Dental and Facial Pain

Ahmad Elsharydah

Background

Orofacial pain is a pain generated from the different structures of the face and the head. It is the most common reason for patients to seek medical care. The main source of orofacial pain is the dental and the periodontal regions.¹ The oral pain in general can be divided into odontogenic pain (tooth pain) and nonodontogenic pain. The odontogenic pain originates from the different dental structures such as tooth pulp and periodontal structures. On the other hand, the nonodontogenic pain may come from various intraoral structures such as gums and mucosa. The innervation of these components are complex, therefore may generate pain with different types of mechanisms. Detailed history, physical examination, and review of the available laboratory and imaging studies would help to differentiate the different types of orofacial pain and make a diagnosis. The first step to manage acute orofacial pain is management of the source disease or condition. Symptomatic therapies include the use of pharmacological agents, nonpharmacological treatment such as heat or cold, and nerve blocks. Table 44.1 lists the differential diagnosis of the orofacial pain (American Academy of Orofacial Pain classification).

This chapter is a concise summary for the assessment and management of patients with acute orofacial pain based on the available scientific evidence.

Epidemiology of Orofacial Pain

Orofacial pain is a very common pain problem. Some demographic studies have shown that >39 million people, 22% of the U.S. population, report pain in the orofacial region.² One study reported that more than 81% of the population has some type of significant jaw pain in their life time.³ Orofacial pain is rarely an isolated complaint; it is commonly part of other conditions. The overall reported prevalence of orofacial pain is 1.9%-26%.⁴,⁵ Orofacial pain is more prevalent in women and young adults (18-25)⁴ than in men and older adults.

Neurophysiology and Neuroanatomy for Orofacial Pain

It is important for the clinician managing patients with acute or chronic orofacial pain to understand the basic neuroanatomy and neurophysiology of this type of pain. Most of the orofacial pain pathways communicate through the trigeminal nerve,⁶ the largest and most complex cranial nerve. They are mostly transmitted by sensory, motor, and autonomic nerve networks. To better understand orofacial pain, it is an essential to understand the peripheral and the central connection of the trigeminal nerve system. It is out of the scope
of this chapter to describe the details of these connections. In general, nociceptors in the facial and oral regions are responsible for the recognition of proprioception, mechanical stimuli, thermal stimuli, and pain perception.⁷ Trigeminal nerve (via afferent fibers A, B, and C) is the dominant nerve that relays sensory impulses from the orofacial area to the central nervous system. The facial nerve, the glossopharyngeal nerve, the vagus nerve, and the upper cervical nerves (C2 and C3) also transmit sensory information from the face and surrounding area. The upper cervical nerves provide innervation to the back of the head, lower face, and neck. More importantly, they converge in the brainstem at the trigeminal nucleus. Most nociceptive orofacial pain impulses are transmitted by the somatic nerves, a significant portion is transmitted by autonomic nerves and a small portion may be transmitted by motor nerves.

TABLE 44.1 DIFFERENTIAL DIAGNOSIS OF OROFACIAL PAIN (AMERICAN ACADEMY OF OROFACIAL PAIN CLASSIFICATION)

Intracranial pain disorders	Neoplasm, aneurysm, abscess, hemorrhage, hematoma, edema
Primary headache disorders (neurovascular disorders)	Migraine, migraine variants, cluster headache, paroxysmal hemicrania, cranial arteritis Carotidynia, tension-type headache
Neurogenic pain disorders	Paroxysmal neuralgias (trigeminal, glossopharyngeal, nervus intermedius, superior laryngeal) Continuous pain disorders (deafferentation, neuritis, postherpetic neuralgia, posttraumatic and postsurgical neuralgia) Sympathetically maintained pain
Intraoral pain disorders	Dental pulp, periodontium, mucogingival tissues, tongue
Temporomandibular disorders	Masticatory muscle, temporomandibular joint, associated structures
Associate structures	Ears, eyes, nose, paranasal sinuses, throat, lymph nodes, salivary glands, neck

Heterotopic and referred pain are common in the acute and chronic orofacial pain conditions. Orofacial heterotopic pain occurs when the source of pain is not located in the region of pain perception; and referred pain describes pain felt at a location served by one nerve, but the source of nociception arrives at the subnucleus caudalis of the trigeminal nerve by a different nerve. The heterotopic and referred phenomena explained by the complexity of the trigeminal network and the convergence of multiple sensory nerves carrying input to the trigeminal spinal nuclei from cutaneous and deep tissues located throughout the head and neck set the stage for referred pain.⁸

Acute Orofacial Pain

Acute orofacial pain is a very common complaint. In most of the cases, acute orofacial pain is a symptom of other conditions involving the face and/or the oral cavity including trauma, surgery, infections. Most of chronic orofacial pain conditions stem from untreated and poorly controlled acute orofacial pain. Postoperative orofacial pain management is similar to other acute postoperative management including the use of pharmacological agents, nonpharmacological therapies such as heat or cold, and nerve blocks. In this section, I will briefly mention the different conditions causing acute orofacial pain and the specific management for these conditions. Table 44.2 summarizes the common topical medications used for orofacial pain management.

TABLE 44.2 TOPICAL MEDICATIONS USED TO TREAT OROFACIAL PAIN

Type	Generic Name	Dosage	Form
Topical local anesthetics	Lidocaine	2%	Gel Viscous solution Ointment Spray Lozenge
		4% or 5%	Adhesive patch
	Benzocaine	20%	Aerosol Gel Lozenge Liquid Ointment Mouth strip Mouth swap
	Lidocaine/prilocaine	2.5% lidocaine/2.5% prilocaine	Cream Periodontal gel
Nonsteroidal anti-inflammatory drugs	Ketoprofen	10%-20%	Cream Patch
Nonsteroidal anti-inflammatory drugs	Diclofenac	10%-20%	Gel Patch Solution
Neuropeptide	Capsaicin	0.025% or 0.075%	Cream Liquid Gel Patch Lotion
Sympathomimetic agent	Clonidine	0.01%	Gel Cream Patch
NMDA antagonist	Ketamine	0.5%	Cream
Anticonvulsant	Carbamazepine	2%	Cream
Antidepressant	Amitriptyline	2%	Gel Cream
NMDA, N-methyl-D-aspartate. Modified from Halpern L, Willis P. Orofacial pain: pharmacologic paradigms for therapeutic intervention. Dent Clin North Am. 2016;60:381-405.