Episode 202: Dr. Courtney Donkoh: How Does Your Mandible Grow?

Hi and welcome to episode 202 of the Untethered podcast. Today we have Dr. Courtney Donko joining us. Dr. Donko is a dentist with special interest in craniofacial growth and development. She strives to understand how environmental and lifestyle factors influence the structure of our faces and jaws. Much of her professional focus is dentofacial orthopedics in children. Dr. Donko's practice is located in the western Chicago suburbs. Quick disclaimer all information, content and material of this podcast are the opinions of, of the speakers and is for the informational purpose only and not intended to serve as a substitute for the consultation, diagnosis and or medical treatment of a qualified healthcare provider. Welcome to the Untethered Podcast. I am your host, Hallie Balkan. I'm a certified orofacial myologist, feeding specialist and mentor. This podcast is all about getting your questions answered and collaborating with colleagues to bring you the most up to date information in the orofacial myofunctional therapy, tethered oral tissue and airway space. I challenge you to keep an open mind and join my mission to get this information out to the masses.

Let's get started. Courtney, welcome to the podcast.

Thank you. Thank you for having me. I, I'm a little surprised I'm here actually, because I, I've listened to some of your other guests. I'm like, yeah, I know them. I know some stuff. You've had some of the celebrities of the airway world on. So I'm just, uh, I'm really humbled to be part of it.

Um, I think it's really fun to cross paths with different providers on social media. And then I, I hear names through colleagues and you know, for me it's less about like how famous or, you know, celebrity somebody is and more so like the changes that you guys are all making in their lives. And I, I know like just from following your account on Instagram, I was like, oh, we've got to get you on the podcast. Like, this is, you know, you're doing incredible work. I just love, I love everything you're sharing. So, you know, I, I kind of put you up there on a pedestal with a lot of these others.

So.

So anyways, I always, I usually start with asking people how they got into this space. But you had sent an article because we always ask for any interesting articles with our speakers. You sent an article, article on mandibular rotation revisited and like, what makes it so important? And when I, that, when that popped into my inbox, I was like, I keep hearing this term Come up and, you know, I know I've heard it from several individuals who've been on the podcast who have, you know, taught that I've, I've attended trainings with. But I want to start there because I don't think our listeners have a grasp on what mandibular rotation is, what it means, what the implications are. So I want to turn it over to you and kind of let you as the expert on, you know, this, because this is out of my wheelhouse. Um, share with us, you know, if you can start with what mandibular rotation.

Is and, and why we need to.

Know about it, why it's so important, I think that'll be really help. Helpful.

