It's A Mouthful

Remember when I said that I was "perfectly okay being a freak in many other regards"? Today, I introduce you to one of the ways in which I'm a freak, and the physical manifestation of it.

I suffer from bruxism, and as a result I have exostotic mandibular tori.

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Alright, that's a lot of medical terminology, and today's fun fact is (like the one about the popliteal fossa) about telling you the proper names for things you didn't know the names of. In this particular case, you may not even know that they exist. So let's break this down into simpler, smaller, bite-sized nuggets, shall we?

Bruxism is grinding your teeth or clenching your jaws, either while awake or asleep, and I've had a great deal of difficulty in finding stats for its prevalence. It's cited as one of the most common dental problems in the developed world, and it's also listed as one of the most common sleep disorders. Either way, about 33% of children do it regularly but most grow out of it. Depending on the study, between 5% and 85% of people are bruxers (yes, that's the proper word for someone with bruxism), while the majority report somewhere in the 10% range are chronic bruxers. About 5% of the population suffers from bruxism to a degree that they need treatment for their symptoms (usually headaches, jaw pain or tooth damage). I personally am not a tooth grinder, but a jaw clencher, both while awake and in my sleep.

Exostotic is the adjective (modifies a noun, if you forget your grammatical definitions) form of exostosis, which itself means bony outgrowth (ex = out, ostosis = bone growth). This is as opposed to an osteoma, which is a benign bone tumor.

Which brings us to the strangest of the odd medical terms I threw around up there: Mandibular tori. That's a plural of mandibular torus, in case you're wondering. Mandibular is, obviously, associated with the mandible, or jawbone. A torus, if you remember back to your geometry lessons, is a doughnut shape. In anatomy it refers to a rounded ridge, because it looks like the edge of a torus. Anatomically, it doesn't need to be a complete torus, just shaped like part of a torus. A mandibular torus is a bony outgrowth on the curved inner part of your mandible.

An exostotic mandibular torus is a bony outgrowth caused by damage to the jaw, usually through stressing the bone through prolonged pressure. The kind of pressure that one exerts when they clench their jaws. Exostotic mandibular tori usually form in roughly symmetrical growths on both sides of the mandible, while mandibular tori formed by osteomata rarely form symmetrically.

Normally, at this point, I'd throw a picture at you, but pictures of the insides of someone's mouth, even when it's perfect, aren't super pleasant. And pictures of a perfect mouth are pretty much unknown on the internet. All you get are the freak cases. So I will, instead, give you a CT scan, which aren't nearly as gross. Feel free to search for mandibular tori on your own if you want to look at the inside of freak mouths.

Those eight lumps on the interior
of the jaw? Signs of a bruxer.

Not everyone who grinds or clenches their teeth get mandibular tori, and not everyone with mandibular tori clench or grind their teeth, but there is a strong connection between the two. There seems to be some sort of genetic predisposition, but it's unclear whether the genetic element plays more into the likelihood of being a bruxer or of forming exostoses. What is clear is that roughly 10% of the North American population has them, with no significant variance between whites or blacks, and only a minor difference between men (more likely) and women. Worldwide the prevalence varies between 5% and 40%, with the higher numbers coming from Asian and Inuit populations.

The reason that it's not considered strictly a genetic condition despite the large racial disparities is this: The can grow and shrink over time. For some people something as simple as wearing a mouthguard while sleeping is enough to make the tori slowly disappear due to reduced stress on the jaw. Clearly it's sometimes caused by environmental factors, but the high rates amongst the Inuit point towards a genetic predisposition as well. Since mandibular tori are almost always totally benign and rarely cause problems until you need dentures (at which point they pretty much just get in the way) there's not a great deal of research on what causes them. Bigger fish to fry, as it were.

They can be surgically removed but, like the appendix, there's not a whole lot of reason to do it as a preventative measure. Particularly since they can grow back. The most common problem with them (other than the denture thing) is cutting the skin covering them on sharp food like chips. Sometimes they can become so large that they interfere with swallowing and moving the tongue though, in which case medical attention is probably a good idea.

Exostotic mandibular tori: A mouthful of words for a mouthful of bone.

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Sources:
Mandibular tori CT scan image taken from Radiopaedia.org
Studio Dentaire article on bruxism
Bio-medical.com article on bruxism
Soft Dental dental services
Anesthesia-Analgesia.org article on mandibular tori - PDF
Wikipedia entries on bruxism and mandibular tori
Dictionary.com pages for bruxism, exostosis, torus and osteoma