system, and they sell the whole package: the printer, the software, the material. There’s a big Chinese aligner company, Angel Aligner, that has now apparently invested in LuxCreo.

Overseas, Angel is very big. A lot of dentists who used to do Invisalign are switching to Angel, so it’s just like these Chinese cars in South Africa that are taking over. Angel aligners are very, very good. I’ve never used them myself, but if we could get them in South Africa, we would definitely give them a go. It’s interesting that Angel has now invested in LuxCreo, and also Invisalign’s parent company bought an Austrian 3D printing company, and they said that their goal is to print Invisalign aligners directly.

So Invisalign tends to move a lot slower. It’s a much bigger company and they’ve got a lot more at stake. We’ve heard about things that are coming from Invisalign two or three years before they actually launch them, but it looks like it’s going in that direction. They do get a lot of slack, or should I say, people throw a lot of issues at them to do with the environment and plastic going into the environment and the waste, so I think it’s more pressure from people that are concerned from that point of view, which is a good thing. So yeah, look, that’s where the whole industry is heading.

Eon Engelbrecht, E-Radio-SA [00:09:56]

And what can a printed aligner do that a conventional one simply cannot do?

Dr Clifford Yudelman, OptiSmile [00:10:02]

So that’s where it’s getting exciting, and that’s where I’m very interested. Because it’s printed rather than stretched, you can make it thicker exactly where you need more force, or thinner at the gum line for comfort. You can build bite ramps straight into the aligner instead of bonding them onto the teeth. You can print a solid replacement tooth into a gap rather than a hollow shell. And then for some movements you can thicken some of the parts of the aligner, so you can end up needing fewer or no attachments.

And to be fair to the conventional brands, they’re not standing still either. Spark, for example, is still a vacuum formed type of aligner, very, very good plastic. It’s right up there with Invisalign. We do some Spark cases at OptiSmile, and we think it’s a very good product, and they’re now building hooks for elastics right into the aligner instead of cutting a slot or gluing a button onto the tooth, because sometimes with aligners you use elastics. Now with a lot of the aligner companies, you can integrate the actual roots from a 3D x-ray, so you can see how the roots are going to move. So there’s a lot of stuff going on with 3D, and yeah, it’s very exciting.

Eon Engelbrecht, E-Radio-SA [00:11:31]

And then, doctor, I want to ask you, is it safe to wear printed resin in your mouth 22 hours a day? Have you seen any problems in the practice, or in practice?

Dr Clifford Yudelman, OptiSmile [00:11:42]

So this is resin. It’s not the usual plastic sheet. Even with the plastic sheets, there have been some concerns about microplastics and whether those are safe. There’s a lot of research going on all the time. The cleared materials have passed toxicity testing, and one of the studies, paid for by the manufacturer, found one of them even more biocompatible when made exactly to the manufacturer’s process. But the catch is the printing and the washing and the curing have to be done perfectly, and the resins can cause very bad sensitivity or allergic reactions in some people. We have heard of several cases where the lab that was printing them apparently did everything they were supposed to, but there’s very little margin for any kind of error when you’re doing 3D printing, and even one aligner can cause severe problems.

So I think any dentist that’s printing their own aligners in-house normally won’t be doing it themself, and they won’t have a technician. They might train one of their dental assistants, so that’s still a very big grey area. We were very excited. We were looking at doing that. We did a course, we were going to print our own aligners, and I’m always one to hold back a little bit and see where things move.

But if you’re wearing 3D printed aligners and you notice any irritation or burning or swelling… Even with regular aligners, we’ve had some patients who’ve actually had reactions, but that’s quite rare. People can react to different things. Some people are highly allergic to almost anything, so maybe aligners are not for them. They might even be allergic to the metals that are used on braces, so it’s an individual thing. It’s very exciting and new, but a practice should introduce these things carefully and then watch out for problems.

Eon Engelbrecht, E-Radio-SA [00:14:03]

And, doctor, what is changing for children? I hear that overseas there’s now a printed expander that replaces the old metal ones.

Dr Clifford Yudelman, OptiSmile [00:14:11]

Yeah, so Invisalign now makes a palatal expander that’s directly 3D printed. The previous old metal ones were cemented in, and then the parent had to turn a little key in the kid’s mouth every day. The printed version is a series of removable trays made from a digital scan, and they just widen the jaw step by step, and apparently it’s much better than the screw type. It’s in use in America and Europe and the UK and even in Australia, and they’ve been promising it to us in South Africa for over a year now, but we’re yet to see it. So if you’re from Invisalign and you’re listening to this, we’re waiting for these expanders. We think they’re fantastic and we will definitely use them. So unfortunately, in South Africa, children still have to get traditional expanders.

But what’s very exciting, that Invisalign needs to watch out for, is that Spark now has a junior system for children under 13. It works in two phases, and you can pause between them while the child grows, and it has all kinds of built-in features, something called BiteSync that encourages the lower jaw forward in children whose lower jaw sits too far back. There are a number of other features built into Spark Junior, and we’re definitely going to be using this at OptiSmile because of these exciting features. None of the locally made aligners have anything you can use for kids, so Invisalign First, or Invisalign for kids, was the only one available.