Yes. Yeah, I, I will absolutely go there. If you don't mind if I back up just a little bit. Yeah. Before that. So the article I sent you was a 2014 article by Peter Boucher. Um, and he does a lot of research at Texas A and M in the orthodontic department. So I would encourage anyone to read some of the Busheng literature to better understand, understand facial growth and development. So that said, I've always, since I was in dental school, been interested in growth and development of the faces and interested in anthropology and things like that. So approach, you know, now the ERA. So I graduated dental school in 2014. And, you know, there is discussion on airway at this point, you know, and a lot of, you know, thought leaders in that community are talking about maxillary growth and development, and they're talking about alterations in the oral posture that lead to the maxilla not growing as wide as it ought to and being more oriented in a lower position. So more of this vertical growth and then the, you know, the downstream implication of the mandible growing with a more downward or a backward rotation. And that was my, that was my entry level introduction into, you know, the general, you know, thought behind this facial growth. And I think that those are really important points, but I think that's not the entirety of the story. So fast forward a few years. I'm introduced to another group, a very, very TMJ focused group. And there's a lot of discussion here on the structure of the TMJ and alterations of that structure. So things like disc dysplas placements and condylar resorption or erosion of the condylar bone. And the discussion amongst this group primarily revolves around the sequence of a disc becoming displaced due to ligament stretching or tearing. Typically, there's a lot of talk about macro trauma, whiplash injuries, and compression injuries. You Know, to the chin, car accidents, things like that. Disc becomes displaced, condyles overloaded, condyle sails to. To achieve proper growth dimensions. And now we have a short ramus length and a kind of downswung mandible and the maxilla solos suit. So kind of two. Two different, you know, ideas on, you know, what's. What's going on. You know, I want to say I hate. I hate to make divisions and put people into camps. I really do. But the, you know, this kind of airway philosophy where poor breathing leads to this altered oral posture, you know, leads to this more vertical growth, neural growth pattern versus trauma, leads to joint injury, leads to poor mandibular growth, again, leads to this same type of growth pattern where it is narrow and retronasc. So those. And, and, and I'm trying to put on a list together, you know, and there are some people that say, well, do we care about the etiology? Let's just treat it. And like, I care. I care about the etiology because I'm really interested in babies and toddlers and children and is any of this preventable? You know, is there something we could do? So I really got focused on trying to consume anything I could to teach me more about both. Enter mandibular rotation. So a lot of the discussion in that bushing literature, and he, he references a lot of Bjork literature, is the. The pattern in which the mandible is growing. So I think all of your viewers know that unlike the maxilla, the mandible has no suture, and so it doesn't grow intrinsically. The mandible changes size and shape from infancy to adulthood by remodeling at the border. So along the border of the mandible, so lower border here, the posterior aspect of the ramus, you know, up at the condyle, there's areas of bone resorption and there's areas of bone deposition as mandible grows. And you know, that that pattern looks different in different individuals. So, for example, the individual that has more of a prominent chin and more of a square jaw lies, you know, the, the more attractive, you know, face, if you will. Typically, those types of growers, they. Their mandibles have grown with a more of a. Of an upswing or a forward rotation, as we call it, some would say a counterclockwise growth pattern. When you study that growth pattern, you'll notice that, for example, the condyle grows with a different trajectory as compared to the individual that has a retrognasic mandible. More of this downswing in Vertical growth, a very retrusive chin. So the good grower, that condyle actually grows with a superior and an anterior trajectory. So the condyle grows up and forward. That elongates the ramus and lowers the mandible. And then there's also lowering of the fossa in which the condyle sits in through growth of that cranial base. And, and it's just remarkable when you start looking at the, you know, the different patterns of growth. And we, most people talk about condylar growth, but most people aren't making any type of distinctions between like growing with a, with a posterior trajectory or an anterior trajectory. So you know, to contrast that good grower, the, the people that we see that many times have compressed pharyngeal airways and with very, you know, little chin projection and long lower facial thirds because of maxwing. Oftentimes you see that condylar growth in the condyle gets smaller superiorly, but, but toward, grows towards the posterior aspect of that foss. And so I think that that literature, at least for me reading it, like it took a long time to sink in and then understand like, okay, well how do you know? How do I see that? Because many times in classical orthodontics, when we want to do comparisons from one time point to another, we'll take two lateral CEPHs and superimpose them on the S end line so the anterior cranial base. And I learned that to assess the change of the mandible, that's not a good superimposition. And that really the mandible should be superimposed on structures in the mandible that, you know, are kind of static or stable over tonic. Back decades ago, when Bjork was doing his studies, he drove metal implants into the body of the mandible. You can't really do those same types of studies today. And so stable structures are often, you know, the inferior alveolar nerve, the border of that, the anterior border of symphysis. So to superimpose the mandible then you can, you can see change more reliably over time. Of course, now, today we have convenient CT and three dimensional imaging technology which, you know, definitely can change how we visualize things. But I would say that, you know, trying to understand natural growth and good growth of the face has revolutionized my thought process as a provider.

I mean, I think it's incredible and you explain things so beautifully. Like it just, I mean, I know there's a lot of like medical terminology in there, but for somebody who's in this space, you know, the examples you give and the direction that you explained to dogs growing versus how we want it to grow, the mandible in particular. I think it's very helpful to even understand both schools of thought, because my first, you know, my first reaction to you even saying that was, okay, well, what if both are true? Like, what if both are contributing to this? What. You know, how to. How do we determine that? Because shouldn't that also impact our approach? Like, don't we want to know. Like you said, you want to know.

The etiology, so we know we can.

We want to know if we can prevent it. But also treating the root cause, I think having a better understanding, and maybe in certain patients, we never will truly know, like, what came first, the chicken.

Or the egg, like, why. Right.

