Expand podcast: Aligners and the predictability triad

This transcript has been reviewed by AI and may contain inaccuracies.

Welcome, everyone, to Expand Podcast, a DSD podcast about ortho insights. My name is Dr. Daniel Ramos, and today we have an interesting topic about aligner predictability. We are going to discuss the predictability pillars with someone I really admire, someone I consider one of the best orthodontists treating with aligners. I can also say a friend because we’ve already had some beers together, and we have a lot in common, right? We both came from South America, very close to one another. I come from Porto Alegre in the south of Brazil, and he's from Córdoba, Argentina. Right, Martín Pedernera?

Dr. Martín Pedernera:
Absolutely right.

Dr. Daniel Ramos:
Welcome, thank you so much. Today, we’re not going to talk about barbecue and pizza; we’re going to talk about aligners, just so you know, okay? Welcome to Expand Podcast, it’s a pleasure for us to have you here.

Dr. Martín Pedernera:
Thank you so much, Daniel, for the invitation. The pleasure and the honor are absolutely mine. You know, from the first moment you mentioned this idea and this plan you had, I was excited. As you said, we are friends first of all, and then we are colleagues, so I’m really looking forward to this. Thank you, my friend.

Dr. Daniel Ramos:
Thank you so much. Well, I chose this topic because it’s a very vast and complex subject. As orthodontists, I don’t remember ever using the word "predictability" when I was practicing with braces, right? Mostly because when a patient came into my clinic, I would start planning, simulating things in my mind, and imagining the final outcome. But we couldn’t really compare the results because it was all an idea in our heads. We used reference points to move to Class I, correct midlines, and most of the time, even the patient didn’t have a clear understanding. I would explain it by saying, “It’s going to be good, it’s going to be like this other case,” and so on. But the concept of predictability is something new that aligners brought to us.

Now, when we start reading about it, we find a lot of data talking about the predictability of aligners, and some doctors use these studies to say, “Well, it’s only 50% or 40% predictable.” We’ll talk more about these numbers soon. But many argue that, “I could have done better with another system; it’s not working.” And I want to discuss this with you because I don’t agree with that at all. I see your cases, I see my cases, and I see the cases from doctors working with DSD, and we are treating patients with aligners with great outcomes. So, to say it’s not working, we know that’s not true. But my first question for us to start is: Are aligners predictable?

Dr. Martín Pedernera:
For sure! When you mentioned that, it reminded me of something I often say when I lecture. I don’t remember ever going to a Congress on fixed appliances—whether it’s about the technique, the brand, or even lingual orthodontics—and hearing the word "predictability." Is this predictable? Is this not?

One of the key differences is that fixed appliances are bonded into the patient's mouth, which reduces a lot of the need for patient cooperation. That’s important because we’ve all had those braces cases where the patient comes to the office with one, two, or three brackets debonded. Is the archwire still producing the effect we wanted? No, that was a nightmare! We’d have to rebond the bracket, and the treatment wouldn’t be progressing as expected. But with fixed appliances, if the braces stay bonded 100% of the time, they’ll produce the desired result. Of course, our ability to bond the brackets in the correct position also plays a role in the outcome.

Now, with aligners, we’re dealing with a whole new variable: patient cooperation. Aligners themselves are predictable, but they depend on the patient wearing them as prescribed. Now, let me ask you, Daniel: How many of your patients do you think wear their aligners for the full 22 hours a day?

Dr. Daniel Ramos:
Honestly? I wouldn’t put my hands on fire for that!

Dr. Martín Pedernera:
Me neither! And that’s the point. One of the biggest factors affecting predictability is patient collaboration. We’re imperfect doctors, working with an imperfect device (the aligners), treating imperfect human beings. So why do we expect perfection?

Now, getting back to the question—are aligners predictable? Yes, they are. But many other factors come into play. There are scientific papers that provide data on the predictability of certain movements, but they don’t always agree with each other. One study might say a movement is 80% predictable, while another says 83.7% or 92%. Which one do we believe?

Ultimately, we need to rely on our own experience. The patients in those studies are not the same as mine or yours, and we don’t know if they followed the instructions for 22 hours a day. So many factors affect predictability, but I can tell you from my experience that aligners are definitely predictable. However, we need to understand the factors that influence predictability and work to improve them.

Dr. Daniel Ramos:
You’ve already mentioned one of the pillars of predictability: patient collaboration. This is a factor we can’t control, but I agree with you about the importance of connection. We need to create a relationship with our patients, motivate them, and use technology to help them understand the importance of wearing their aligners. Only then will we see better outcomes, because the aligners inside the box aren’t going to move teeth on their own.

