Trigeminal Nerve

Any effective treatment and diagnosing of a problem can only be done when there is a proper understanding of the anatomy and innervation. To properly understand the dental problems and further actions towards treatment requires the knowledge of trigeminal nerve.
Trigeminal nerve is fifth cranial nerve and is largest among them, it is mixed type i.e. both sensory and motor, supplying most of the face and muscles of mastication.

Trigeminal nerve arises from the three sensory nuclei and one small motor nucleus in the pons and medulla area, the sensory nuclei are mesencephalic nucleus, superior nucleus of trigeminal nerve and spinal nerve of trigeminal nerve along with a small motor nucleus in the medulla region. The fibers from these nuclei form the trigeminal ganglion, from this ganglion arises three divisions of fifth cranial nerve, ophthalmic (v1) maxillary (v2) and mandibular (v3).

Ophthalmic nerve:

Purely sensory division that arises from the superior part of trigeminal ganglion is shortest among the three divisions. After arising it passes anteriorly along the lateral wall of the cavernous sinus and divides into three branches in the anterior most part of the wall. The branches are Lacrimal, Frontal, and Nasociliary. These enter the orbit through superior orbital fissure the frontal and lacrimal entering from the upper part that is outside the common tendinous ring and nasociliary from the middle part that is in the common tendinous ring.
In the orbit the nasociliary nerve gives five branches that include posterior Ethmoid, short ciliary, long ciliary, nerve to ciliary ganglion infra-trochlear and anterior ethmoidal supplying structures of eyeball and around it along with ethmoidal air sinuses.
The frontal gives rise to supra-trochlear and supraorbital nerves supplying the medial aspect of eyelid, skin over medial and lower part of forehead, conjunctiva, scalp, parietal bone and lambdoid suture
Lacrimal nerve supplies the lacrimal gland and this nerve carries the parasympathetic secretomotor fibres from the pterygopalatine ganglion.

Maxillary nerve:

This is the second division of the trigeminal nerve and is also purely sensory. This arises from the middle of the trigeminal ganglion. This nerve gives both direct and indirect branches in the four different regions. The indirect branches are the branches that arise from the pterygopalatine ganglion.

The maxillary nerve gives branches in middle cranial fossa, pterygopalatine fossa, in the infraorbital canal and in the front of the face. In the middle cranial fossa the branch that arises before it exits is the middle meningeal nerve. After exiting the cranium through the foramen rotundum the nerve gives some fibers to the pterygopalatine ganglion without synapsing and along with post ganglionic fibers gives indirect branches. In this region it also gives rise to zygomatic and posterior superior alveolar nerve and passes anteriorly as infraorbital nerve into inferior orbital fissure along with the zygomatic branch.

The nerve in the infraorbital canal gives rise to middle superior alveolar and anterior superior alveolar, supplying the premolar and the anterior teeth, before exiting the canal through the infraorbital foramen. Zygomatic nerve in the orbit divides into zygomaticofacial and zygomaticotemporal branches that move anterolaterally supplying the skin on the prominence of cheek and side of the forehead respectively, it also connects to the lacrimal nerve. After exiting the infraorbital canal it gives out terminal branches of skin that innervate the lower eyelid, nose and the upper lip.

Indirect branches include orbital, posterior superior nasal, posterior inferior nasal, bother greater and lesser palatine, nasopharyngeal. The posterior superior nasal fibers pass along the septum and exit through incisive foramen as a nasopalatine nerve that supplies the premaxillary region. The greater and lesser palatine exit through the greater palatine foramen and lesser palatine foramen respectively, greater palatine innervates the hard palate unilaterally as anterior as premolars and lesser palatine innervates soft palate.

Mandibular nerve:

It is the largest division among the three and also a mixed part of the trigeminal nerve. It arises from the lower part of the trigeminal ganglion and exits the cranium from foramen ovale. The mandibular nerve passes down and divides into anterior and posterior division. It gives branches from the undivided trunk, which are nervous spinosum and nerve to medial pterygoid. The anterior division supplies the muscles of mastication along with one branch of sensory innervation to the buccal mucosa till the premolars, the branches are deep temporal, lateral pterygoid masseteric and buccal (sensory).

The posterior division gives out auriculotemporal nerve lingual nerve inferior alveolar nerve and nerve to mylohyoid, the inferior alveolar nerve gives a branch that exits through the mental foramen called the mental nerve and the portion of the inferior alveolar nerve after the mental foramen is called incisive nerve. These nerves of the posterior branch supply the pulpal innervation of the mandibular teeth and soft tissue of lower jaw, the lingual nerve supply the sensory innervation to anterior 2/3rd of the tongue.

This is a brief anatomy of the trigeminal nerve which is very significant in dentistry.

Contributor- Medico Prashamsh Chandra Kulkarni