Innervation of teeth and jaws

Sources of innervation and the trigeminal ganglion

Oral cavity organs are innervated not only by the trigeminal nerve. Sensation is also provided by the glossopharyngeal and vagus nerves, while branches of the cervical plexus innervate specific facial areas. Sympathetic innervation of tissues comes from the superior cervical sympathetic ganglion.

However, the main source of sensory innervation is the trigeminal nerve (n. trigeminus). Its pseudounipolar cells lie in the trigeminal (Gasserian) ganglion, located at the base of the skull. Three branches arise from the ganglion:

1. Ophthalmic nerve (V1): exits through the superior orbital fissure. It is not involved in the innervation of teeth and jaws.
2. Maxillary nerve (V2): leaves the skull through the foramen rotundum (foramen rotundum).
3. Mandibular nerve (V3): exits through the foramen ovale.

Along the path of these branches lie five autonomic ganglia: ciliary (associated with V1), pterygopalatine (V2), as well as otic, submandibular, and sublingual (V3).

Maxillary innervation (branch II)

The maxillary nerve (n. maxillaris) is exclusively sensory. Having entered the pterygopalatine fossa, it gives off several branches and continues as the infraorbital nerve (n. infraorbitalis).

Emerging onto the face through the infraorbital foramen, this nerve divides into terminal branches, forming the minor goose foot (pes anserinus minor). It innervates the upper lip, lower eyelid, and nasal wings.

The maxillary teeth themselves receive innervation from the posterior superior alveolar branches (usually 4 to 8), which are divided into two groups:

• Extrabony: descend along the maxillary tuberosity, innervating the periosteum, gingiva, and buccal mucosa at the level of molars and premolars.
• Intrabony: penetrate into the bone canals of the maxilla, providing sensation to the molars, the tuberosity itself, and the maxillary sinus mucosa.

Brainstem nuclei and motor fibers

Central processes of trigeminal ganglion cells head toward the brainstem nuclei, which extend continuously from the cervical spinal cord to the midbrain:

• Pontine (principal sensory) nucleus: responsible for tactile and discriminative sensation.
• Spinal trigeminal nucleus: responsible for pain and temperature sensation. It has a strict somatotopic organization (inverted facial projection). It is well established that pain impulses from dental pulp arrive at its middle part (pars interpolaris).
• Mesencephalic nucleus: receives proprioceptive impulses from muscle spindles of the masticatory muscles. This is a unique structure—essentially a peripheral ganglion shifted inside the CNS.

From the secondary neurons, sensory pathways decussate, ascend to the thalamus, and from there tertiary neurons proceed to the postcentral gyrus of the cortex.

Motor fibers originate from a separate nucleus in the pons, exit the skull through the foramen ovale along with V3, and innervate the masseter, temporal, pterygoid, mylohyoid muscles, and the anterior belly of the digastric muscle.

Interconnection of the dentofacial system and ENT organs

The anatomical and physiological proximity of the dentofacial system and upper respiratory tract determines their close mutual influence:

• Referred pain: due to shared innervation, toothache can be a symptom of inflammation in the maxillary sinus or external auditory meatus. Conversely, pathology of the temporomandibular joint or teeth can radiate pain to the ear, throat, or nose.
• Impact of breathing type: persistent nasal breathing impairment forces the patient to breathe through the mouth. This dries out the mucous membrane, makes it harder to clear the oral cavity of food debris, disrupts enamel nourishment, and alters the microflora. The result is the development of caries, stomatitis, and gingivitis. In addition, decreased masticatory load during mouth breathing promotes malocclusion.
• Odontogenic pathologies: dental and periodontal diseases frequently become the primary cause of inflammatory processes in the maxillary sinus (sinusitis).

Class and exam questions

What else to study on this topic

• Topography and innervation zones of the terminal branches of the mandibular nerve (lingual, buccal, mental).
• Somatotopic organization of the spinal trigeminal nucleus.
• Afferent connections of the spinal tract with cranial nerve pairs VII, IX, and X.
• Clinical presentation of trigeminal motor fiber lesions (flaccid paresis of masticatory muscles).
• Congenital malformations of the maxillofacial region (cleft lip and palate) and their impact on ENT organs.

Other topics in the "Anatomical Structures" section

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.