The medical term for teeth grinding. Usually during sleep and sometimes associated with stress, anger, or frustration. According to Wikipedia, symptoms associated with bruxism include "hypersensitive teeth, aching jaw muscles, headaches, tooth wear, damage to ... crowns and fillings, and damage to teeth." Like most medical jargon, adopted from Latin, in turn from Greek for gnashing the teeth, which I'm seeing cited as brykein/brukein or brychein/bruchein -- anyone know whether the original really has a kappa or chi?
There's two types of bruxism: men tend to grind, and hurt their teeth, while women tend to clench, and get headaches.