Orofacial Pain

A Guide for the Headache Physician

Martina K. Shephard, BDent(Hons), MBBS(Hons), FRACDS; E. Anne MacGregor, MD, FFSRH; Joanna M. Zakrzewska, MD, FDSRCS, FFPMRCA

Disclosures

Headache. 2014;54(1):22-39. 

In This Article

Types of Orofacial Pain

Dental Pain

There are few causes for dental pain; however, because of significant neural convergence in the jaws and face, it may be referred, poorly localized, or misdiagnosed. The 4 major causes of dental pain are pulpitis, cracked tooth syndrome, dental abscess, and dentine sensitivity.[13] These are often acute conditions, but because they are common, they may coexist with other chronic pains.[14]

Both the dental pulp and periodontal ligament contain nociceptors. Nociceptive output in these areas is triggered by changes in pressure and the effect of inflammatory mediators.

Pulpitis

Pulpitis is the term used to describe pain because of inflammation of the dental pulp, and it is usually due to dental caries. Inflammation of the pulp leads to accumulation of extracellular fluid, inflammatory mediator release, and vasodilatation, which causes an elevation of pressure within the pulp chamber, which is a non-compliant space. The pressure increases further as venous stasis and eventually pulp necrosis occur, with release of inflammatory mediators and necrotic cell contents. Elevated pressure and inflammatory chemicals activate nociceptors in the pulp chamber causing pain.

Reversible pulpitis is defined as a transient pain in response to specific stimuli (hot, cold, sweet), which occurs when the pulp is inflamed. These symptoms resolve when the cause of the inflammation is treated. The pain of reversible pulpitis may be described as fleeting, shooting, stabbing, or sensitive.

Irreversible pulpitis is characterized by spontaneous pain, which may be worsened by or persist following the removal of a stimulus such as heat or cold. It is an indicator of incipient pulpal necrosis. The pain of irreversible pulpitis is often described as persistent, throbbing, dull, or aching. It may be worsened by physical activity and head movement.

Pulpal pain is often poorly localized as the inflammation is restricted to the pulp chamber and is thus not affecting proprioceptive nerve fibers, which are located in the periodontal ligament. It is common for patients to be unable to localize the exact source of the pain. Pulpal pain may respond to simple or opioid-based analgesics, but the pain of irreversible pulpitis will not resolve until pulpal necrosis has occurred or the pulpal tissue has been mechanically removed (by endodontic treatment).

If pulpal inflammation and infection reaches the base of the pulp chamber, an area known as the apex or root tip, it may extrude through the apical foramen into the periodontal space (Fig. 2). This will cause pain due to stimulation of nociceptors in the periodontal ligament space, and the pain will be well localized due to involvement of periodontal ligament proprioceptive fibers. Extrusion of inflammatory fluid and necrotic cell products into the periodontal space causes pain because of pressure effects, and the tooth will become exquisitely tender to touch or biting. This leads to the pain becoming very well localized, and the source of pain may be readily identified by gentle tapping on the tooth. When inflammation and infection has progressed through the apical foramen, it is described as a periapical abscess.

Figure 2.

Dental anatomy.

Dental infection may progress into the bone, under the oral mucosa or into soft tissue spaces, and form an abscess or spreading infection, with resultant ongoing pain.

Cracked Tooth Syndrome

Cracked tooth syndrome occurs when a crack has occurred in the dental hard tissues and reaches the pulp chamber. The crack is usually not visible to the naked eye. Pain because of cracked tooth syndrome is classically intermittent, provoked on biting or releasing biting on a hard object, and is notoriously difficult to diagnose. It may be described as sharp or sensitive, and is usually related to mastication. The tooth may also become sensitive to hot and cold stimuli. It is thought that the pain is due to fluid shifts within the dentine tubules, which are generated due to pressure differences as the crack opens and closes during mastication. It can be extremely difficult to diagnose.[15]

Dentine Sensitivity

Pain because of dentine sensitivity is classically stimulated by exposure to cold, heat, sweet foods/drinks, and mechanical trauma such as toothbrushing. The sensation is due to the movement of fluid in dentinal tubules in response to osmotic or temperature-related effects. Dentinal tubules contain the processes of cells residing in the dental pulp (odontoblasts), and fluid movement appears to trigger nociceptive output by mechanisms that are as yet unclear. Gingival recession can lead to exposure of the endings of dentine tubules, as can loss of enamel on the crown of the tooth. Dentinal sensitivity is described as very rapid, fleeting, shooting pain, or sensitivity, and is always in response to an identifiable stimulus.

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