Odontogenic Pain

Odontogenic pain refers to pain that initiates from teeth or the periodontium, the maxilla or the mandible. A “toothache” is caused by inflammation of the dental pulp, often due to dental caries (tooth decay). Periodontal disease is a common cause of infection that can produce odontogenic pain (). The source of odontogenic pain is the pulpo-dentin complex and periapical tissue. In healthy pulp, thermal stimuli produce short, sharp pain that lasts approximately 1 to 2 seconds (). This indicates that the nerve fibers are functioning. A response to cold indicates vital pulp, whereas an increased response to heat suggests a pulpal or periapical pathology that may require endodontic treatment.

• Dental pulpitis (inflammation of the pulp) can be due to caries present near the pulp. It is classified as reversible or irreversible.

  • In reversible pulpitis, the pulp can remain viable if treated, which typically requires removal of the caries followed by restoration. It is characterized by short, quick bursts of pain induced by a cold stimulus that ceases immediately upon its removal.

  • Irreversible pulpitis occurs when the pulp is damaged beyond repair. It is characterized by intense pain and is one of the most common reasons for emergency dental visits. As the inflammation spreads, the cellular organization of the pulp breaks down. It is typically associated with tooth decay, a cracked tooth, or trauma. Management for irreversible pulpitis is either pulpectomy (root canal treatment) or tooth extraction. Pain symptoms with irreversible pulpitis include:

    • Intense persisting pain with warm stimulus. After removal of the stimulus, the pain becomes dull and pulsating. Early pain information is carried on both A-d and C fibers; however, as the inflammation progresses, C fibers become the predominant carriers for pain transmission.

    • Pain subsides with cold stimulus, likely due to vasoconstriction and a decrease in intrapulpal pressure. This symptom is highly indicative of necrotic pulp.

    • When C fibers become the predominant mode of transmission, the pain becomes more diffuse and is more difficult to localize.

    • Intense and prolonged pain can refer to the ear, temporal area, and the cheek.

    • Once the periapical tissue becomes involved, the tooth becomes sensitive to percussion.

  • Necrotic pulp results from continued degeneration of inflamed pulp. There is no reparative potential. In addition to the moderate to severe spontaneous pain, the patient may experience swelling in the jaw and lymphadenopathy. Pain receptors in necrotic pulp often become damaged and may not respond to thermal stimuli. If the pulp is only partially affected, there may be some response present.

• Periapical pain can be caused by an infection spreading through the apical foramen of the tooth into the periodontal region. The infection can transform into a dental abscess if left untreated.

• Exposed cementum and dentin on teeth can produce pain. Under ordinary circumstances, tooth sensitivity can be present with healthy pulp. If gingival recession is present, the patient underwent recent scaling, or they suffer from gastric reflux, there can be dentin sensitivity. The pain is described as sharp and short in duration. It is thought that the pain is due to movement of fluids in and out of the dentin tubules in response to osmotic or temperature changes.

• Incomplete fractures of a tooth may cause pain. Patients often complain of sharp pain when they bite or release from biting. Symptoms may also include sensitivity to cold temperatures. Cracks are often difficult to see in the oral cavity and may not show up on radiographs.

• Periodontal disease is a chronic inflammatory disorder initiated by oral microbes that can eventually affect supporting structures of the tooth and the surrounding bone. In general, it is not considered a chronic pain disorder, as initial symptoms are gingival sensitivity and bleeding. However, periodontal abscesses can develop. This type of acute infection does not develop from the pulp but typically arises in a preexisting periodontal pocket. In this situation, the most common symptom is pain. Other symptoms include swelling of the gingiva and oral mucosa surrounding the affected tooth. Lymphadenopathy and fever may be present.

• Alveolar osteitis or “dry socket” is one of the most common complications following a tooth extraction. In this condition, the clot that developed post extraction fails, leaving an empty socket and exposed alveolar bone. Bone pain can result from noxious stimulation of the periosteum. Additionally, food and debris can get trapped and become necrotic, further irritating the nerve endings. Pain from a dry socket is typically described as dull and throbbing. Smoking is a major factor in the development of a dry socket, most likely due to the reduction in blood supply. Alveolar osteitis rarely occurs in the maxilla and generally develops 3 to 5 days following a mandibular tooth extraction.

Mucosal Pain

Pain in the oral mucosa is typically associated with mucosal lesions caused by local or systemic diseases. Mucosal pain can be localized or diffused. Local pain is often associated with breaks in the mucosa such as an ulcer or erosion. Diffuse pain can be caused by an infection or other factors such as a systemic condition. Acute mucosal pain is usually related to tissue damage; thus, it typically responds to treatment and/or heals in a relatively short period. Chronic mucosal pain can last from months to years after healing and in the absence of obvious stimuli (lesions) (see Section 26.3).

