Trigeminal nerve and its dental implications

trigeminal as known as dental nerve plays very important role in dentistry
every dental student must have through knowledge about the nerve

1. Trigeminal Nerve and Periodontal Application Presented by Dr. Aishvarya Hajare 1 st year Postgraduate

2. Contents Introduction Anatomy Origin Course Branches Periodontal implications Conclusion References

3. A neuron also known as a neurone or nerve cell is an electrically excitable cell that processes and transmits information through electrical and chemical signals . A typical neuron consists of a cell body (soma), dendrites, and an axon.

4. Ganglion is a nerve cell cluster or a group of nerve cell bodies located in the autonomic nervous system . Ganglia house the cell bodies of afferent nerves. Nucleus is a cluster of densely packed cell bodies of neurons in the central nervous system, located deep within the cerebral hemispheres and brainstem.

5. Introduction Trigeminal nerve is the fifth paired cranial nerve. The great sensory nerve of the head and face, and the motor nerve of the muscles of mastication. The trigeminal nerve is associated with derivatives of the 1st pharyngeal arch.

6. Anatomy Origin The trigeminal nerve originates from three sensory nuclei ( mesencephalic , principal sensory, spinal nuclei of trigeminal nerve) and one motor nucleus (motor nucleus of the trigeminal nerve) extending from the midbrain to the medulla.

7. At the level of the pons, the sensory nuclei merge to form a sensory root. The motor nucleus continues to form a motor root. These roots are analogous to the dorsal and ventral roots of the spinal cord. In middle cranial fossa, the sensory root expands into the trigeminal ganglion.

8. Trigeminal ganglion The trigeminal ganglion is located lateral to the cavernous sinus, in meckel’s cavity, on the anterior surface of the petrous portion of the temporal bone . This depression is known as the trigeminal cave. The ganglia is flat and crescent shaped and measures approx. 1.0x 2.0cms. It is also known as the Gasserian ganglion & Semilunar ganglion.

9. The peripheral aspect of the trigeminal ganglion gives rise to 3 divisions: Ophthalmic ( V1 ) Maxillary ( V2) Mandibular ( V3 )

10. Course: Enters the lateral wall of the cavernous sinus Runs forward below the trochlear and oculomotor nerves . Enters the orbit through the superior orbital fissure External surface of the nose, Anterior nasal cavity Ethmoid sinuses , Sphenoidal sinus Medial eyelids &Eyeball- cornea Lateral part of the upper eyelids, Conjuctiva Lacrimal gland. Cranial dura Frontal sinuses, Upper eyelid Bridge of the nose, Forehead.

11. Ciliary ganglion Ciliary ganglion is a peripheral parasympathetic ganglion placed in the course of the occulomotor nerve It lies near the apex of the orbit between the optic nerve, it has parasympathetic, sensory and sympathetic roots. Parasympathetic root arises from nerve to inferior oblique . Sensory root- comes from nasociliary nerve contains sensory fibers for eyeball. Sympathetic root is branch of internal carotid plexus.

12. Maxillary nerve (V2) Wholly sensory Course : Traverse foramen rotundum post. wall of pterygopalatine fossa enters the inferior orbital fissure enter infra orbital canal emerges on face as infraorbital nerve

13. In the cranial cavity: Meningeal (to dura mater ) In pterygopalatine fossa : Ganglionic- connected to PP ganglion; contain lacrimal secretomotor & sensory fibres from orbital periosteum and mucosa of nose , palate and pharynx. In the pterygopalatine fossa Zygomatic nerve ; it divides into zygomaticotemporal and zygomaticofacial supply the cheek and temple .

14. Pterygopalatine ganglion

15. Pterygopalatine nerves supply the orbit, nose & palate. The nasopalatine nerve leaves nasal cavity enters incisive foramen & supplies gingiva adjacent to maxillary central and lateral incisors. The palatine branches are greater and lesser (palatal soft tissues and area around premolars) Posterior superior alveolar nerve ; supplies maxillary buccal gingiva of premolars and molars. It enters bone supplies the distobuccal and lingual roots of 1st molar In the infraorbital canal:Supplies skin of nose, lower eyelid, and upper lip Middle- premolars and the mesiobuccal root of maxillary molar Anterior-the maxillary anterior teeth On face: inferior palpebral lateral nasal superior labial

16. Mandibular nerve(V3)

17. Origin The mandibular nerve is the largest division of the trigeminal nerve. It is mixed nerve with two roots : a large sensory root & a smaller motor root. The sensory root of the v3 originates at the inferior angle of the trigeminal gangilion , whereas the motor root emerges from the medulla oblongata. The two roots emerge from the cranium separately through the foramen ovale , the motor root lying medial to the sensory. They unite just outside the skull & form the main trunk of the third division. The trunk remains undivided for only 2 to 3 mm before it splits into small anterior and large posterior.

