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Mylohyoid Line

linea mylohyoidea

The mylohyoid line is an oblique ridge on the inner surface of the body of the mandible, running downward and forward from below the third molar toward the chin. The mylohyoid muscle, which forms the floor of the mouth, arises along it. Above the line lies the sublingual fossa for the sublingual gland, and below it the submandibular fossa for the submandibular gland.

Anatomical Data

Structure & Landmarks

Articulations	No joint; muscular attachment ridge on the mandible
Landmarks	Origin of the mylohyoid muscle Sublingual fossa above (front) Submandibular fossa below (back) Posterior end gives attachment to part of the superior pharyngeal constrictor and pterygomandibular raphe region
Ossification	Part of the mandible, which ossifies in membrane; the ridge becomes more defined as the mylohyoid muscle develops.

Clinical Relevance

Clinical Notes

The mylohyoid line decides where dental infections spread. The roots of the second and third molars usually lie below the line, so abscesses from these teeth tend to drain into the submandibular space, while infection from the front teeth drains above the muscle into the sublingual space. Spread through these spaces on both sides can cause Ludwig angina, a life-threatening swelling of the floor of the mouth. A sharp mylohyoid ridge can also cause pain under lower dentures.

Pathology

Common Injuries & Conditions

Ludwig Angina

A rapidly spreading cellulitis of the floor of the mouth, usually from a lower molar infection, that pushes the tongue up and back and can block the airway.

Submandibular Space Abscess

A collection of pus below the mylohyoid line, typically from infection of the second or third lower molar, causing swelling under the jaw.

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