A significant amount of oral mucosal disorders causing pain is due to the formation of ulcers or erosions. A mucosal erosion is a superficial break in the mucus membrane. A mucosal ulcer is defined as loss of surface tissue and degeneration of both the epithelium and the lamina propria. It involves the submucosa and can even run as deep as the muscle or the periosteum. Mouth ulcerations can develop from a number of situations including poorly fitting dentures, systemic disease, and iatrogenic or treatment-related causes.

• Lesions of odontogenic origin:

  • Dental and periodontal issues primarily affect the gingiva and adjacent alveolar mucosa. Dental abscesses originating from necrotic pulp often produce swelling in the mucosa.

  • Gingivitis or inflammation of the gingiva is commonly the result of dental plaque and can cause discomfort in individuals. Factors other than dental plaque that are related to gingivitis are orthodontic brackets, mouth breathing, and pregnancy.

• Lesions caused by poorly fitting dentures:

  • Irritation from dentures affects the alveolar ridge and palate.

  • Acute and severe irritation can produce significant ulcerations.

  • Chronic irritation results in a proliferative response that mimics the shape of the denture.

  • As the alveolar bone is continuously resorbed, the denture sits more deeply in the sulcus, exacerbating the ulcerative condition.

  • Maxillary dentures that are poorly adapted to the palate can produce papillary hyperplasia (polyps).

• Lesions caused by trauma:

  • Trauma to the oral mucosa from biting, rubbing on sharp edges of teeth, or restorations can result in the formation of ulcers.

    • These types of ulcerations can appear very similar to carcinomatous lesions so care must be taken to rule out malignancy.

  • Milder trauma can produce hyperkeratinization or fibroepithelial hyperplasia, which can become an irritant resulting in pain.

  • Thermal and chemical burns to the oral mucosal can also cause pain.

• Recurrent aphthous ulcers (canker sores) in the oral mucosa are fairly common. The incidence has been reported as high as 20% of the general population.

  • Lesions are sharply demarcated, round to ovoid with erythematous halos.

  • These lesions will typically heal within 1 week. Ulcers lasting longer than 3 weeks should be evaluated for possible malignancy or other underlying diseases.

  • Although there are some cases where there appears to be a genetic basis, most individuals develop ulcers randomly. Factors associated with the development of aphthae include stress, menstruation, pregnancy, and food allergies. Aphthae are also common in HIV, Crohn’s disease, and celiac disease, among others.

• Mucocutaneous pain:

  • Oral lesions are very common in mucocutaneous diseases such as lichen planus, pemphigus vulgaris, erythema multiforme, and chronic ulcerative stomatitis ().

  • These diseases produce erosive and ulcerative lesions that are extremely painful.

Musculoskeletal Pain

Temporomandibular disorders (TMD) are the most common nondental cause of orofacial pain. Musculoskeletal pain from TMD is primarily extra oral and typically localizes around the TMJ and muscles of mastication. It can also produce headaches and pain within the ear (otalgia; see Chapter 23).

• Myalgia is defined as pain caused by jaw movement or palpation of the masseter or temporalis. Myalgia typically presents as dull aching pain. It is commonly seen as acute, but with continued muscle strain, it can last for long periods of time.

• If pain radiates to adjacent structures, it is termed myofascial pain.

• Myofascial pain also presents as dull, aching, continuous pain that may refer to other sites upon palpation. Myofascial pain tends to be chronic and may have trigger points that, when stimulated, will elicit pain.

• Myositis (inflammatory myopathy) refers to any condition that results in inflammation of muscles. In dentistry, it refers to localized, transient swelling that involves facial muscles and tissues. Myositis can occur following dental anesthesia or trauma. Pain may be increased with mandibular movement.

• Acute articular disk displacement is often associated with pain, whereas chronic disk dislocation is more likely to be nonpainful. Disorders of the disk often produce clicking or crepitus. Osteoarthritis of the articular disk often results in deterioration of the articular surface. This condition can result in intense pain that is exacerbated by mandibular movement.

Referred Pain

Referred pain is a phenomenon whereby pain is felt in an area that is remote from the actual location where the nociceptors were stimulated. Although the mechanisms behind referred pain are not entirely understood, there are several theories that have been proposed to explain how it occurs. They include the convergence theory and central centralization (see Chapter 14).