18. i. Branches from the undivided nerve A. Nervous spinosus – the nervous spinosus arises outside the skull and then passes into the middle cranium fossa to supply the dura and the mastoid cells. B. Nerve to the medial pterygoid muscle – a motor root passes to innervate the medial pterygoid muscle. And the it gives off branches to tensor veli palatini and tensor tymphani muscles.

19. ii Branches from the divided nerve Anterior division The anterior division is smaller than the posterior division. It receives sensory and motor fibers that supply the muscles of mastication, the skin and mucous membrane of the cheek and the buccal gingivae and lower molars. It passes downward and forward, where it divides 1. Branch to the lateral pterygoid muscle. 2. Branch to masseter 3. Branch to temporal muscles a. Ant. Deep temporal nerve b. Post. Deep temporal nerve 4. Buccal (long buccal ) nerve

20. Pterygoid nerve. It enters the medial side of the lateral pterygoid muscle to provide its motor supply. 2. Masseter nerve. Passes above the lateral pterygoid to transverse the mandibular notch and enter the deep side of the masseter muscle. 3. Nerves to the temporal muscle a. Ant deep temporal nerve. This nerve passes upward & crosses the infratemporal crest of the sphenoid bone and ends in deep part of anterior portion of temporal muscle. b. Post deep temporal muscle. This nerve passes upward to the deep part of temporal muscle.

21. 4. Buccal nerve – usually the buccal nerve passes downward, anteriorly and laterally between the two heads of the lateral pterygoid muscle. At above the level of occlusal plane of mand . 3 rd and 2 nd molar, it divides into several branches that ramify the buccinator muscle. Sensory fibers are distributed to the skin of cheek, Buccal gingiva of the mandibular molars and the mucobuccal fold of that region.

22. B. Posterior division ; large posterior division is mainly sensory but it carries some motor components. 1. Auriculotemporal nerve – it arises by medial & lateral root. These roots embrace the middle meningeal artery and unite behind the artery just below the foramen spinosum . The united nerve passes posteriorly deep to the external pterygoid muscle , and then between the spenomandibular ligament and the neck of the condyle of the mandible. It transverses the upper part of parotid gland & crosses the posterior part of zygomatic arch. It passes with superficial temporal artery in its upward course and divides into tragus of the pinna of the external ear, to the scalp about the ear and finally upward the skull.

23. Communication with the facial nerve, providing sensory innervation to skin over motor innervation of facial nerve: the zygomatic , buccal and mandibular Communication with otic ganglion, providing sensory secretomotor and vasomotor fibers to parotid gland The anterior auricular branches supplying skin over helix and tragus of ear Branches to external auditory meatus, innervating the skin over meatus and tymphanic membrane Articular branches to the posterior portion of TMJ Superficial temporal branches supplying the skin over temporal region.

24. Lingual nerve At first it passes medially to the lateral pterygoid muscle then as it descends, lies between the medial pterygoid muscle and ramus of mandible in the pterygomandibular space. Chorda tymphani Lingual nerve Inferior alveolar nerve

25. LINGUAL NERVE

26. It runs anterior and medial to inferior alveolar nerve whose path it parallels, then continues downward and forward deep to ptyergomandibular raphe below the superior constrictor . To reach the side of base of tongue , it lies just below mucous membrane Proceeds anteriorly across the muscle of tongue, looping downward and medial to submandibular duct to the deep surface of sublingual gland , where it breaks up into terminal branches.

27. Communication of the lingual nerve with the chorda tympani branch of the facial nerve As the lingual nerve passes medially to the external pterygoid muscle, it is jointed from behind by the chorda tymphani nerve.

28. Nerve fibers from the chorda tympani hitchhike along the LN as special sensory fibers to provide taste sensation from the anterior two-thirds of the tongue and presynaptic parasympathetic fibers to the submandibular ganglion .

