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What is the "orthotropic" explanation of partially erupt 2nd mandibular molars, and a deep bite  

Active Member

So i have a deep bite, in addition to my second mandibular molars being halfway erupt, halfway buried in the gums. 

This is not ideal development obviously,  because we should have room in our jaws for all teeth including wisdom ideally. 

Is this because of a lack of forward growth? Lateral growth? Idk I cannot understand. My IMW is identical to my brothers and dads, (measured using my retainers and theirs) at around 33-35 mm. Yet they look so much better than me and have all teeth in aside from wisdoms.


Posted : 23/10/2019 10:07 pm
Eminent Member

Orthotropics youtube channel has some good videos explaining the how and why of deep bites, and how they often result in partially erupted 2nd molars. I don't have the links right now(just google Orthotropics deep bite to find out), but here's my attempt at explanation.

My understanding regarding your case is that it all stems from the tongue. Check right now, where is your entire tongue, especially the sides of it? My guess is that the tongue, lacking sufficient intermolar width to stick to the palate without touching any teeth, is lightly sticking between your molars in the back. After a long time, imagine what that does...It pushes the 2nd molars on the mandible and the maxilla inwards, intruding them. As a result, your incisors overerupt to close the bite. And when you put your teeth together (without the tongue between the teeth) to check what your occlusion is, you got a deep bite. I recall Mike Mew saying that a lot of deep bite patients don't rest(ie resting oral posture) in a deep bite, but they rest with their tongue in between their molars and their incisors not in a deep bite position. It's only when an orthodontist asks them to bite together do you get that deep bite showing.

So the cause is ultimately a lack of lateral space causing your tongue to precipitate all these issues. I don't know about why your father/brother don't have the deep bite if they have the same intermolar width; it might be just that malocclusion is highly individual and manifests itself in different ways...or that explanation might just be a cop out, like how the orthodontists cop out and attribute almost everything to genetics.

Anyway, if you're going to get treatment as opposed to just mewing, you should be careful with how your orthodontist addresses the issue. Conventional orthodontics would usually address the incisor overeruption as the root of the problem, and push the upper incisors upwards and the mandible downwards, increasing lower facial height unfavorably(an unavoidable consequence, the textbooks say). An orthotropist(or orthodontist who follows similar principles) would move the upper incisors forward and upwards and bring the mandible up to meet it at a class I occlusion, and expand the maxilla/mandible so that the tongue can fit in the palate and the molars can fully erupt.

Another option other than orthotropics/orthodontics/mewing is a palate expander. It would help you gain lateral space to get your tongue out from between your teeth. And that could, if you fix your tongue posture and teeth close together, etc, allow your molars to fully erupt. Also, instead of the palate expander, devices like the DNA and ALF would help you with your lateral space and deep bite as well.

Hope that made sense and gave you some guidance on the cause/treatment, please let me know if you have any questions - and do seek other opinions and explanations and do your own research too. I'm not sponsoring any treatment, just spreading information.

Posted : 23/10/2019 11:33 pm
Active Member


Hey, I think what you said makes sense. My tongue is bigger in surface area than my families, so that might explain the lack of lateral space.

And, also, I am getting treatment to fix it. Its invisalign, and what suprised me is it moves the incisors on top up and forward a bit and the bottoms once to meet it, just like you said.

My only thing is, my 2nd molars do not move, up or down, and they do not even touch. I cannot maintain good resting occlusion as my jaw tends to loose stability as they do not even touch because my molars below have not erupted.

Would tongue posture encourage my lower arch to widen? And potentially aid in the eruption of these teeth so that I get closer to normal development. I did not get proper answers and, I need to know because if yes, that would mean ditching my retainers (I am halfway through treatment).

Posted : 24/10/2019 12:12 am
Eminent Member


You don’t really need the lower arch to expand to get your lower molars to erupt...they are intruded because you tongue hangs out between the upper and lower arches. So, if the upper arch expands to a point where the tongue can fit in the upper palate, the lower molars will erupt even without much increase in expansion of the lower arch. The lower arch fits the upper arch, so once you expand the upper arch the lower arch will slowly expand to meet it(chewing gum/food for 1 hour or so a day helps with this).

So, your real question should be how to expand the upper arch, I think. Mewing can help, but I’m not going to advise you on removing retainers, etc due to liability issues. Do your research please. I know it depends on your starting point in IMW. Progress and Greensmoothies have had success expanding around 10 mm starting from intermolar widths lower than yours, just through mewing. But if you don’t fix tongue posture properly and remove your retainer, it could lead to crowding/relapse. So again, please do your research and come to a knowledgeable decision. And don’t worry too much, it can erupt at any age, so time is not an issue.

Posted : 24/10/2019 12:45 am