Toothache may be caused by dental conditions (such as those involving the dentin-pulp complex or periodontium), or by non-dental (non-odontogenic) conditions. There are many possible non-dental causes, but the vast majority of toothache is dental in origin.
Both the pulp and periodontal ligament have pain receptors, but the pulp lacks proprioceptors (motion or position receptors) and mechanoreceptors (mechanical pressure receptors). Consequently, pain originating from the dentin-pulp complex tends to be poorly localized, whereas pain from the periodontal ligament will typically be well localized, although not always.
For instance, the periodontal ligament can detect the pressure exerted when biting on something smaller than a grain of sand (10-30 µm). When a tooth is intentionally stimulated, about 33% of people can correctly identify the tooth, and about 20% cannot narrow the stimulus location down to a group of three teeth. Another typical difference between pulpal and periodontal pain is that the latter is not usually made worse by thermal stimuli.
The diagnosis of toothache can be challenging, not only because the list of potential causes is extensive, but also because dental pain may be extremely variable, and pain can be referred to and from the teeth. Dental pain can simulate virtually any facial pain syndrome. However, the vast majority of toothache is caused by dental, rather than non-dental, sources. Consequently, the saying “horses, not zebras” has been applied to the differential diagnosis of orofacial pain. That is, everyday dental causes (such as pulpitis) should always be considered before unusual, non-dental causes (such as myocardial infarction). In the wider context of orofacial pain, all cases of orofacial pain may be considered as having a dental origin until proven otherwise. The diagnostic approach for toothache is generally carried out in the following sequence: history, followed by examination, and investigations. All this information is then collated and used to build a clinical picture, and a differential diagnosis can be carried out.
The chief complaint, and the onset of the complaint, are usually important in the diagnosis of toothache. For example, the key distinction between reversible and irreversible pulpitis is given in the history, such as pain following a stimulus in the former, and lingering pain following a stimulus and spontaneous pain in the latter. History is also important in recent filling or other dental treatment, and trauma to the teeth. Based on the most common causes of toothache (dentin hypersensitivity, periodontitis, and pulpitis), the key indicators become localization of the pain (whether the pain is perceived as originating in a specific tooth), thermal sensitivity, pain on biting, spontaneity of the pain, and factors that make the pain worse. The various qualities of the toothache, such as the effect of biting and chewing on the pain, the effect of thermal stimuli, and the effect of the pain on sleep, are verbally established by the clinician, usually in a systematic fashion, such as using the Socrates pain assessment method (see table).
From the history, indicators of pulpal, periodontal, a combination of both, or non-dental causes can be observed. Periodontal pain is frequently localized to a particular tooth, which is made much worse by biting on the tooth, sudden in onset, and associated with bleeding and pain when brushing. More than one factor may be involved in the toothache. For example, a pulpal abscess (which is typically severe, spontaneous and localized) can cause periapical periodontitis. Cracked tooth syndrome may also cause a combination of symptoms. Lateral periodontitis (which is usually without any thermal sensitivity and sensitive to biting) can cause pulpitis and the tooth becomes sensitive to cold.
Non-dental sources of pain often cause multiple teeth to hurt and have an epicenter that is either above or below the jaws. For instance, cardiac pain (which can make the bottom teeth hurt) usually radiates up from the chest and neck, and sinusitis (which can make the back top teeth hurt) is worsened by bending over. As all of these conditions may mimic toothache, it is possible that dental treatment, such as fillings, root canal treatment, or tooth extraction may be carried out unnecessarily by dentists in an attempt to relieve the individual’s pain, and as a result the correct diagnosis is delayed. A hallmark is that there is no obvious dental cause, and signs and symptoms elsewhere in the body may be present. As migraines are typically present for many years, the diagnosis is easier to make. Often the character of the pain is the differentiator between dental and non-dental pain.
Irreversible pulpitis progresses to pulp necrosis, wherein the nerves are non-functional, and a pain-free period following the severe pain of irreversible pulpitis may be experienced. However, it is common for irreversible pulpitis to progress to apical periodontitis, including an acute apical abscess, without treatment. As irreversible pulpitis generates an apical abscess, the character of the toothache may simply change without any pain-free period. For instance, the pain becomes well localized, and biting on the tooth becomes painful. Hot drinks can make the tooth feel worse because they expand the gases and likewise, cold can make it feel better, thus some will sip cold water.