29. The secretory fibers of the chorda tymphani nerve pass to the submandibular ganglion, where they synpase . The secretory nerve fibers to the sublingual gland join in a small branch from the submandibular ganglion to rejoin the lingual nerve and pass with this nerve to the sublingual gland Chorda tymphani

30. Position of LN in Third Molar Region As the LN courses anteriorly to the retromolar region, it follows the contours of the medial aspect of the mandible . Lingual nerve lies inferior & lingual to the crest of lingual plate of mandible with a mean position of 2.28mm(±0.9)below the crest & 0.58mm (±0.9 ) medial to crest - Kiesselbach & Chamberlain MRI study demonstrated that the nerve is located at a mean distance of 2.53mm medial to and 2.75mm below alveolar crest

31. Kiesselbach Miloro Pogrel

32. Inferior alveolar nerve It passes downward on the medial side of the lateral pterygoid muscle and the medial side of mandibular ramus. On the medial side of the ramus in the pterygomandibular space, it enters the mandibular foramen. Within pterygomandibular space the inferior alveolar nerve descends in the inferior alveolar canal and its distributed throughout the body of mandible.

33. It travels along with artery and vein anteriorly in the canal as forward as mental foramen where the nerve divides into terminal branches : The incisive nerve and the mental nerve.

34. The variations in the course of IAC are frequent. ( Nortje ´ et al.1977; Berberi et al. 1994; Anil et al. 2003 ) Liu et al (2009) OPG classification of the course of the nerve Linear spoon shaped elliptic arc turning curve

35. A . Gershenson H, Nathan E, Luchansky . Mental Foramen and Mental Nerve : Changes with Age Acta Anatomica.1986;126:21-28

36. Anterior loop of IAN IAN courses inferiorly and anteriorly and then loops back to emerge from the foramen. Arzouman et al. Observations of the Anterior Loop of the Inferior Alveolar Canal. International Journal of Oral & Maxillofacial Implants. May/Jun1993, Vol. 8 Issue 3, p1-11 .

37. Loop dimensions – on radiographs (0-7.5mm), on cadaver specimens (0-1mm), on panoramic radiographs (0.5-3.0mm) Greenstein G et al The mental foramen and nerve: clinical and anatomical factors related to dental implant placement: a literature review. J Periodontol . 2006 Dec;77(12):1933-43.

38. Mandibular foramen The mandibular foramen was located 4.12 mm below the occlusal plane at the age of 3 . By the age of 9, it had reached approximately the same level as the occlusal plane . The foramen continued to move upward to 4.16 mm above the occlusal plane in the adult group. Hwang TJ et al. 1990 Age changes in location of mandibular foramen Dental Association Of Republic Of China

39. Mental nerve Incisive nerve

40. The Mental nerve passes upward, backward & outward to emerge from the mandible via the mental foramen between & just below the apices of the premolar teeth. It immediately divides into three branches . Two of which pass upward & forward to form an incisor plexus labial to the teeth, supplying the gingiva.

41. From this plexus & the dental branches, fibers turn downwards & then lingually to emerge on the lingual surface of the mandible on the posterior aspect of symphysis or opposite the premolar teeth; probably communicating with the lingual or mylohyoid nerve. The third branch of mental nerve passes though the intermingled fibers of depressor anguli oris & platysma to supply the skin of lower lip & chin.

42. Position on mental foramen SINGH, R. & SRIVASTAV, A. K. Study of position, shape, size and incidence of mental foramen and accessory mental foramen in Indian adult human skulls. Int. J. Morphol ., 28(4):1141-1146, 2010

43. Incisive nerve- in mandibular canal, the inferior alveolar nerve runs downward & forward, generally below the apices of teeth until below the first & second premolars. The incisive branch continues forward in the bony canal or in plexiform arrangement , giving off branches to the first premolars, canine & incisors teeth & associated labial gingiva.

44. Nerve to Mylohyoid It branches from the inferior alveolar nerve before the latter’s entry into the mandibular canal. It runs downward and forward in the mylohyoid groove on the medial surface of the ramus and along the body of mandible to reach the mylohyoid muscle and the anterior belly of diagastric .

45. Otic ganglion Small , fusiform, between mandibular nerve and tensor tympani. Peripheral parasympathetic ganglion Connected functionally with glossopharyngeal nerve.

46. The preganglionic parasympathetic fibres originate in the inferior salivatory ganglion of the glossopharyngeal nerve . They leave the glossopharngeal nerve by its tympanic branch and then pass via the tympanic plexus and the lesser petrosal nerve to the otic ganglion.

47. Here, the fibres synapse, and the postganglionic fibers pass by communicating branches to the auriculotemporal nerve , which conveys them to the parotid gland. They produce vasodilator and secretomotor effects

48. Its sympathetic root is derived from the plexus on the middle meningeal artery. It contains post-ganglionic fibers arising in the superior cervical ganglion. The fibers pass through the ganglion without relay and reach the parotid gland via the auriculotemporal nerve. They are vasomotor in function .

