Nervous Innervation of the Mandibular Teeth

Describe the nerve innervation of the lower teeth (use appropriate anatomical terminology). Explain your friend's lack of sensation in the lips, dry mouth, and alteration of taste if the anesthetic had prevented nervous transmission of anatomically associated structures. And, clarify that your friend's tongue did not lose muscle control when he lost feeling.

There are three main nerves that innervate the mandibular/lower teeth. The inferior alveolar nerve, which is the first nerve, supplies the pulp as well as the investing systems of the mandibular molars, anterior teeth, and premolars. The second nerve is called the lingual nerve which distributes the lingual mucoperiosteum of all the mandibular teeth, front two-thirds of the tongue as well as the surface of the mouth. The last nerve is the long buccal nerve which supplies the buccal mucoperiosteum next to the lower molars. It is important to note that the lower anterior teeth have an incisive nerve which crosses the midline from one side to the other. The lower premolar teeth may also receive extra nerve supply from the cutaneous coli nerve which is a section of the plexus of nerves for the labial mucoperiosteum. Finally, the lower molars may also receive an extra supply of nerves from the nerve to mylohyoid for the pulp and investing structures.

The loss of feeling in the tongue and a dry mouth resulted from the anaesthetization of the inferior alveolar nerve near the mandibular foramen whereby all the sensory stimuli is blocked. The tongue and the mandibular gingiva is anaesthetized at the same time when the inferior alveolar nerve is deadened since the lingual nerve goes underneath the mucosa and very proximate to the inferior alveolar nerve medial to the ramus of the mandible. A change in taste, on the other hand, could have resulted due to the possibility that the nerve for taste could have been contacted by the needle when injecting anesthesia leading to altered taste. The taste nerves to the front two-thirds of the tongue goes along with the similar nerve that conveys sensation to the tongue. This nerve is usually deadened during the dental injection for treatment or removal of teeth involving the lower teeth. The change in taste could be as a result of nerve damage due to the procedure involved in the dental intervention of the lower teeth. The nerve damage could have come from the direct needle trauma causing hemorrhage in the epineurium or a neurotoxic effect of the anesthetic used.

Finally, my friend did not lose motor function to the tongue when he lost sensation. This is because the only nerves that could have been damaged are the inferior alveolar nerve and the lingual/tongue nerve which are both sensory nerves. As such, the damages could not move the motor nerves of the tongue since they do not move muscles. The hypoglossal nerve which provides motor control of the extrinsic and intrinsic muscles of the tongue remained in contact and was not involved during the dental procedure. Since the nerve has a close proximity to other structures such as other nerves, veins, and arteries, it is very rare for it to be damaged. The nerve carries lower motor neurons that synapse with the upper motor neurons in the hypoglossal nucleus, and since it was not damaged, he did not lose motor function of the tongue when he lost sensation. If at all the nerve could have been damaged, then this would have led to wasting of the muscles of the tongue and a deviation towards the affected side because of the weaker genioglossal muscle.

Work Cited

Blanton, Patricia L., and Arthur H. Jeske. "The key to profound local anesthesia: neuroanatomy." The Journal of the American Dental Association 134.6 (2003): 753-760.

DeSantis, James L., and Charles Liebow. "Four common mandibular nerve anomalies that lead to local anesthesia failures." The Journal of the American Dental Association 127.7 (1996): 1081-1086.

Hersh, Elliot V., et al. "Assessing the duration of mandibular soft tissue anesthesia." The Journal of the American Dental Association 126.11 (1995): 1531-1536.

Rood, J. P. "The analgesia and innervation of mandibular teeth." British dental journal 140.7 (1976): 237.

Stein, Pamela, Jennifer Brueckner, and Matthew Milliner. "Sensory innervation of mandibular teeth by the nerve to the mylohyoid: implications in local anesthesia." Clinical Anatomy 20.6 (2007): 591-595.

Wilson, Stephen, Priscilla Johns, and Peter M. Fuller. "The inferior alveolar and mylohyoid nerves: an anatomic study and relationship to local anesthesia of the anterior mandibular teeth." The Journal of the American Dental Association 108.3 (1984): 350-352.