Mandible Anatomy: A Comprehensive Guide
It is the largest, strongest and lowest bone of the face It is U-shaped with an alveolar part that supports the mandibular teeth Inferior to the second premolar teeth are the mental foramina for mental nerves and vessels It has 2 parts; A curved horizontal body Two broad vertical rami
Body Of The Mandible
It is U-shaped It has 2 surfaces (internal and external surfaces)
It also has 2 borders (upper and lower border)
External Surface: Anatomical Features
- Symphysis menti A faint median ridge in the upper part of the external surface, anteriorly which indicates the line of fusion of the two halves of foetal mandible
- Mental protuberance A median triangular elevation in the anterior part of mandible below symphysis menti, of which the base is raised on each side as mental tubercle
- Mental foramen It is on each side of the mandible Below the 2nd premolar tooth or below the interval between the two premolar teeth It transmits mental nerve & vessels
- Oblique line A faint line which ascends backward from each mental tubercle
Mnemonic: Moms Internal Surface: Anatomical Feature
- Digastric fossa One on each side, anteriorly Located near the midline, below the anterior end of mylohyoid line For the anterior belly of digastric
Mandibular Alveoli
Upper border (alveolar part) of mandibular body contains 16 alveoli for the roots of mandibular teeth Following loss of teeth, the sockets begin to fill with bone, and alveolar processes begin to resorb Mental foramen may eventually lie near the upper border of mandibular body In some cases, mental foramina resorption may extend to the mental nerves causing injury and pains
Mylohyoid Line
An oblique line that divides the internal mandibular surface into 2 parts;
- Anterosuperior sublingual fossa (lodges sublingual gland)
- Posteroinferior submandibular fossa (Lodges superficial part of submandibular gland)
Is sharp and distinct near molar teeth Mental spines Above the anterior end of mylohyoid line is a small elevation that bears the mental spines (superior and inferior tubercles)
- Superior tubercle gives attachment to genioglossus; while
- Inferior tubercle gives attachment to geniohyoid
Mnemonic: Dm3 Ramus Of The Mandible
A sagittally-disposed plate of bone Unites with mandibular body almost at a right angle (angle of the mandible)
Its external surface is roughened (for attachment of masseter)
Anatomical Features
- Mandibular foramen On the internal surface of ramus Opens into mandibular canal; and Transmits inferior alveolar nerve and vessels
- Mylohyoid groove Passes downwards and forwards from the mandibular foramen Lodges mylohyoid nerve and vessels Postero-inferior to mylohyoid groove, mandibular ramus (including mandibular angle) is roughened (for medial pterygoid)
- Lingula A small tongue-like piece of bone Projects upwards from mandibular ramus
- Medial to mandibular foramen
- For the attachment of sphenomandibular ligament
The upper end of the mandibular rams has 2 processes; Coronoid process
- Lies anterior to the condylar process
- For attachment of temporalis
Condylar process
- Its expanded upper end is the mandibular head This beats a facet lined by fibrocartilage For articulation with the mandibular fossa of temporal bone at the TMJ
- Just below the head, condylar process is constricted to form the mandibular neck The depression between these processes is the mandibular notch
[Mnemonic: MMLCC]
Ossification Of The Mandible
The mandible develops from:
- A dense fibromembranous tissue located lateral to the inferior alveolar nerve, by intramembranous ossification; and from Meckel’s cartilage Cartilage of the 1st branchial arch (mandibular arch)
- Its perichondrium forms sphenomandibular ligament Ossification commences by 6th week of development from a centre located near the mental foramen The mandible is largely ossified by the end of the 1st year of life
Applied Anatomy Fracture Of The Mandible
May involve the neck, body and angle or coronoid process Usually from trauma; a hard blow, auto/bike accident, a fall, etc Less frequently from tumor or osteonecrosis Commoner in males Condyle, angle most often involved Fracture of mandibular neck may be bilateral and may result in the dislocation of TMJ
CT Scan
Relatively more accurate in its diagnosis than X-ray
Loss Of Mandibular Teeth
Would result in the resorption of mandibular alveolar processes such that the mental foramen lies close to the upper border of mandibular body (or disappears) thereby exposing mental nerve to injury
Infection In The Mandibular Molar Teeth
Could result in cellulitis of the neck