You know, but, you know, I think it does influence our treatment plan sometimes depending on the patient. So, you know, that kind of takes me to my next question. Question is, now that you've. You've kind of taken this deep dive into this space, and, you know, I know there's still so many questions to be, you know, asked and answered, even as a provider, I'm sure, what is your approach? How has it changed your approach or. Or how have you taken, you know, an approach from the beginning to address this and make sure that that mandible is, you know, in a healthy place for that patient? Because, you know, as a. As a provider, a speech pathologist, a feeding therapist, a myofunctional therapist, you know, I see patients where there's so many different schools of thoughts around what appliances to use and what treatment plan to follow and what comes first and what should be next. And I always go back to, well, if we're here, you know, if we're concerned about where the mandible sitting, right, and the mandibles sitting too far, it's too, you know, it's retrognathic, like you said, it's compressing on that pharyngeal airway space. If we've got these issues at hand, why are we only focused on the maxilla? You know, and. And that's not everybody, but that's some providers, and then there's others who say, oh, if you treat the maxilla, the mandible will follow. And then there's providers who, you know, my provider for my children down here, we moved about a year and a half ago and went into additional early expansion for my kids. You know, her whole plan did talk about, like, the placement of the mandible. So while we're doing certain Expansion, forward growth, you know, lateral growth and expanding on three planes. We also need to pay attention to where the mandible sitting during this process. And so yeah, I'm just super curious to hear, you know, what your approach is and you know, how this has really influenced that functionally in day to day practice.

Sure, yeah. Well, gosh, thanks for asking my opinion. I certainly don't have all the answers and I don't know that anyone does. And I've always said you can never have one guru. So I've certainly taken things from, you know, all my mentors and people I've attended continuing education with to try to put it all together. So, you know, I think, you know, the root of your question is like how what's my treatment approach? Or how do we help support the best growth and development of our young ones that we can. So, so certainly, you know, transverse expansion has become a really widely used and important tool when treating a lot of kids growth patterns. But the width or the transverse component, while it's very, you know, popular to address that, it is, it's not the, the only component of growth that's important. You know, this, this vertical component and controlling that is, is extremely important as well as trying to, to drive a more anterior growth pattern as well. So I don't know that it's, you know, only one thing or, you know, completely within the, the practitioner of the dental facial orthopedics. I don't know if it's completely within their control. But when talking about mandibular growth, you know, and trying to, like I said, control it or support it, I do want to, you know, bring in the discussion of functional appliances. There's a million different functional appliances. Some common names are Herbst, Twinblock, Mara, essentially the typical, you know, functional appliance, whether it be six like a hertz or removable, you can take it in and out like a twin block. It's typically something that's interarched. So there's one component that has anchorage on the maxilla or the maxillary molars, maxillary teeth. And there is a component that, you know, is, is anchored on the lower. And so the mandible is pushed forward or protruded forward by leverage that's gained from, from the upper jaw. And so most people who have used functional appliances or you know, read literature on them will pretty much agree that there is usually some distillation or kind of pushing back of the, you know, either the maxillary dentition, some will say the maxilla as a whole, but some type of distalization because your anchorage is there, as we are kind of pull, pulling the mandible forward. Well, I'm somebody who bought a practice that has quite a legacy of TMJ imaging, which I've adopted a lot of that. So I've seen hundreds of combin CTs and MRIs of TMJs in multiple positions. And so, you know, what do we know when we protrude someone's mandible forward a few millimeters? You can watch that condyle come down the articular eminence and out of the fossa, holding the condyle in that position, you know, by means of a hertz, et cetera, for, you know, six to 12 months. What kind of growth pattern does the condyle exhibit? Well, typically, that more superior and posterior type of growth, that was the growth pattern I was talking about earlier. That's associated with more of a. Of a vertical, more of a downward rotation of the mandible. So not only do we have the potential distillation of the. Of the maxillary teeth, but we are also maybe not creating such a favorable growth pattern for the mandible, even though that is the goal of many of these functional appliances. Like I said, particularly herps. But I don't want to, you know, get focused on a certain name, is that we have a retrognathic mandible. We have a Class 2 relationship right, where the mandible is further setback, and we're trying to correct that. Class two. And you often can achieve class two correction with a functional appliance, but it's not having a positive effect on the skeletal growth, on the. On the. The type of skeletal growth pattern that we want. It's. It's achieving more of a dental alveolar compensation. So have I used functional appliances before in my practice? Yes, I have. Do I think I'll use a functional appliance again? Probably not. And so you said, you know, how has this changed your treatment approach? Well, I'm trying to understand how good growth happens naturally, you know, without intervention, and then try to. To replicate that. So I will say that Simon Wong is someone that's been quite influential in some of my thought process. So in terms of, you know, supporting good mandibular growth and how his treatment pro. How my treatment approach may be, you know, altered is I think that the support of the myofunctional therapist of the, you know, that type of person working with the patient is so important because I am convinced that good oral resting posture has a massive effect on mandibular rotation and mandibular growth. And I was so tickled when I would read these studies that are published in notable orthodontic journals talking about mandibular posture. There's another one Haley, I have to send to you after this, and it comes from my dental school, University of Iowa. Now it's a non human study. It was, it was done on, on pigs. But it's still, you can still learn a lot from it. What they did with piglets is they fixated the maxilla to the bones superior to it. So basically they fixated across the suture so the maxilla could not grow vertically anymore. They limited the vertical growth of the maxilla by plating hardware across the sutures. And they studied the effect on the mandible. And what they found was these piglets and of course, pigs, this is a great control group because you have the same environment, you can feed them the same diet, you know, you can control them a little better than human. And the effects on the mandible in the piggies that their maxillas were not allowed to grow vertically any longer was, they had smaller gonal angles, they had more of an upswing in the mandible. They were the forward rotators. So, you know, those, those types of things are, are just fascinating. So I am a little off track, but.

