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Effect of chewing on the mandible  

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sinned
Estimable Member

I think you guys will find this pretty interesting, a neolithic mandible vs a paleolithic from a similar angle.

Noticeably, the arch of the paleolithic skull is wider and doesn't have crowding, however, I think this comes from correct tongue posture. You can also notice how the bottom skull is thicker while the top one is thinner, this seems to me to be the result of chewing. What I think basically occurs as a result of chewing is that the jaw gets "thicker" and as a whole bigger, it doesn't necessarily get wider, the width is a result from increased thickness. Of course, this is all speculative and nothing conclusive, not sure if this process also occurs in older people but it could possibly. 

https://www.sciencedaily.com/releases/2019/05/190531100544.htm

This study suggests there is some sort of mechanism for jaw bone remodeling as a result of masticatory forces.

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Posted : 02/07/2019 8:25 pm
Freddie liked
printfactory
Eminent Member

Very interesting post. I looked into the study and as far as I can see they used 3-14 week old mice. I wonder how well those results translate to adult mice  (3months+ of age) and humans.

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Posted : 28/07/2019 1:55 pm
sinned
Estimable Member

@printfactory

Me too, I assume something similar would happen in humans, even adult humans. When people lose all their teeth extreme bone loss occurs.

Related image

Image result for mandible with no teeth

If bone loss occurs after you lose your teeth and therefore the ability to chew and stimulate the jaw bone, I think the same probably happens in reverse.

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Posted : 28/07/2019 2:23 pm
Pame
 Pame
Trusted Member
Posted by: @sinned

@printfactory

Me too, I assume something similar would happen in humans, even adult humans. When people lose all their teeth extreme bone loss occurs.

Related image

Image result for mandible with no teeth

If bone loss occurs after you lose your teeth and therefore the ability to chew and stimulate the jaw bone, I think the same probably happens in reverse.

@sinned Precisely what changes occur when all teeth are lost? Looks like the chin tilts upward. Do these changes really occur solely due to the inability to chew? Its a quite characteristic look often seen in elderly people who lose all their teeth. I've never seen anything similar in people who barely chew.

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Posted : 28/07/2019 3:16 pm
sinned
Estimable Member

@pame

When you lose all your teeth your "bite" changes. I think this attributes to the chin tilting upwards. You're literally losing like an inch or so of tooth vertically speaking if that makes sense. So the mandible remodels upwards. In addition, the front teeth are longer vertically while the molars are shorter, this also could attribute to the chin tilting upwards.

https://www.pacificoralsurgeon.com/jaw-bone-health/

"Jaw bone health can be affected by dental health and structure such that tooth loss and the conditions which cause it are often contributing factors to jawbone deterioration or loss. Jawbone tissue, like any other bone tissue, requires use to be in good health. The teeth create a stimulus for the jawbone through biting and chewing. When the alveolar bone (jawbone), which anchors the teeth, is unstimulated, it begins to resorb, or break down. This deterioration of jawbone can cause problems with not only appearance, but overall health."

The teeth seem critical in creating stimulation for the jaw bone and maintaining jaw bone health. This is evident as even dentures can't prevent the deterioration of the jaw bone if you have no teeth. The only way to prevent it would be to get implants.

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Posted : 28/07/2019 4:41 pm
GoTTi liked
printfactory
Eminent Member

I have looked into it a bit more. The novel thing about the study @sinned linked was apparently their use of a computer model to predict how exactly the bone growth happens. There were studies about masticatory forces influencing bone growth 30+ years ago ( http://www.aofm.com.br/Files/Other/Articles/Masticatory%20muscle%20influence%20on%20craniofacial%20growth.pdf see here, and in the references). I have never heard anything about the importance of chewing from anyone (TV, school, orthodontists, dentists) while growing up.

I also found out that bones can increase in width through appositional growth which slows down with aging but never ceases completely.  ( http://library.open.oregonstate.edu/aandp/chapter/6-4-bone-formation-and-development/ )

It seems like mechanical loading triggers appositional bone growth (see here page 24 https://books.google.de/books?id=DNmNDwAAQBAJ&pg=PA24&lpg=PA24&dq=appositional+growth+exercise&source=bl&ots=r3VRqOAPJN&sig=ACfU3U3PKfdSTqf7CiRs88JpB2ZeQ2t8aQ&hl=en&sa=X&ved=2ahUKEwjew-ikptzjAhVPUlAKHUiTAJwQ6AEwDXoECAgQAQ#v=onepage&q=appositional%20growth%20exercise&f=false )

Another example would be tennis players having bigger bones in their hitting arm.

 

So it should be possible to add width to the mandible through appositional bone growth. However I don´t know how big the effect is.

 

 

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Posted : 30/07/2019 5:20 am
Shell liked
EddieMoney
Reputable Member

Why do some old people lose their teeth?

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Posted : 30/07/2019 8:17 am
sinned
Estimable Member

@eddiemoney

I think primarily diet, although brushing the teeth can offset the effect of diet on the teeth. Specifically gum disease and tooth decay. If you get resorption of the tooth as well as gum recession your teeth get loose. If decay of the teeth/gums is bad enough dentists will just remove the teeth since there's basically no way to recover them and you're at risk for infection and other problems. Basically there's a point of no return when it's just better to remove the teeth than to keep them. It's also possible that your teeth get so bad they fall out themselves.

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Posted : 30/07/2019 8:03 pm
Pame liked
sinned
Estimable Member

@printfactory

From your first link I find this especially interesting

"Thus, changes in bone apposition were observed not only in
the vicinity of the insertion of the elevator muscles but
also in areas where increased bone apposition reinforces
the bone so that it is able to withstand higher bending
forces in animals fed a hard diet (36, 45)."

