29 ms·

"The arrangement of the muscle fibers, she says, suggests that this layer is involved in the stabilization of the lower jaw. It also appears to be the only part

"The arrangement of the muscle fibers, she says, suggests that this layer is involved in the stabilization of the lower jaw. It also appears to be the only part of the masseter that can pull the lower jaw backwards – that is, toward the ear."

trelane 5y ago
Seems a surprise that this has taken so long to be discovered, as every motion seems to require two muscles--one to pull and the other to relax/lengthen.
- yololol 5y ago
  To me it seems a surprise that this has taken so long to be discovered in general. I thought we would know all muscles by now.
  - Retric 5y ago
    It’s been known about for at least 25 years, but there was some debate about the specifics. Thus they “described this layer in detail for the first time.”
    - rbanffy 5y ago
      It spent a good couple million years literally under our noses.
- PaulHoule 5y ago
  It astonishes me how little help people can get for the very common TMD so I am not surprised to find anything is misunderstood about the functional anatomy of the jaw.
  - AstroDogCatcher 5y ago
    Yes. First experienced TMJ pain as a teenager and almost overdosed on painkillers while trying to get rid of it at 3AM. Still recurrs about 2-3 times per year, but I've now learned to feel it coming on much earlier and start loading up on codiene in advance.
    - jacobolus 5y ago
      For other folks not familiar with these abbreviations, https://en.wikipedia.org/wiki/Temporomandibular_joint_dysfunction https://en.wikipedia.org/wiki/Temporomandibular_joint_dysfun...
    - mkl95 5y ago
      I have been getting it 10+ times a year since my early 20s. Whenever it happens it's as terrifying as the very first time.
      - PaulHoule 5y ago
        I had it a long time and was not sure the pain was localized in the jaw (was it the neck, shoulders, back?) or even the extent to which there was a physical lesion or it was how my brain was interpreting things. My dentist told me I was grinding my teeth and prescribed a bite guard and within two weeks the pain got better but became very definitely focalized in the jaw and I noticed ‘popping’ as a symptom. It has been about 1.5 years since the diagnosis. last summer I went through a phase of throwing a lot of random food into a pot and hitting it with an immersion blender, getting shakes from Burger King whenever I felt like it, etc. I lost almost 20 kg. I have been eating more normally since, it doesn’t bother me very often.
        xhevahir 5y ago
        What sort of bite guard did you use? I clench my teeth like there's no tomorrow and I've discovered over the years that any bite guard that doesn't completely cover every tooth (on either the lower or upper arch) will eventually result in a supra-eruption of the exposed tooth, with drastic consequences for my bite.
  - azinman2 5y ago
    I thought Botox helped?
    - PaulHoule 5y ago
      I'm sure it does but I am sure sham injections help too.
    - amelius 5y ago
      Yes. Found this personal blog: https://www.byrdie.com/botox-for-teeth-grinding https://www.byrdie.com/botox-for-teeth-grinding and scientific review paper: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5634354/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5634354/
  - cjbgkagh 5y ago
    AFAIK it’s most likely a connective tissue disorder as opposed to muscular. For this there is also little help and rarely diagnosed. But at least may help find answers for comorbidities that are often considered unrelated.
  - celdon25 5y ago
    I've suffered since the age of 21, but the attacks are less frequent these days (I'm 35). I do not take any painkillers for it, even OTC. I have tried 6 or 7 "professionally-made" mouth guards, some of which cost thousands. None of them helped and would actually make it harder to sleep at night. I instead deal with it by using heat, massage (full body is key), exercise, and nutrition. For the record, I am also blown away by how incompetent the medical and dental professions are at treating this. Tap your teeth on a piece of paper? Puh-leeze, that does nothing when your joints or muscles shift at different times of the day, and maybe 1 in 5 dentists actually know how to properly account for that based on my experience dealing with them over the years. And swear to god, if I hear another licensed and credentialed dentist describe my joint hypermobility as "your jaw is weird", I'm going to shit a brick.
  - novaleaf 5y ago
    I had severe pain in this exact location. When diagnosing, I was suggested to get my wisdom teeth removed. When they were removed the oral surgeon suggested I wear teeth guards when sleeping, because I had severe wear on my molars. So I'm not sure which of those (or both?) were the cause, but since removing my wisdom teeth I have worn a teeth guard every night, and I don't have that pain anymore.
pryce 5y ago
My set of Netter's Anatomy flashcards from medical school a decade ago describe the functions of the deep fibers of masseter (the 2nd layer of the masseter muscle) as 'retracting' the mandible. Interestingly the cards also say -here I interpret as regarding the superficial layer of masseter - that "some of its fibers may protrude the mandible" (which makes sense if you look at the diagram). What is lost in translation or reinterpretation in the quote you've posted is that retracting the mandible is either the function of the deep layer of masseter or instead the function of this newly discovered third 'coronoid' layer (or quite possibly, both); it is not as though anatomists thought 'how the jaw retracts' to be unanswered before today, but rather it seems they have been using an incorrect or perhaps incomplete picture. Interestingly I can see the stark difference in depiction between Netter's diagram illustrating deep masseter [1] and this other one.[2] I also note the description from Netters, which states that part of Masseter inserts on "the lateral surface of the coronoid process", describes pretty well the muscle being announced in this paper, as per their photographs. [1] https://ranzcrpart1.fandom.com/wiki/Temporal_fossa:Masseter_muscle?file=Muscles-of-mastication-lateral-view.jpg https://ranzcrpart1.fandom.com/wiki/Temporal_fossa:Masseter_... [2] https://www.medspine.es/wp-content/uploads/2017/02/Sin-t%C3%ADtulo-2.png https://www.medspine.es/wp-content/uploads/2017/02/Sin-t%C3%...
xapata 5y ago
That statement leaves out the other muscles that pull the lower jaw backwards. It's making the discovery sound more sensational than it is.