So now there’s this other huge company, Spark. The parent company is Ormco, and they’re very well represented in South Africa and very reliable, and their aligner materials are used worldwide and have a much longer record than any locally made ones. It’s amazing that all of these features are now available in South Africa. For parents, that means there’s no metal, fewer emergency visits to adjust braces or bands coming off, and also it’s a treatment that works in stages and with the growth, rather than waiting until everything’s all in and then putting braces on for five years or three years or whatever it is.

Eon Engelbrecht, E-Radio-SA [00:16:58]

And who is this suitable for, doctor, and also who should stick with conventional aligners or braces?

Dr Clifford Yudelman, OptiSmile [00:17:03]

You know, I think there’s going to be a big crossover between normal aligners and printed ones until all these other features, like what LuxCreo is doing, which gets very exciting with all the built-in ramps and many, many other features that are printed in them, and they do all the designs. Unfortunately, we can’t get LuxCreo directly in South Africa, but I’m watching that very carefully, and it could make things go a lot better and quicker.

At the moment, like I said, a lot of the research and the cases we see are from what we call KOLs, key opinion leaders, which means people that get all of this for free so that they can put the information out there in lectures and on Instagram. So we would want proper university studies, and it’s better if your dentist is a little bit more sceptical. But I’m very excited about LuxCreo, and printed ones will work better than traditional vacuum formed aligners when the time comes. I don’t think we’re ready yet, certainly in South Africa, with what we have available.

Eon Engelbrecht, E-Radio-SA [00:18:30]

And I have to ask you, will it make straightening teeth cheaper, and can it help with retainers, so the teeth don’t actually drift back?

Dr Clifford Yudelman, OptiSmile [00:18:37]

Maybe long term it will be, because there’s less plastic waste, when printing is perfected and not so technically driven that you can do them in the practice. I think it could get cheaper. In the short term, practices that are doing it are paying for very expensive printers, and a bottle of resin is 20,000 rand, so you’re not printing these things for free. In fact, the resin ends up costing a lot more than a special plastic sheet that you would vacuum form over a model.

Retainers, for me… I did actually buy some resin that was made especially for printing retainers, and I printed a set of retainers for myself. I’ve never had orthodontics. I did everything according to the instructions, and I put them in the hot water, et cetera, et cetera, and I put them in my mouth, and I was not very impressed with them at all, to the point that I never made any retainers for any patient. That bottle of resin cost me about 15,000 rand, and it’s now expired, so I learned the hard way.

So, look, if we have your models, we use something called Zendura A. It’s a very, very high-end retainer material used worldwide. Zendura seals each sheet of plastic in a special laminated bag with some stuff in there that stops moisture from getting in, and they’re not cheap. It’s a couple of hundred rand just for one sheet, and then you heat it up according to the directions and you vacuum it and you trim it. We’ve seen these retainers looking good after a year.

The thing with anything 3D printed is that they’re porous, because they’re made in layers. And the sheets, some of them are triple laminated. It’s like three pieces of plastic all in one sandwich. They’re very smooth, they’re clear, they don’t get smelly, they don’t pick up stain. Some of the 3D printed aligners that we’ve tried… In fact, we did get a trial case of LuxCreo, and it did work for the patient, but they were complaining bitterly about the staining. They go yellow within a day or two and you have to bleach them. So for retainers, I think it’s still going to be a way to go, unless there’s some new 3D printing method, rather than a liquid where the printer goes up and down and builds it in layers.

Eon Engelbrecht, E-Radio-SA [00:21:37]

And just one more question. Is this available now? Should patients be asking for it?

Dr Clifford Yudelman, OptiSmile [00:21:41]

Look, it is available, but like a lot of things, when you’re all the way down at the southern tip of Africa, you’ve got to wait longer. Remember, we only got television in 1976. I think I was 16. Remember we had Pop Shop, and then one night was English and one night was Afrikaans, and if there was nothing on, you used to sit and look at the test pattern, or listen to the radio. I might be giving away my age. People my age would know. But when we did get television in South Africa, it was pretty good. The whole world went with, I think it was PAL or NTSC, and obviously in South Africa we went the other way, unfortunately.

But eventually things do come to South Africa, and it’s always the cream that rises to the top. So when we do get these and they’re working nicely, I have no doubt that we’ll get the good stuff. But at the moment, I don’t think I would recommend people go and look for it specifically, and I would definitely ask questions. It’s just about what the future of orthodontics holds, and I find it all very exciting. We wanted to do this podcast today just to talk about some of these features that we’ve spoken about, and there are going to be a lot more podcasts about all the new changes that dentistry has to offer.

Eon Engelbrecht, E-Radio-SA [00:23:16]

Dr Yudelman, thank you so much. That was another very insightful episode of Save Your Money, Save Your Teeth, and we appreciate your time and your knowledge.

Dr Clifford Yudelman, OptiSmile [00:23:27]

Pleasure, thank you, and looking forward to speaking to you again next week.

Eon Engelbrecht, E-Radio-SA [00:23:33]

Absolutely. Until next week, thank you so much.

OptiSmile Announcer [00:23:57]

Discover the world of dental excellence with OptiSmile. Join us for a weekly podcast featuring Dr Clifford Yudelman, a seasoned expert with 40 years of dental experience across four continents. Gain unique insights and expert dental advice by visiting optismile.co.za for articles that illuminate the path to optimal oral health. If you’re seeking unparalleled dental care in Cape Town, get in touch with OptiSmile or book directly online on optismile.co.za. OptiSmile, where global expertise meets local care.