If I understand correctly, there's a muscle effect as well as a mechanical force effect, by that I mean that the muscle itself has an effect on the bone, for example the chewing muscles can decrease the gonial angle. But there's also the factor of the forces produced by the chewing muscles, the forces produced by chewing affect the jaw bone primarily but also the whole skull as well.  This could explain why people who clench get headaches. It also explains why hunter gatherer skulls look so robust compared to modern individuals who in comparison look more neotenous. The forces from chewing for years and years might have some sort of effect on the robustness of a skull.

Image result for forces from chewing compared humans and apres

Here's an interesting image showing the bite force apes and humans and the stress placed on the skull

https://royalsocietypublishing.org/doi/10.1098/rspb.2010.0509

 

edit: I think the quote is just referring to the fact that bone deposition/appositional growth doesn't just occur on the muscle insertion itself but also the remaining jaw bone from the forces that occur from chewing. This makes me curious however if there is an effect on the bone when the muscle is at rest, does an increase in muscle thickness/strength/size place more stress on the bone? Or is it purely through the forces produced by said muscle that the bone remodels.

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Posted : 30/07/2019 8:25 pm
GoTTi liked
Pame
 Pame
Trusted Member
Posted by: @sinned

This makes me curious however if there is an effect on the bone when the muscle is at rest, does an increase in muscle thickness/strength/size place more stress on the bone? Or is it purely through the forces produced by said muscle that the bone remodels.

Its definitely an interesting question. Mike Mew talks about what he calls the "chewing effect", and says its a key element in ensuring a well developed face. Mew does not know though if the chewing effect is about placing stress on the jaw bone through chewing, or about having high bite strength or good muscle tone. I've seen studies showing a correlation between masseter thickness and brachyfacial patterns, as well as a correlation between high bite strength and transverse craniofacial morphology. There was also a recent study showcasing that increased stress placed on the jaw bone through mastication produces skeletal remodeling in adult age.

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Posted : 02/08/2019 4:01 pm
GoTTi liked
GoTTi
Trusted Member
Posted by: @eddiemoney

Why do some old people lose their teeth?

Acidosis.... When the body has faulty calcium intake or absorption, it'll strip the calcium from it's reserves. Teeth are considered a reserve for calcium etc.

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Posted : 02/08/2019 4:39 pm
GoTTi
Trusted Member
Posted by: @pame
Posted by: @sinned

This makes me curious however if there is an effect on the bone when the muscle is at rest, does an increase in muscle thickness/strength/size place more stress on the bone? Or is it purely through the forces produced by said muscle that the bone remodels.

Its definitely an interesting question. Mike Mew talks about what he calls the "chewing effect", and says its a key element in ensuring a well developed face. Mew does not know though if the chewing effect is about placing stress on the jaw bone through chewing, or about having high bite strength or good muscle tone. I've seen studies showing a correlation between masseter thickness and brachyfacial patterns, as well as a correlation between high bite strength and transverse craniofacial morphology. There was also a recent study showcasing that increased stress placed on the jaw bone through mastication produces skeletal remodeling in adult age.

so, theoretically speaking, if chewing has this effect on the jawbone, wouldn't other areas of the face be impacted the same way via something like facial yoga, or facial exercises (like the ones found here www.shapeyourface.com) or even (hypothetically speaking of course) some sort of ultrasound/frequency device that can simulate muscle growth?

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Posted : 02/08/2019 4:40 pm
sinned
Estimable Member

@gotti

Yes and no. Yes that the muscles of the face impact the bone, but no not in the same way as the jaw. Difference being the jaw muscle produces way more force, however facial muscles still have some sort of effect, evidenced by stroke victims who lose control of their facial muscles and/or get atrophy. Also I've heard of some ultrasound/frequency device that affects the bone in some sort of way, that's as far as I can remember though.

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Posted : 02/08/2019 6:29 pm
GoTTi
Trusted Member
Posted by: @sinned

@gotti

Yes and no. Yes that the muscles of the face impact the bone, but no not in the same way as the jaw. Difference being the jaw muscle produces way more force, however facial muscles still have some sort of effect, evidenced by stroke victims who lose control of their facial muscles and/or get atrophy. Also I've heard of some ultrasound/frequency device that affects the bone in some sort of way, that's as far as I can remember though.

The ultrasound device you're referring to may be something called "Lipus" and it's based on certain frequencies that can penetrate through many layers and get into bone to speed up bone remodeling. It's basically the same technology that has been used to regrow body parts of all sots on animals and a piece of a human finger tip. It is theorized to eventually heklp with the regrowth of limbs in the future. Very interesting stuff.

As far as atrophy goes, ah ok, that makes sense. Use it or lose it. I'm guessing their facial changes are so dramatic because they lose complete function of the muscle. Not partial, but 100% of it. So, theoretically speaking, if this issue is corrected and muscle function is restored, one can experience a relapse and correct their asymmetry since they are once again utilizing their muscles?

Edit: IIs there any evidence suggesting that facial muscles being worked out don't induce bone deposition by exercising them through more invasive techniques in  comparison to general utilization, like facial yoga for example? I can see how atrophy or inflammation can induce structural changes, I can also see how bad posture can induce some change as well. If you body is out of alignment, your body will compensate so that your 5 senses and your genitilia are safe and functioning optimally. Upon postural correction, your neck will be held in a more optimal position and only then can the muscles of the shoulder and neck stop pulling on your mandible making it recede, same with some of the rest of the bones on your face and head. Does this correlate with some of your research?

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Posted : 02/08/2019 7:28 pm
ilovemyself
New Member

@sinned

It's just an mm in the harmony 

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Posted : 03/08/2019 12:11 pm
ilovemyself
New Member

@sinned

It's just an mm in the harmony 

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Posted : 03/08/2019 12:11 pm