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Dr. Martín Pedernera:
Absolutely, the aligners won’t do anything sitting in the box. The second factor we need to consider is the technical side—biomechanics. Every orthodontist should understand how to make plastic work. While it’s not exactly the same as using braces, we need to use our knowledge of biomechanics to ensure similar efficiency. I don’t imagine the periodontal ligament looking up and saying, “Oh, it’s plastic, so I won’t move because I only respond to braces.” The periodontal ligament doesn’t care what material is applying pressure—it’s just going to respond to the right force in the right direction. The key is to understand how to apply those forces with aligners.

When I read a paper saying that intrusion has a 30-40% predictability rate, I don’t see it as proof that the technique doesn’t work. Instead, I see it as an opportunity to create a strategy. For example, one thing I’d like to discuss is the use of overcorrection, something we always did with braces. When we needed to intrude a tooth, we would overbend the archwire to apply the necessary force. With aligners, we can’t physically bend the plastic, but we can simulate the same effect in the software by overcorrecting.

How do you use overcorrection, Daniel? Do you think it’s a useful tool for improving outcomes?

Dr. Daniel Ramos:
I absolutely agree with you, Martín. Overcorrection is something we can use to improve the outcomes of our aligner treatments, just like we did with braces. The studies you mentioned don’t typically factor in overcorrection, which is a key part of the strategy. Just as we overbend wires with braces to get the movement we want, we can plan for overcorrection in the digital treatment setups for aligners. This is a crucial part of making the aligners more predictable.

I’d like to hear your thoughts on this too. How do you use overcorrection in your practice, and how do you think companies are adapting to this concept to improve the capabilities of artificial intelligence?

Dr. Martín Pedernera:
I definitely use overcorrection. As you mentioned, it’s something we did even with fixed appliances, especially with lingual braces, where everything is bonded indirectly. We had to overcorrect rotations and other movements to get the desired results. There was a famous paper by Dr. Roth that talked about the loss of force in archwires during movement. When a tooth is 45 degrees rotated, the archwire exerts a lot of force, but once the tooth is only 2 degrees out of position, the wire can’t apply the same amount of force to finish the movement. That’s why we had to incorporate overcorrection.

In clear aligner therapy, I do the same. It’s not a new concept, and it’s a necessary tool for improving outcomes. Just as we overcorrected with braces, we can use the digital treatment software to plan for overcorrection with aligners. It’s all about understanding the limitations of the materials and working within those limitations to achieve the best possible results.

Dr. Daniel Ramos:
Exactly. We have to adapt our knowledge of biomechanics to the new tools we’re using, whether it’s braces or aligners. We can’t expect perfection from any system, but by understanding the principles behind tooth movement, we can create strategies to overcome challenges.

Now, I want to move on to a tricky question. I’m going to ask the same question twice but with a slight variation, and I’d love to hear your thoughts. The first version is: Can we treat all malocclusions with aligners? The second version is: Can we treat all malocclusions only with aligners?

Dr. Martín Pedernera:
That’s a really interesting distinction. To the first question—can we treat all malocclusions with aligners?—I’d say 100% yes. There’s no malocclusion that can’t be treated with aligners. We’ve seen amazing cases, from surgical patients to impacted teeth, and even cases with maxillary expansion or growing patients. Aligners can handle everything: deep bites, open bites, Class II, Class III—you name it, aligners can treat it.

But to the second question—can we treat all malocclusions only with aligners?—the answer is 100% no. Whoever says they can treat every malocclusion only with aligners, I find that hard to believe. Aligners are powerful, but they have limitations. Some movements, like canine rotation or extrusion, are not as predictable with aligners alone. In those cases, we need to incorporate auxiliary techniques.

For example, if we’re dealing with an impacted canine or a patient who needs extractions, we need to use auxiliaries like TADs, power arms, or even sectional wires. I always tell my patients up front that while aligners are the main tool, if we need to use something else to achieve the best result, we’ll do it.

Dr. Daniel Ramos:
That makes a lot of sense, and it’s a good point. Even with braces, we often needed to use auxiliary devices like TADs, elastics, or expanders to achieve certain movements. The same is true for aligners. The software might simulate a movement, but it’s up to us as clinicians to determine whether that movement is feasible in reality.

You mentioned earlier that you classify cases as A, B, or C, based on the need for auxiliaries. Could you expand on that and give us an idea of when you would go hybrid with aligners versus when you might treat a case with aligners alone?

Dr. Martín Pedernera:
Sure! I like to classify cases in terms of their need for auxiliaries. Category A cases are those that can be treated with aligners alone, without any auxiliaries. Category B cases are those where auxiliaries aren’t strictly necessary but can help reduce treatment time or improve outcomes. And Category C cases are those where auxiliaries are absolutely mandatory, like surgical cases or cases with impacted canines.

