Sleep-Related Bruxism’s Effect on the Autonomic Nervous System

The Trigeminal Cardiac Reflex (TCR)

The TCR is an autonomic cranial reflex (located in the brain) that was first discovered in humans in 1999. It manifests as a sudden onset of hemodynamic changes in blood pressure (MAPD) and heart rate (HR), breathing rate, and gastric motility (acid production in the stomach, GERD), which are autonomically regulated.

The TCR is actually made up of a  group of reflexes that affect the autonomic nervous system with the afferents (stimulation) occurring from direct stimulation of the trigeminal nerve (cranial nerve 5). The stimulation may be chemical, surgical or thermal.

Based upon where the trigeminal nerve is stimulated (externally at the eyes, face, teeth, and jaws) or internally (at the Gasserion ganglion, the trigeminal nucleus of the pons or the brain stem) determines if the effect will be sympathetic or parasympathetic.

Based upon the latest classification of the TCR, the following animations break down each component reflex of the TCR and lists the effects seen.

 

The Occulo-Cardiac Reflex: Parasympathetic

  • Simulation: Pressure on the eyeball, stimulation of the region around the eyes
  • Effect: bradycardia, apnea, hypotension, decreased cranial pressure, increased gastric motility

In the above animation, stimulation of the trigeminal nerve in the eye region (or by pressure directly on the eyeball) activates the TCR.

(Abbreviations Used: Tachycardia = increased heart rate, Bradycardia = slowing of heart rate, apnea = slowing or stoppage of breathing, Hyperpnea = increased rate of breathing, Hypotension = drop in blood pressure, Hypertension = increase in blood pressure, Gastric Motility = stomach acid production)

The Naso-Cardiac Reflex: Parasympathetic

  • Stimulation: the sides of the nose, nose region of the face, inside the nose
  • Effect: bradycardia, apnea, hypotension, decreased cranial pressure, increased gastric motility

In the above animation, stimulation of the trigeminal nerve in the nose region activates the TCR.

 

The Maxillo-Mandibular Reflex: Parasympathetic

  • Stimulation: The upper and lower lips and skin in the lower face
  • Effect: bradycardia, apnea, hypotension, decreased cranial pressure, increased gastric motility

In the above animation, stimulation of the trigeminal nerve in the upper lip and lower lip regions active the TCR.

 

The Bicuspid Cardiac Reflex (a subset of the maxillo-mandibular reflex): Parasympathetic

  • Simulation: the upper and lower 1st bicuspids by root canal therapy or pressure on the bicuspid teeth
  • Effect: bradycardia, apnea, hypotension, decreased cranial pressure, increased gastric motility

In the above animation, stimulation of the trigeminal nerve in the upper and lower 1st bicuspids activates the TCR.

 

The Gasserion Ganglion Reflex: Sympathetic

  • Stimulation: direct stimulation of the Gasserion Ganglion (this is where sleep-related bruxism and restless leg syndrome affect the TCR)
  • Effect: tachycardia, hyperpnea, hypertension, increased cranial pressure, increased gastric motility (seen as GERD).

In the above animation, the stimulation of the trigeminal nerve occurs at the Gasserion Ganglion activating the TCR.

 

The Central Reflex: Parasympathetic

  • Stimulation: at the trigeminal sensory nucleus in the brainstem
  • Effect: bradycardia, apnea, hypotension, decreased cranial pressure, increased gastric motility

The Brain Stem Reflex: Parasympathetic 

  • Stimulation: in the brainstem, after the trigeminal sensory nucleus
  • Effect: bradycardia, apnea, hypotension, decreased cranial pressure, increased gastric motility

In the above animation, the stimulation occurs in the reticular formation of the brainstem, activating the TCR.

Sleep-Related Bruxism and the TCR

As discussed, sleep-related bruxism affects the TCR at the level of the Gasserion Ganglion sympathetically. Studies have found that heart rate is the most significant measurement of TCR activation.