• Dental patients often have difficulty identifying the source of their pain including which tooth is affected. Additionally, they often experience referred orofacial pain and seek medical or dental attention for the referred pain rather than the dental pain.

• Most referred orofacial pain is of odontogenic origin; however, it can be caused by other disorders. The following conditions have been shown to produce referred pain in teeth:

  • TMD.

  • Myofascial pain.

  • Sinusitis.

  • Otitis media.

  • Muscle tension headaches.

  • Chronic neck problems.

  • Fibromyalgia.

  • Trigeminal neuralgia.

  • Cardiac disorders.

Neurovascular Origins of Orofacial Pain

Neurovascular disorders involving dilation or constriction of blood vessels can cause orofacial pain. These disorders usually affect the face rather than the oral cavity but can cause pain in both areas in certain circumstances. They are a heterogeneous group of disorders that share a common anatomic location (head) however; the etiologies are different and possibly multifactorial. In general, it is thought that in these disorders, the nociceptors associated with vessels in the head and dura become activated. Historically, they were described as “vascular pains” but is now fairly well accepted that it involves central and peripheral sensitization, at least in part.

• Migraines are severe, debilitating, typically unilateral, headaches thought to be caused by vasodilation of extracranial arteries or compression of the carotid or temporal arteries on the affected side. Symptoms can include auras, nausea, and photophobia. Ocular migraine sufferers may or may not display pain as seen in classic migraines. Both ocular and classical migraine sufferers with auras report seeing lights, zigzag lines, and stars or experience blind spots. Patients are commonly dysfunctional from their symptoms that can last for a period of minutes or hours to days.

• Migrainous neuralgias (cluster headaches) are less common than migraines but are more likely to cause orofacial pain. Males are more likely to be affected and generally present in middle age. Pain is unilateral, and occurs in “attacks,” often described as “burning.” The attacks can be very precise in intervals, occurring at the same time of day or night. Cluster headaches often localize around the eyes, sometimes causing conjunctivitis and rhinorrhea on the affected side. The etiology is not completely understood although vascular causes and the hypothalamus have been implicated.

• Temporal arteritis is an uncommon condition that produces severe headaches as well as myofascial pain. It is a systemic inflammatory vasculitis of unknown etiology. It most commonly involves the temple but can also present with a pattern following the facial or lingual artery. Symptoms include visual disturbances, headache, neck pain, facial pain, and fatigue. It is important to diagnose and treat this condition early as it can cause permanent blindness.

Neuralgias

• Neuralgias are a group of disorders that are caused by irritation or damage to a nerve. It is typically described as burning and/or stabbing pain that can occur anywhere in the body.

  • Trigeminal neuralgia is a chronic paroxysmal neuropathic disorder that produces intense and sometimes debilitating unilateral pain. Most often, it localizes to V2 and V3 of the trigeminal nerve (CN V), intraorally or extraorally or to both sites simultaneously. Trigeminal neuralgias are associated with trigger zones usually within the trigeminal nerve distribution pattern that sets off the attack. The length of the attack varies and can occur several times a day. There is often a period of remission that may last for extended periods of time.

    • The etiology is typically related to vascular compression; however, there are cases reported of nonvascular origins such as neoplasms (meningiomas and neuromas). If vascular compression has been identified as the cause, surgical decompression is usually very successful. More recently, ablative procedures such as the use of a gamma knife have shown some efficacy. Other than surgery, anticonvulsants are the treatment of choice.

  • Glossopharyngeal neuralgia is a fairly rare orofacial condition that follows the innervation pattern of the glossopharyngeal nerve (CN IX). Sites involved include nasopharynx, posterior aspect of the tongue, throat, tonsil, larynx, and ear. Glossopharyngeal neuralgia is a paroxysmal neuropathic disorder that can be triggered by mechanical stimulation of the trigger zone (oropharyngeal region) by swallowing, coughing, talking, and head movements.

    • Painful episodes may continue for months. There can also be periods of remission. Due to the close proximity of the glossopharyngeal and vagus nerves, episodic attacks may be associated with cardiac dysrhythmias.

    • Pharmacological treatment is similar to trigeminal neuralgias. Surgical intervention would involve decompression of the glossopharyngeal nerve.

  • Herpetic neuralgia is caused by reactivation of the herpes zoster virus (shingles) that can remain latent in the dorsal root ganglia of individuals who have previously contracted chicken pox.

    • The characteristic rash and ulcerations may be accompanied by neuralgia. The neuralgia may persist after the rash resolves.

    • Treatment includes antivirals, acetaminophen, ibuprofen, and topical antibiotics.