49. The sensory root comes from the auriculotemporal nerve and is sensory to the parotid gland . The motor fibers supplying the medial pterygoid and the tensor palati and the tensor tympani pass through the ganglion without relay . The ganglion is connected to the chorda tympani nerve and also to the nerve of the pterygoid canal. These pathways provide an alternate pathway of taste from the anterior two thirds of the tongue.

50. Submandibular ganglion Small, fusiform, present on upper part of hyoglossus Superficial to deep part of submandibular Gland Connected functionally to facial nerve

51. Sympathetic fibres from the external carotid (facial artery) plexus pass through the submandibular ganglion. Preganglionic parasympathetic fibers from the superior salivatory nucleus of the Pons, via the chorda tympani and lingual nerve, which synapse at this ganglion. Postganglionic parasympathetic fibers are distributed to the oral mucosa and the submandibular and sublingual salivary glands. They are secretomotor to these glands. Branches : to submandibular and sublingual glands.

52. Applied Anatomy Trauma, tumors, aneurysms or meningeal infections will caus e : Paralysis of muscles of mastication with deviation of mandible towards the site of lesion. Loss of soft tactile, thermal or painful sensations on the face Loss of corneal reflex and sneezing reflex

53. Trigeminal Neuralgia : This is one of the most common clinical problems of the trigeminal nerve. It is characterized by periods of severe shooting pain in the area of supply of the trigeminal nerve. The pain localizes to the side of the face, and involves the areas of innervation of one or more of the divisions of CN V - usually the maxillary or mandibular divisions. The origin of the pain is unknown .

54. Herpes Zoster : As with other sensory ganglia, the trigeminal ganglion is vulnerable to this infection . This viral infection results in considerable pain and ulceration of the skin and mucous membranes supplied by the affected fibres . The ophthalmic division is most frequently affected .

55. Periodontal ligament and intraosseous anesthetic injection techniques: alternatives to mandibular nerve blocks. The PDL injection and the IO injection are effective anesthetic techniques for managing nerve block failures and for providing localized anesthesia in the mandible . J Am Dent Assoc. 2011 Sep;142 Suppl 3:13S-8S .

56. THE PERIODONTAL LIGAMENT ANESTHETIC INJECTION

57. THE INTRAOSSEOUS ANESTHETIC INJECTION

58. Applied anatomy of implant Posterior superior alveolar nerve may get injured during sinus augmentation with lateral approach, infraorbital nerve may get paresthesized during fixation of implant when inserted through graft and into structure. Subperiosteal implants designed for an atrophic maxilla should not extend into the site of infraorbital nerve and vessels .

59. The potential use of reconstruction techniques on computed tomograhic scans &MRI may increase clincians ability to locate inferior dental canal precisely within the jaw bone. In excessively resorbed the mental foramen within its content of mental nerve and vessels can be found on the crest of ridge. Nerve to mylohyoid is closely related to the ramus of mandible, surgical intervention in this area may lead to injury of important motor nerve which is mylohyoid

60. Conclusion Trigeminal nerve also known as dental nerve sensory supply the head and neck region & motor supply to masticatory muscles thus through knowledge about its course and branches is essential.

61. References Gray’s anatomy 41 st edition B.D. chaurasia vol 3 anatomy of head neck and face Neelima Mallik’s Textbook Of Oral And Maxillofacial Surgery Malamed 6 th edition Texbook of Local anaesthesia Moore PA, Cuddy MA, Cooke MR, Sokolowski CJ. Periodontal ligament and intraosseous anesthetic injection techniques: alternatives to mandibular nerve blocks. J Am Dent Assoc. 2011 Sep;142 Suppl 3:13S-18S Arzouman et al. Observations of the Anterior Loop of the Inferior Alveolar Canal. International Journal of Oral & Maxillofacial Implants. May/Jun1993, Vol. 8 Issue 3, p1-11

62. References cont . Greenstein G et al The mental foramen and nerve: clinical and anatomical factors related to dental implant placement: a literature review. J Periodontol . 2006 Dec;77(12): 1933-43 A. Gershenson H, Nathan E, Luchansky . Mental Foramen and Mental Nerve: Changes with Age Act Anatomica . 1986;126:21-28 Hwang TJ et al. 1990 Age changes in location of mandibular foramen Dental Association Of Republic Of China