In my clinic, I’d say about 90% of my cases involve some form of hybrid treatment. Whether it’s buttons and elastics, TADs, or sectional wires, most cases benefit from some form of auxiliary device. For example, if I’m treating a Class II patient with a deep bite, I’ll need to consider whether I need intrusion of the anterior teeth or extrusion of the posterior teeth, and I’ll plan my auxiliaries accordingly.

The key is to thoroughly diagnose each case and understand the range of movement required. For some patients, you might only need to distalize a few millimeters, which is achievable with aligners alone. But if you need to distalize more than that, or if the patient has other complex movements, that’s when you need to bring in auxiliaries.

Dr. Daniel Ramos:
I love that you used the analogy of planning a trip. Depending on where we’re starting from and where we’re going, we might need to take a plane, a car, or even walk part of the way. Aligners are like one mode of transportation, but they’re not always the best option for the entire journey. Sometimes we need to combine different tools to get the best results.

I also agree with your point about patient communication. We need to offer our patients all the available options, even if they seem like they might be too much for the patient to handle. It’s their decision in the end, but we need to offer the best solutions based on our diagnosis and the limitations of the aligners.

Let me know if you'd like me to continue!

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Sure! Here is the fully edited version of the transcript, with all the requested adjustments:

Dr. Daniel Ramos:
Welcome to episode five of the Xpand podcast. Today, I will be speaking to Dr. Martín Pedernera about the predictability of aligner treatment. Martín is an experienced orthodontist with aligners, and I’m sure you’ll be very interested in what he has to share. Enjoy it!

Welcome everyone to the Xpand podcast, a DSD podcast about ortho insights. My name is Daniel Ramos, and today we have an interesting topic about aligner predictability. We are going to discuss the predictability pillars with someone I really admire, someone I understand is one of the best orthodontists treating with aligners. I can also say he is a friend because we have shared a few beers together, and we have a lot in common, especially where we come from in South America. I am from Porto Alegre, in the south of Brazil, and he is from Cordoba, Argentina. Welcome, Dr. Martín Pedernera!

Dr. Martín Pedernera:
Absolutely right, Daniel. Thank you so much. Today, we are not going to talk about barbecue and pizza; we are going to talk about aligners! Thank you so much for the invitation. The pleasure and honor are absolutely mine. You know, from the first moment you mentioned this idea and this podcast plan, I was excited because, as you said, we are friends first and colleagues second. So, I’m really looking forward to this.

Dr. Daniel Ramos:
Thank you, my friend. I chose this topic because it is vast and significant. When I was practicing with braces, I don't remember ever using the word "predictability." It wasn’t something we discussed. When a patient came to my clinic, I had a plan in mind, and I would simulate it mentally, imagining the final outcome. But once we achieved that outcome, we had no way to compare the initial idea to the result, because it was all based on our mental simulation. The predictability we now talk about is something new, brought to us by aligners.

We now have lots of data on aligner predictability, with papers showing statistics like 50% or 40% success rates for certain movements. Many doctors use these numbers to argue that the system doesn't work as well as braces, but that's something I can’t agree with. I’ve seen your cases, Martín, and my own, as well as cases from doctors working with DSD, and we’re getting great outcomes. To say aligners don’t work isn’t true.

So my first question is: Are aligners predictable?

Dr. Martín Pedernera:
For sure. You mentioned an important point: back in the day, with fixed appliances like braces, we didn’t really discuss predictability. When a patient came in with braces, we weren't measuring every little movement with such precision because it wasn’t needed in the same way. With braces, we have a fixed appliance bonded to the patient’s teeth, which reduces the reliance on patient compliance.

Now, with aligners, we depend heavily on the patient’s cooperation. For example, if a patient comes in with braces and has a few brackets that have debonded, the treatment isn't as effective. The same is true with aligners. If a patient isn’t wearing their aligners as prescribed, say 22 hours a day, the treatment won’t work as planned. In that sense, the predictability of the aligners depends on patient cooperation.

I also want to emphasize that we are imperfect human beings—imperfect doctors treating imperfect patients. So, while aligners are predictable, we need to manage our expectations and focus on controlling the variables we can. But yes, aligners are definitely predictable. It's just that, as with braces, we need to pay attention to biomechanics and patient compliance to achieve the desired outcomes.

Dr. Daniel Ramos:
You already mentioned one of the pillars of predictability: patient compliance, which we can't always control. And I love what you said about human imperfection. We can’t expect perfection, but we can aim for excellence. Aligners alone won’t move teeth. We need to motivate our patients, explain the importance of compliance, and use technology to track progress.