No, no, I think it's, I think that's amazing and really interesting to hear about. Even if it's, you know, you know, on a, a little set of pigs, little piglets, because it's, it's still anatomy, it's still growth, and it still, I think, gives us some insight into what would happen, you know, if we had a human sample that we, we trial this on too. I think that's really, I think it's really fascinating.

So I guess kind of to sum it up is I, I, people talk about, do you expand the mandible? Do you not? I, I often do expansion of the lower arch. I do, but I think maintaining a good oral posture with the teeth and light contact, the posterior part of the tongue up against, sealed up against the palate and the lips closed, and how the muscular slings of the masseters and the temporalis muscle hold the mandible up, I think that is a powerful thing as far as trying to promote good mandibular growth.

So, and I might have missed this, but which appliances do you use or do you recommend then to achieve this?

Okay, yeah, great question. So I will say I, I try to be appliance agnostic and I think there is no one size fits all. So in my practice, I do frequently use a bioblock and you know, everyone has their own little version of, you know, this appliance. But I, I would just say it's a removable acrylic based appliance and I use that frequently. I also sometimes use a fixed appliance, so like a RPE rapid palatal expander. Some would say, hi Rax. I use both of those. And you know, it's kind of a, I make my decision based on, you know, the compliance of the patient, based on the compliance of the family. There are a few other factors too. But what I do like about the bioblock or the removable acrylic based expander is if it's well made and you know, you, you are pretty good with the techniques, you can have it function almost like a fixed expander in that, um, there's really no play. You know, you can get them extremely retentive. And I think that's where sometimes removable expanders maybe get a bad name, you know, in that they're, there's a little rock to them or a little wobble or they're not super retentive. And you don't have this, you know, kind of rigid fixation as you would with a cemented appliance. And so some will say, well, you're not getting as much sutural expansion when we're talking about the maxilla or you're, you're just, you're getting more tooth tipping, you know, when you, when you have those. And I think it definitely does depend on the, how well made the appliances and how skilled the practitioner is that's using it. But what I do like about those appliances is the control of the front teeth. So I treat many children in the primary dentition and the early mixed dentition. And many children that I see not only need transverse width, but there is a component in the anterior that is incorrect. So many times I'll see four or five, six year old that have extremely deep bite. So when they bite down, you don't see any of the lower front teeth, extremely deep overbite. And that was my youngest.

Yeah, my four year old.

Right. That's very undesirable in terms of growth. So if you have something fixed in there that you turn with a key, you can get really good lateral development, but it can be hard to open up that deep bite. And so sometimes I've, on those I've started using like little whip arms that lie behind the anterior teeth, you know, to try to bring them out forward. But those are very hard to activate in an absolute.