Sleep bruxism is very damaging to the teeth, jaws, muscles and TMJ. It is a significant cause of tension/migraine type headaches and tooth sensitivity. The following is a system by system summary of the effects of sleep bruxism.
Rhythmic movements such as chewing and bruxing are controlled by central pattern generators (CPG) within the brain. Chewing (and sleep bruxism) are driven by the hypoglossal nucleus, which is controlled by the dorsal medullary reticular column (DMRC) and the nucleus of the tractus solitaries (NTS). At some level, the sympathetic cardiac system is activated, as evidenced by the increase in heart rate with each sleep bruxism event. To date there is no consensus on the exact mechanism by which sleep bruxism occurs. (Central pattern generators in the nervous system also control waking, breathing and other autonomic cycling-type body functions).
Cracked fillings: the pressure of sleep bruxism can easily fracture fillings and/or shorten their lifespan requiring frequent replacement (Figure 1).
Cracked teeth are also common. These teeth are very sensitive to biting only hard foods as the crack opens and closes (Figure 2).
The roots of the teeth can actually crack requiring removal of the tooth (Figure 3).
Localized bone loss can occur due to side to side forces concentrated on one tooth (Figure 4).
Painful abfraction lesions (notches) can occur at the gumline on upper and lower teeth (Figure 5).
Hypersensitivity to hot and cold foods is a hallmark sign of sleep bruxism (Figure 6).
The Jaw Bones (Mandible and Maxilla):
In this view the stylomandibular ligament has calcified. This is termed Eagle’s Syndrome. If it fuses completely there can be restrictions in opening the jaws and in turning the neck (Figure 7).
There is a bend in the mandible termed “antigonial notching” (Figure 7). This is due to excessive pressure of the masseter muscle during sleep bruxism events.
In this view (Figure 8), the coronoid process (the Temporalis muscle attaches here) is stretched longer (higher, marked with the orange dotted line. The yellow dot shows the correct height) by excessive muscle pull during sleep bruxism events. If stretched too far, this restricts side to side mobility of the lower jaw as the coronoid process bumps into the cheekbone.
When excessive torquing pressure is placed on bone, the bone will adapt to prevent injury (breakage). In the case of the jaws, these are termed torus (singular) and tori (plural). Figure 9 demonstrates moderate sized tori and where they are most commonly seen in the lower jaw. This location is not by chance. This region is one of the higher risk areas for fracturing.
Another bone adaptation seen in sleep bruxism are exostoses or bone outgrowths on the jaw bones. Figures 10 and 11 demonstrate this on the lower and upper jaws. If a sufferer of sleep bruxism requires dentures, these bone outgrowths must all be removed before the dentures can be made.
The TMJ (Jaw Joints):
Sleep bruxism causes considerable pressure on the TMJ. This causes pain in the TMJ, clicking and closed locking in the morning. Over time, if left untreated, the TMJ can break down irreversibly. Figure 12 below demonstrates normal TMJ movement. The disk (yellow in animation) remains between the bones the entire opening and closing cycle.
In the early stages, the disk starts to slip out of alignment when biting, but “clicks” into place when the jaw starts to open and remains there for most of the opening and closing cycle (Figure 13).
When biting, the disk is dislocated forward. With sleep bruxism, the teeth are together most of the night resulting in progression of damage to the TMJ over time.
The last scenario is where the disk tears free and never resets into position. This is termed a closed lock. The American Academy of Sleep Medicine list closed locks on waking, resolving as the day goes on as a common sign of sleep bruxism (Figure 14). Closed locking of the TMJ is a very common morning occurrence which usually resolves within an hour or two. Over time, this can permanently lock, requiring surgical intervention to stabilize the joint(s).
TMJ problems are very common in those suffering from sleep bruxism. Conventional TMJ therapies often overlook this condition and it goes untreated.
