The dental classification considers sleep bruxism as a parafunction in which the masticatory muscle activates involuntarily during sleep, resulting in an excessive clenching and grinding of teeth that can either exist independently of any other medical condition (primary sleep bruxism) or can be associated with another medical condition, psychiatric condition or sleep‐related disorder (secondary sleep bruxism).
It is generally believed that the presence of sleep bruxism alongside other sleep disorders is related to sleep fragmentation, micro-arousals from sleep and activation of the autonomic nervous system, although there is still debate about the precise pathophysiology. The prevalence of sleep bruxism is considered to be around 8–13% of the general population and the prevalence appears to be increased in people with OSA.12
The clenching and grinding action of bruxism can produce significant bite forces which, during sleep, are not suppressed by protective neuromuscular reflexes that operate when awake. This heavy loading of teeth, periodontium, temporomandibular joints (TMJ) and masticatory apparatus can lead to temporomandibular disorders, headaches, hypersensitive or painful teeth, implant and restoration failures and increased rates of periodontal disease progression. The abrasive action of grinding can also lead to tooth wear/fracture and sleep partner disturbance. Sleep bruxism can also therefore affect quality of life, cause anxiety and lead to relationship problems.
Known risk factors for sleep bruxism include presence of OSA, gastroesophageal reflux disease (GERD), alcohol use, loud snoring, caffeine intake, smoking, anxiety, stressful life circumstances, competitive personality and use of antidepressants or antipsychotics.
Sleep bruxism can be diagnosed in a number of ways:
Patients who brux (or their sleep partners) may be aware that they are grinding their teeth during sleep or may be aware of clenching or jaw stiffness/pain upon waking. Tooth surface loss can be a sign of ongoing bruxism but may be historical or related to other dietary or gastric factors. Similarly, painful masticatory muscles can be caused by bruxism, but a patient with a painful temporomandibular disorder (TMD) is not necessarily bruxing. Therefore, a diagnosis should not be made based on the above observations alone. Other relevant clinical factors may include masseteric hypertrophy, muscle tenderness on palpation, restoration or tooth fracture, tongue scalloping and ridging on the cheek mucosa.
EMG uses sensors attached to the skin over the masseter or temporalis to record the electrical activity of the muscles and nerve cells. This provides information about muscle activity and can reveal nerve dysfunction, muscle dysfunction or problems with nerve-to-muscle signal transmission.
This can detect the rhythmic masticatory muscle activity (RMMA) of sleep bruxism that is concomitant with a micro-arousal from sleep. Most events occur during stages N1 and N2 of NREM sleep although rarely events will occur in REM sleep (typically related to medication use or neurodevelopmental disorders).
For diagnosis of sleep bruxism, the AASM recommends considering patient report/awareness of sounds of tooth‐grinding during sleep, confirmed by a sleep partner and occurring in conjunction with:
In 2013 an international consensus recommended that self-reported events along with a clinical examination are sufficient for a probable diagnosis, but a concrete diagnosis would require PSG or EMG recording (with PSG being the gold standard, although this standard cannot be applied in most clinical settings due to cost and therefore this is most likely to be used in research).14
Sleep hygiene and lifestyle measures may include relaxation techniques, reducing caffeine or alcohol intake close to bedtime, improving ventilation and reducing noise in the bedroom.
Mandibular Advancement Devices (MADs) are used when sleep-disordered breathing is suspected or confirmed (i.e., when the bruxism is a comorbid condition to snoring and obstructive sleep apnea). These will both protect the teeth and reduce the occurrences of airway collapse that may be causing the bruxing.
Occlusal splints / night guard should be prescribed under the care of a dentist and, once in use by the patient, the device should be checked regularly for signs of damage caused by ongoing bruxing.
Sleep-disordered breathing (SDB) describe a group of disorders characterized by abnormalities of the respiratory pattern or ventilation during sleep.