Neutral Jaw, Crowded Airway
In sleep, a relaxed tongue can rest right against the throat wall.
- ~936M: Adults with OSA (worldwide, mild-severe)
- #1: Retroglossal site (most common collapse point)
- REM sleep: Muscle tone drop (genioglossus relaxes most)
- 5–15: Untreated mild AHI (events per hour)
Where the airway narrows
The tongue base sits directly across from the pharyngeal wall.
Why sleep makes it worse
Muscle relaxation lets gravity pull the tongue backward.
The resulting airflow problem
A narrow channel vibrates and collapses, producing snoring and apnea.
Appliance Inserted, Jaw Captured
A custom oral appliance links the upper and lower dental arches.
- MAD: Device type (mandibular advancement device)
- 2–4 wks: Typical fit time (titration period)
- Mild–moderate: First-line for (OSA severity)
- Higher: Adherence vs CPAP (better tolerated nightly)
How the splints attach
Custom trays clip over the teeth of both jaws.
The mechanical link
Connecting rods let the lower splint sit forward of the upper.
Before any movement
At insertion the jaw has not yet advanced.
Mandibular Advancement, Millimeter by Millimeter
Clinicians advance the lower splint gradually to find an effective, tolerable position.
- 0–10 mm: Typical protrusion range (from neutral bite)
- 60–70%: Effective protrusion (of maximum comfortable)
- ~0.5 mm: Titration steps (per adjustment)
- TMJ: Jaw joint monitored (for discomfort)
The forward ratchet
Turning the mechanism inches the mandible anteriorly.
Balancing comfort and effect
More advancement helps breathing but stresses the jaw joint.
A patient-specific endpoint
Titration stops at the smallest effective advancement.
Tongue Base Pulled Anteriorly
The genioglossus muscle physically tethers the tongue to the inside of the jaw.
- Genioglossus: Key muscle (tongue-to-mandible tether)
- ~85–90%: Tongue displacement ratio (of jaw movement)
- Moves too: Hyoid bone (anterior-superior shift)
- Secondary: Soft palate effect (lesser tension increase)
A direct mechanical link
Jaw advancement drags the attached tongue base forward with it.
Hyoid and suprahyoid muscles
Nearby structures shift anteriorly along with the tongue.
Not just bone movement
Soft tissue displacement is the real therapeutic mechanism.
Airway Widens, Collapse Risk Falls
A wider retroglossal space lets air flow smoothly instead of vibrating shut.
- ~70–80%: Mild OSA response (AHI reduction achievable)
- Limited: Severe OSA response (often needs CPAP too)
- AHI < 5: Success threshold (commonly defined cure)
- Baseline severity: Candidacy driver (plus anatomy)
Airflow becomes laminar
A wider channel replaces turbulent, collapsing airflow.
Best candidates
Mild-to-moderate OSA responds best to jaw advancement.
A ceiling effect in severe disease
Severe OSA often has anatomy advancement cannot fully correct.