The overall goal of this thesis was to broaden our knowledge of chronic intraoral pain. The research questions were:•What methods can be used to differentiate inflammatory, odontogenic tooth pain from pain that presents as toothache but is non-odontogenic in origin?•What is the prognosis of chronic tooth pain of non-odontogenic origin, and which factors affect the prognosis?Atypical odontalgia (AO) is a relatively rare but severe and chronic pain condition affecting the dentoalveolar region. Recent research indicates that the origin is peripheral nerve damage: neuropathic pain. The condition presents as tooth pain and is challenging to dentists because it is difficult to distinguish from ordinary toothache due to inflammation or infection. AO is of interest to the pain community because it shares many characteristics with other chronic pain conditions, and pain perpetuation mechanisms are likely to be similar. An AO diagnosis is made after a comprehensive examination and assessment of patients’ self-reported characteristics: the pain history. Traditional dental diagnostic methods do not appear to suffice, since many patients report repeated care-seeking and numerous treatment efforts with little or no pain relief. Developing methods that are useful in the clinical setting is a prerequisite for a correct diagnosis and adequate treatment decisions.Quantitative sensory testing (QST) is used to assess sensory function on skin when nerve damage or disease is suspected. A variety of stimuli has been used to examine the percep¬tion of, for example, touch, temperature (painful and non-painful), vibration, pinprick pain, and pressure pain. To detect sensory abnormalities and nerve damage in the oral cavity, the same methods may be possible to use.Study I examined properties of thermal thresholds in and around the mouth in 30 pain-free subjects: the influence of measurement location and stimulation area size on threshold levels, and time variability of thresholds. Thresholds for cold, warmth and painful heat were measured in four intraoral and two extraoral sites. Measurements were repeated 3 times over 6 weeks, using four sizes of stimulation area (0.125–0.81 cm2). The threshold levels were highly dependent on location but less dependent on measuring probe size and time variability was small, and this knowledge is important for the interpretation of QST results.Study II applied a recently developed standardized QST examination protocol (intended for use on skin) inside the oral cavity. Two trained examiners evaluated 21 pain-free subjects on three occasions over 1–3 weeks, at four sites—three intraoral and one extraoral. Most tests had acceptable reliability and the original test instruments and techniques could be applied intraorally with only minor adjustments. Study III examined the value of cone-beam computed tomography (CBCT) in pain investigations. Twenty patients with AO and 5 with symptomatic apical periodontitis (inflammatory tooth pain) participated. The results indicate that when AO is suspected, addition of CBCT can improve the diagnostic certainty compared to sole use of periapical and panoramic radiographs, especially because of the superior ability of CBCT to exclude inflammation as the pain cause.Study IV assessed the long-term prognosis of AO, and analyzed potential outcome predictors.. A comprehensive questionnaire including validated and reliable instruments was used to gather data on patient and pain charac¬teristics and pain consequences from 37 patients in 2002 and 2009. Thirty-five percent of the patients reported substantial overall improvement at follow-up, but almost all still had pain of some degree after many years. The initial high level of emotional distress was unchanged. Low baseline pain intensity predicted improvement over time.