On the technical side, we need to understand how to apply the same biomechanical principles we learned with braces to aligners. Whether it’s braces or plastic, as long as the right force is applied to the right spot, the tooth will move.

When I read studies that say intrusion has only a 30-40% predictability, I don’t see that as a failure of the system. I see it as a need to create a better strategy. Overcorrection, for example, is something we used with braces to ensure the desired movement, and it’s something we can do digitally with aligners.

What are your thoughts on overcorrection, Martín? Do you use it, and how do you feel companies are adapting to this?

Dr. Martín Pedernera:
I absolutely use overcorrection. Like you said, it’s something we’ve done even with fixed appliances, particularly with lingual braces, where everything is bonded indirectly. Overcorrecting rotations or specific movements was necessary to achieve the desired result. Dr. Roth, for example, had a famous paper discussing the loss of force over time in archwires. As a tooth rotates closer to its final position, the archwire exerts less force, so overcorrection is essential.

In aligner therapy, overcorrection is also key. It’s not new, and it’s a strategy that works. We plan for it in the digital treatment setups, adjusting the simulation to account for the realities of tooth movement.

Dr. Daniel Ramos:
That’s a great point, Martín. Overcorrection is something that can make a significant difference, and we need to teach this to our colleagues who are transitioning to aligners. We must adapt the techniques we used with braces to this new digital environment. Aligners are a fantastic tool, but we need to understand their limitations and how to overcome them.

Now, I want to ask you a tricky question: Can we treat all malocclusions with aligners? And the second version of the question is: Can we treat all malocclusions only with aligners?

Dr. Martín Pedernera:
Great distinction! For the first question—can we treat all malocclusions with aligners?—my answer is 100% yes. We can treat any malocclusion, from simple cases to complex surgical cases, with aligners. Whether it’s deep bites, open bites, Class II, Class III, or even cases requiring maxillary expansion, aligners are capable.

For the second question—can we treat all malocclusions only with aligners?—the answer is 100% no. Aligners are powerful, but they have limitations, just like braces. Certain movements, like canine rotation or extrusion, are more challenging with aligners alone. In those cases, we need auxiliaries like TADs, sectional wires, or elastics.

I make it a point to explain this to my patients. I tell them aligners will do the majority of the work, but if we need to use an auxiliary to get the best result, we will.

Dr. Daniel Ramos:
That’s an excellent explanation. Even with braces, we often needed auxiliaries to achieve certain movements, so it makes sense that the same would be true for aligners. One mistake I see is doctors relying too much on the software and not considering the limitations of the system.

You mentioned classifying cases as A, B, or C based on the need for auxiliaries. Could you expand on that and tell us when you would use a hybrid approach with aligners?

Dr. Martín Pedernera:
Sure! I classify cases as A, B, or C, depending on whether auxiliaries are necessary. Category A cases can be treated with aligners alone, without any auxiliaries. Category B cases can be treated with aligners alone, but using auxiliaries like power arms or sectional wires can reduce treatment time or improve outcomes. Category C cases absolutely require auxiliaries, like surgical cases or those with impacted canines.

In my clinic, I’d say about 90% of cases involve some form of hybrid treatment. Even simple cases may benefit from elastics or power arms, and for complex cases, auxiliaries are a must.

The key is diagnosing each case thoroughly and understanding the range of movement required. For example, if you need to distalize a tooth by 2 millimeters, that’s achievable with aligners alone. But if you need more than that, or if the patient has a complex case, then you’ll need to bring in auxiliaries.

Dr. Daniel Ramos:
I love your analogy about planning a trip. Depending on where we’re going and how far it is, we might need different modes of transportation. Aligners are like one tool, but we need to combine them with others to get the best results.

And I agree that we should never assume a patient won’t want to use auxiliaries. It’s our job to present all the options and let the patient decide. If they don’t want to use certain devices, that’s their choice, but we shouldn’t make that decision for them.

As we wrap up, Martín, what would be your final message for our listeners? What’s the key takeaway when it comes to aligner predictability?

Dr. Martín Pedernera:
I’d go back to the three main pillars we discussed: the patient, the aligners (including the technique and system), and the orthodontist. These three factors must work together. If one of them fails, the entire treatment can suffer.

We, as orthodontists, need to diagnose thoroughly, plan effectively, and use all the tools available to us. Patients need to be motivated and compliant, and the aligner system itself must be high quality. With all these elements working together, we can achieve predictable outcomes.

Dr. Daniel Ramos:
Thank you, Martín! That’s an amazing message. It’s so important for doctors to understand these pillars of predictability. Thank you for sharing your insights with us today.

To everyone listening, I hope you enjoyed this episode of the Expand podcast with Dr. Martín Pedernera. See you in the next episode. Bye-bye!