The two main muscles involved in sleep bruxism are the temporalis (Figure 15), located on the side of the head and temple region, and the masseter, which is the main chewing muscle in your cheek. These muscles are seriously overworked in sleep bruxism and can become damaged or diseased over time.
Sleep bruxism can cause these muscles to fatigue very easily. Chewing meat or harder foods can result in pain due to this. Over time, areas of these muscles can become diseased and form myofascial trigger points. These are areas where the muscle tightens and remains tightened. The trigger points are painful to palpate and have the characteristic of referring pain to adjacent regions, very predictably.
As can be seen in Figure 16, the temporalis pain referral pattern for the front fibers is into the temple and upper incisor region. Headaches in the temples on waking, or later in the day, are a hallmark symptom of sleep bruxism and this is one of the causes.
Figure 16: Temporalis Muscle Trigger Point Referrals
In Figure 17, the masseter muscle pain referral patterns include both upper and lower back teeth, over the eye and temples as a tension headache.The masseter muscle also can refer pain to the temple regions and is another common cause of morning headaches. These headaches are reported by patients as moderate to severe in nature and can occur in waking, or later in the day. Waking to a severe headache is not a pleasant way to start the day and depression can also occur in susceptible people.
Figure 17: Masseter Muscle Trigger Point Referrals
The muscles under the jaw also are involved in sleep bruxism. They are activated just as the masseter and temporalis and contract with considerable opposing force, attempting to open the jaw. As they are much smaller, they cannot and often develop trigger points. Figure 18 shows the trigger point referral pattern for the digastric muscles (anterior and posterior):
Figure 18: Digastric Trigger Point Referrals
Muscle Hypertrophy (over-development)
If sleep bruxism is present in the severe form for an extended time, the jaw muscles can enlarge, like a bodybuilders.
This altesr the appearance of the person (Figure 19). This also increases the strength of the muscle resulting in even greater damage to the teeth during sleep bruxism events.
The only effective treatment for reducing this muscle hypertrophy is with the use of Botox injections, which has been shown to reduce excessive muscle mass over a few treatments.
Every sleep bruxism event results in a cascade of events including an increase in blood pressure and heart rate. A normal sleeping heart rate is generally much less than 90 beats per minute (bpm). With sleep bruxism, the heart rate can climb as high as 140-150 bpm, placing stress upon the heart. This is due to activation of the trigeminal cardiac reflex (TCR) at the level of the Gasserion (trigeminal) ganglion of the brain. This stimulates the vagus dorsal motor nucleus which results in an increase in heart rate, blood pressure and rate of respiration.
The tracing below (Figure 20) demonstrates a typical sleep bruxism event and below the effect on heart rate (increasing from 70 bpm to 96 bpm. The horizontal dotted lines in the tracing indicate the normal range of jaw movement during sleep. Sleep bruxism far exceeds this level.
Quality of Sleep:
Sleep bruxism results in hundreds of sleep arousals each night, prevented deep restorative sleep. The Epworth Sleepiness Scale (ESS) is used internationally to screen for tiredness during the daytime. Less than ideal sleep has been associated with many different diseases as well as in increasing the risk of a motor vehicle accident or industrial accident. It impairs memory formation and learning and can cause depression in some.
With sleep bruxism, ESS scores of 4-9 are common. Sleep apnea starts at 10+. Sleep bruxism can cause daytime tiredness almost as bad as mild sleep apnea and can result in decreased productivity, poor memory consolidation, and poor quality sleep.
Research tends to focus on the disease and rarely on the family members. With sleep bruxism, the sound of grinding teeth has been shown to be very disturbing to most people. This can disturb the sleep of the bed partner or even family members in adjacent rooms!
Considering everything discussed here, it is obvious that sleep bruxism can have a great effect on quality of life. Treatment of sleep bruxism with the only FDA cleared treatment, the Luco Hybrid OSA Appliance, can dramatically improve quality of life for those suffering from this disease, as well as their family members. It is currently available in Canada and the USA. Contact your dentist today if you feel you suffer from this common and serious disorder.