Excessive teeth grinding or jaw clenching is never pleasant or convenient for bruxers, so does it make a difference when it happens? It actually might, because research suggests they may have different causes, symptoms and management approaches.
The two main types of bruxism are sleep bruxism and awake bruxism.
Experts consider them to be 2 separate conditions with different causes, and unfortunately it is possible to experience both at the same time. Bruxism behaviors like jaw clenching during the day can persist into sleep – called a carryover effect – so awake bruxism can contribute to sleep bruxism. But the carryover effect has a positive side as well: studies have shown that reducing bruxism activities during the day can help reduce how much you grind in your sleep [Sato et al. 2012].
Awake bruxism
As the name suggests, this type of bruxism occurs when you’re awake. It’s almost always characterized by teeth clenching or bracing/thrusting of the jaws (where you lock your jaw muscles in a fixed position, sometimes without tooth contact). Because it tends to be silent, it can go unnoticed for a while and make it harder for us to identify when we brux! Situations like deep concentration, high levels of physical exertion or feeling anxious can be common triggers of awake bruxism. Population studies estimate that 20-30% of us do it. One of the common symptoms is headaches / migraines, pain in the jaw or facial or neck muscles that tend to get worse throughout the day.
Sleep bruxism
Sticking with simple terms (which we love) this is teeth grinding or jaw clenching while you sleep. If you sleep in the same bed as someone else, they may even tell you they’ve woken up to the sounds of unsettling grinding, crunching or tapping sounds. If you notice that symptoms of headaches, jaw, ear or neck pain tend to be worse in the morning, you’re likely a sleep bruxer.
Sleep bruxism is more complex in terms of causes, but research suggests that it is multifactorial in nature, and that stress is a far less significant factor than it is in awake bruxism [Manfredini & Lobbezoo, 2009]. It used to be thought that it was caused by how your teeth fit together, but studies found similar rate of bruxism in people with and without perfect bite, and that bruxism can’t be fixed by changing your bite. Recent theories suggest that the brain’s central and autonomic nervous systems play a more dominant role, which explain the link between sleep-related microarousals, neurochemicals, genetics, and breathing disorders with bruxism behaviors [Yap & Chua, 2016].
Besides sleep and awake bruxism, there’s also four distinct jaw movements in bruxism – teeth grinding, teeth clenching (gritting), thrusting (jaw protrusion), and bracing (jaw muscle contraction without tooth contact).
Teeth grinders seem to have more dental issues like teeth attrition, chipped teeth or fillings and broken implants. Teeth clenchers tend to report more pain symptoms like jaw or facial pain, as well as migraine-like headaches.
The last difference we currently identify in bruxism is between primary (idiopathic) and secondary cases. Primary bruxers don’t have any clear cause for their teeth grinding or jaw clenching behaviors, and they’re not associated with any psychological or medical conditions. Secondary bruxers have an underlying condition that contributes to their teeth grinding or jaw clenching behaviors – examples include restless leg syndrome, sleep apnea, mandibular myoclonus, rapid eye movement disorders, autism spectrum disorder and primary or secondary dystonia. Alternatively, the behaviors can be attributed to drug use/withdrawal or with splint or dental restoration.
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References
Sato M, Iizuka T, Watanabe A, Iwase N, Otsuka H, Terada N, Fujisawa M. Electromyogram biofeedback training for daytime clenching and its effect on sleep bruxism. Journal of Oral Rehabilitation. 2015 Feb;42(2):83-9.
Manfredini D, Lobbezoo F. Role of psychosocial factors in the etiology of bruxism. J Orofac pain. 2009 Apr 1;23(2):153-66.
Yap AU, Chua AP. Sleep bruxism: Current knowledge and contemporary management. Journal of conservative dentistry: JCD. 2016 Sep;19(5):383.
