How jaw-advancing mouthpieces work

What’s going on

When you fall asleep, the muscles in your throat relax. In many people, the tongue and soft tissue sag back and narrow the airway. Air squeezing through the narrow space makes the tissue vibrate, and that vibration is snoring.

A mandibular advancement device (MAD) is a mouthpiece that holds your lower jaw (the mandible) a little forward. Your tongue is attached to the inside of the jaw, so it moves forward with it. Cleveland Clinic puts it simply: moving the jaw forward pulls the tongue forward and makes more space for air at the back of the throat.

The ADA describes the same thing. Advancing the jaw moves the base of the tongue forward and enlarges the space behind it. The FDA files for store-bought devices use similar words: they widen the upper airway to reduce the air turbulence that causes snoring.

What the airway does

Researchers have looked inside the airway with a camera while people wore these devices. In one small study of 15 people with sleep apnea, the device widened the airway. The biggest change was behind the soft palate, and mostly from side to side, not just front to back.

So the effect isn’t only about the tongue moving out of the way. A later trial summarized by the ADA found these devices also shift the muscles around the airway. The camera study was done while people were awake, so its authors were cautious about how it applies during sleep.

How far the jaw moves

The shift is small, a few millimeters. SnoreRx’s FDA file, for example, describes advancement of up to 6 mm, and the maker says it adjusts in 1 mm steps.

More isn’t always better.

One clinical study looked at custom appliances for sleep apnea. Benefit rose as the jaw moved forward, then leveled off at about 70% of each person’s maximum forward reach. The best position differed a lot from person to person.

That study involved dentist-fitted devices and sleep testing, not store-bought mouthpieces. The point it makes still applies: the right amount of advancement is personal.

Why the jaw is moved forward slowly

Adjusting the jaw position in small steps over time is called titration. The AASM and AADSM guideline compares it to adjusting the pressure on a CPAP machine.

With a custom appliance, a dentist adjusts the position at follow-up visits, sometimes guided by a sleep test the physician orders. With an adjustable store-bought mouthpiece, you make the changes yourself.

A sensible home approach:

1. Start at the smallest setting the maker allows.
2. Wear it for several nights before changing anything.
3. Move forward one step at a time only if the snoring continues.
4. Stop moving forward if your jaw, teeth or bite feel sore. Go back a step and see a dentist if it doesn’t settle.

The main designs

Adjustable (titratable)

These let you change how far the jaw sits forward. The guideline defines them as devices with a mechanism that allows varying amounts of jaw protrusion.

SnoreRx and VitalSleep are store-bought examples. When a dentist treats sleep apnea, the guideline suggests a custom, adjustable appliance.

Fixed (non-titratable)

These hold the jaw in a single position. The guideline notes that no changes are possible over the course of treatment.

Some are one piece, called a monobloc. Others come in a few preset sizes, and you choose the size instead of adjusting it.

One piece or two

• One piece (monobloc): the upper and lower trays are joined solid. One small trial of custom devices for sleep apnea found a monobloc reduced breathing pauses more than a two-piece design.
• Hinged one piece: a flexible hinge joins the trays, so your mouth can open a little.
• Two piece: separate upper and lower trays link together. SnoreRx is built this way, and the link between the trays is what you adjust.

The research comparing designs is thin. The best design is the one you’ll wear every night without pain.

Tongue-retaining devices, compared

A tongue-retaining device Weak doesn’t move the jaw. It holds your tongue forward using suction, as Cleveland Clinic describes.

The ADA says these devices are rarely used, mainly when dental reasons rule out a jaw-advancing one. Dentures or too few teeth for a mouthpiece to grip are examples.

The AASM and AADSM guideline found too little evidence to assess them for sleep apnea. With your tongue held forward, you’ll need to breathe comfortably through your nose.

A jaw-advancing mouthpiece Strong has the stronger evidence for snoring.

What a dentist or doctor can do

A physician can decide whether your snoring needs a sleep test. If a physician orders an oral appliance, a dentist trained in dental sleep medicine can make a custom one and adjust it over follow-up visits.

Before trying any mouthpiece, check that none of these apply to you:

• Under 18
• Central sleep apnea
• Loose teeth or gum disease
• Dentures or braces
• Jaw joint problems
• Recent implants or major dental work The who shouldn’t use a snoring mouthpiece page explains why.

To see how store-bought options compare, go to anti-snoring mouthpieces compared. For what to expect in the first weeks, read side effects.