It is medically accepted that there must be a change of greater than 20% in heart rate before a diagnosis of TCR stimulation may be made. In sleep-related bruxism, there is a sympathetic increase in the range of 70-90% seen, indicating sleep-related bruxism is hyper-activating the TCR significantly.

Over time and repeated incidence of TCR activation, the kidneys are at risk of damage. The kidneys contain tiny, thin-walled blood vessels that may be damaged by spikes in blood pressure. This damage results in reduced kidney function, one of the most important being control of blood pressure. More sleep-related bruxism and the vicious cycle continues.

The sleep tracing demonstrates this effect in action. Heart rate increases from 49 to 90 beats per minute! This is a 41% increase occurring within seconds of the event. This supports the sudden sympathetic hemodynamic changes seen to exist with TCR activation at the Gasserion ganglion by sleep-related bruxism, which is the opposite the other six reflexes. It also greatly exceeds the medically accepted threshold of 20% change in heart rate.

In sleep-related bruxism, heart rate is hyper-stimulated with increases of 40-120% not uncommon.

 


 

The Sleep-Related Bruxism Cardiovascular Connection:

Rapid heart rate

There is a rapidly growing body of evidence that sleep-related bruxism is a risk factor for the development of the cardiovascular disease.

Catecholamines are naturally occurring molecules produced by the adrenal glands that are strongly associated with cardiovascular diseases. In sleep-related bruxism, urinary catecholamines have been shown to be elevated, implicating sleep-related bruxism as a potential case.

 


The significance of the Forward Bite of the Luco Hybrid OSA Appliance

The Luco Hybrid OSA Appliance (LHOA) features a patented forward bite (protected by US patent 9,545,332 B2) places the bite over the cuspid and first bicuspid. This has three significant effects:

1. Activation of the PMR reflex to limit bite force

By placing pressure on the cuspid, the periodontal masseter reflex (parasympathetic) is activated. It is similar to the masseter Inhibitory Reflex and unaffected by the HTR2A polymorphism.

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Activation of the PMR results in inhibition of the masseter muscle to contract, limiting the biting force to normal limits. This significantly reduces sleep-related bruxism events and associated signs and symptoms.

2. Peripheral activation of the TCR reflex is parasympathetic

Secondly, by placing pressure on the cuspid and first bicuspid, the Bicuspid Cardiac Reflex is activated, reducing heart rate and blood pressure to normal levels.  This reflex activates the TCR conventionally, by lower heart rate, breathing rate, blood pressure, etc.

By activation of the bicuspid cardiac reflex, the effects of stimulation of the Gasserion Ganglion reflex activation seen in sleep-related bruxism are not seen. One is stimulating the cardiovascular system and the other is suppressing it. The net result is one cancels the other out and no stimulation of the cardiovascular system is seen.

3. Even stress distribution of the bite force, protection of the TMJ

By placing the bite over the cuspid and 1st bicuspid, this provides a very even stress distribution of forces over bones making up the face and forehead.

 

 


The patented forward bite is by far the most significant effect that the Luco Hybrid OSA Appliance has, and is the most significant difference from other mandibular advancement appliances and single arch bruxism appliances. 

(protected by US patent 9,545,332 B2)

With the use of the Luco Hybrid, both the sleep-related bruxism and activation of the TCR are stabilized. The patented forward bite is very effective at reducing both the sleep-related bruxism events into the normal range as well as the tachycardia, hyperpnea seen with TCR activation.

It should be noted that the Luco Hybrid is the only FDA cleared treatment of sleep p-related bruxism to date. The patented forward bite is unique to this device. All other mandibular advancement appliances have been shown to result in jaw pain within a few weeks to months of use when sleep apnea and sleep-related bruxism occurs together. This can result in abandonment of the appliance and the treatment. This is not seen with the Luco Hybrid, as it treats both the sleep apnea and the sleep-related bruxism providing optimal sleep.

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