Patients presenting to the general practitioner with pain of dental origin

The anatomy of a normal tooth is shown in Box 1, A. Caries extending from enamel into dentine usually causes some sensitivity and pain. The dentine consists of fine tubules that contain cellular processes and afferent nerve fibres surrounded by dentinal fluid. The “hydrodynamic theory” proposes that the fluid moves back and forth to stretch, compress, and excite the nerves in the pulp (the highly vascularised and innervated connective tissue in the central cavity of the tooth). For pain to be felt, the dentine must be excited by a noxious stimulus, either hot or cold, sweet or sour, or touch. The pain is best described as a sensation of sudden shock and is sharp in nature. It is never spontaneous in onset.2

As carious lesions progress, the pulp will eventually become inflamed. It has been postulated that pulpitis leads to increased intrapulp tissue pressure that irritates the sensory nerves of the pulp and causes pain.3 Early in the course of events, this inflammation is reversible and could be thought of as an exaggerated form of dentinal pain. Pain is felt in response to a stimulus (most commonly, cold), and the pain is mild to moderate.4

When the pulp is affected by caries, histological findings are moderate to severe inflammation and some areas of necrosis. Patients present with moderate to severe pain, and 90% report a history of pain before the present pain episode. The pain, in this case, may be triggered by a stimulus (commonly, heat) or arise spontaneously. This stage is identified as irreversible pulpitis, and endodontic treatment or extraction is indicated for the tooth.5

If the inflammatory process or infection is allowed to proceed, the pulp will accumulate more necrotic foci and infection will spread to the apical tissues. The initial pathological response is apical periodontitis (Box 1, B), which is associated with an acute form of periradicular pain that can be excruciating and sometimes lasts for days. The tooth is exquisitely painful to touch, and even contacting the tooth during mouth closure may bring a flood of tears. The pain has been described as constant (24 hours a day), gnawing, throbbing and pounding. Eventually, the patient may gain relief, only to bite on the tooth while eating or sleeping and start the pain cycle once more. Some patients beg to have the tooth extracted, but even if their wish is acceded to, pain may continue for another 48 hours owing to osteitis.4 Spread of infection into periapical tissues forms a localised infection or an abscess (Box 2, Case 1). This can spread to the bony periosteum and cause cellulitis or abscess of soft tissues of the face or neck, with potential life-threatening consequences through possible airway compromise or intracranial spread of infection.

Although caries is the most common cause of pulpitis and periapical spread of infection, there are other conditions that cause dentofacial pain. The most common are occlusal trauma, tooth fractures and cracks. Some infections are iatrogenic. GPs should be aware of caries as a cause of dental pain, but they should also be aware that not all carious lesions appear as cavities in teeth, particularly in this era of water fluoridation (Box 2, Case 2). Sometimes caries will show simply as an area of greyish discolouration or may only be visible on x-ray (Box 3).

Other causes of pain that are often missed by the GP are pericoronitis and alveolar osteitis (dry socket). The typical complaint of the patient with pericoronitis is severe, radiating pain in the back of the mouth and the inability to comfortably open or close the jaw. Not only is it painful to close against the inflamed operculum behind the erupting mandibular molar, but the pain of muscle trismus limits opening of the jaw as well. The soft tissues around the erupting molar are painful to touch, especially during eating (Box 4, Case 3).12

Dry socket, also known as acute alveolar osteitis, is an inflammatory condition of a dental extraction socket, occurring within 2–4 days of a tooth extraction (Box 4, Case 4). It is characterised by a severe, persistent throbbing pain from an extraction socket, which is usually empty but may contain a disintegrated blood clot and/or food debris. The bony walls of the socket are denuded and exquisitely sensitive to even gentle probing. Halitosis is invariably present. The condition probably arises from a complex interaction between surgical trauma, local bacterial infection and various systemic factors.13 Common risk factors are extraction of mandibular (but not maxillary) teeth (particularly lower third molars), poor oral hygiene, and smoking (especially if more than 20 cigarettes are smoked per day).14 Less common reasons for dentofacial pain include trigeminal neuralgia, atypical odontalgia and referred pain from temporomandibular disorders, salivary glands, sinuses and, rarely, the heart. Such unusual pains and presentations require specialist referral.

The main clinical points we have made in this article are summarised in the algorithm in Box 5.