trelane 5y ago

Seems a surprise that this has taken so long to be discovered, as every motion seems to require two muscles--one to pull and the other to relax/lengthen.

yololol 5y ago
To me it seems a surprise that this has taken so long to be discovered in general. I thought we would know all muscles by now.
- Retric 5y ago
  It’s been known about for at least 25 years, but there was some debate about the specifics. Thus they “described this layer in detail for the first time.”
  - rbanffy 5y ago
    It spent a good couple million years literally under our noses.
PaulHoule 5y ago
It astonishes me how little help people can get for the very common TMD so I am not surprised to find anything is misunderstood about the functional anatomy of the jaw.
- AstroDogCatcher 5y ago
  Yes. First experienced TMJ pain as a teenager and almost overdosed on painkillers while trying to get rid of it at 3AM. Still recurrs about 2-3 times per year, but I've now learned to feel it coming on much earlier and start loading up on codiene in advance.
  - jacobolus 5y ago
    For other folks not familiar with these abbreviations, https://en.wikipedia.org/wiki/Temporomandibular_joint_dysfunction https://en.wikipedia.org/wiki/Temporomandibular_joint_dysfun...
  - mkl95 5y ago
    I have been getting it 10+ times a year since my early 20s. Whenever it happens it's as terrifying as the very first time.
    - PaulHoule 5y ago
      I had it a long time and was not sure the pain was localized in the jaw (was it the neck, shoulders, back?) or even the extent to which there was a physical lesion or it was how my brain was interpreting things. My dentist told me I was grinding my teeth and prescribed a bite guard and within two weeks the pain got better but became very definitely focalized in the jaw and I noticed ‘popping’ as a symptom. It has been about 1.5 years since the diagnosis. last summer I went through a phase of throwing a lot of random food into a pot and hitting it with an immersion blender, getting shakes from Burger King whenever I felt like it, etc. I lost almost 20 kg. I have been eating more normally since, it doesn’t bother me very often.
      - xhevahir 5y ago
        What sort of bite guard did you use? I clench my teeth like there's no tomorrow and I've discovered over the years that any bite guard that doesn't completely cover every tooth (on either the lower or upper arch) will eventually result in a supra-eruption of the exposed tooth, with drastic consequences for my bite.
- azinman2 5y ago
  I thought Botox helped?
  - PaulHoule 5y ago
    I'm sure it does but I am sure sham injections help too.
  - amelius 5y ago
    Yes. Found this personal blog: https://www.byrdie.com/botox-for-teeth-grinding https://www.byrdie.com/botox-for-teeth-grinding and scientific review paper: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5634354/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5634354/
- cjbgkagh 5y ago
  AFAIK it’s most likely a connective tissue disorder as opposed to muscular. For this there is also little help and rarely diagnosed. But at least may help find answers for comorbidities that are often considered unrelated.
- celdon25 5y ago
  I've suffered since the age of 21, but the attacks are less frequent these days (I'm 35). I do not take any painkillers for it, even OTC. I have tried 6 or 7 "professionally-made" mouth guards, some of which cost thousands. None of them helped and would actually make it harder to sleep at night. I instead deal with it by using heat, massage (full body is key), exercise, and nutrition. For the record, I am also blown away by how incompetent the medical and dental professions are at treating this. Tap your teeth on a piece of paper? Puh-leeze, that does nothing when your joints or muscles shift at different times of the day, and maybe 1 in 5 dentists actually know how to properly account for that based on my experience dealing with them over the years. And swear to god, if I hear another licensed and credentialed dentist describe my joint hypermobility as "your jaw is weird", I'm going to shit a brick.
- novaleaf 5y ago
  I had severe pain in this exact location. When diagnosing, I was suggested to get my wisdom teeth removed. When they were removed the oral surgeon suggested I wear teeth guards when sleeping, because I had severe wear on my molars. So I'm not sure which of those (or both?) were the cause, but since removing my wisdom teeth I have worn a teeth guard every night, and I don't have that pain anymore.

pryce 5y ago

My set of Netter's Anatomy flashcards from medical school a decade ago describe the functions of the deep fibers of masseter (the 2nd layer of the masseter muscle) as 'retracting' the mandible. Interestingly the cards also say -here I interpret as regarding the superficial layer of masseter - that "some of its fibers may protrude the mandible" (which makes sense if you look at the diagram). What is lost in translation or reinterpretation in the quote you've posted is that retracting the mandible is either the function of the deep layer of masseter or instead the function of this newly discovered third 'coronoid' layer (or quite possibly, both); it is not as though anatomists thought 'how the jaw retracts' to be unanswered before today, but rather it seems they have been using an incorrect or perhaps incomplete picture. Interestingly I can see the stark difference in depiction between Netter's diagram illustrating deep masseter [1] and this other one.[2] I also note the description from Netters, which states that part of Masseter inserts on "the lateral surface of the coronoid process", describes pretty well the muscle being announced in this paper, as per their photographs. [1] https://ranzcrpart1.fandom.com/wiki/Temporal_fossa:Masseter_muscle?file=Muscles-of-mastication-lateral-view.jpg https://ranzcrpart1.fandom.com/wiki/Temporal_fossa:Masseter_... [2] https://www.medspine.es/wp-content/uploads/2017/02/Sin-t%C3%ADtulo-2.png https://www.medspine.es/wp-content/uploads/2017/02/Sin-t%C3%...

xapata 5y ago

That statement leaves out the other muscles that pull the lower jaw backwards. It's making the discovery sound more sensational than it is.