It is common knowledge for all dental personnel that root filled teeth can be painful. Earlier studies on this subject are meta-analyses and clinical studies reporting data in relation to the time since treatment was performed, not epidemiological studies reporting on the general population or cohorts who regularly attend dentistry. The studies often report ´all-cause tooth pain´ or´odontogenic´ versus ´non-odontogenic´ tooth pain. These are broad categories with different possibilities for the origins of pain. A better understanding of the possible origins of pain would aid in clinical assessment.

This doctoral thesis is centred around a cross-sectional clinical data collection in general dental practice and follow up of interventions monitored by collecting data from dental records over six years. The aim is to better understand painful root filled teeth better by exploring anamnestic, clinical, and radiographic characteristics at a regular check-up by the regular dentist.

Study I is an observational cross-sectional study. The aim was to investigate the frequency and characteristics of pain and discomfort, irrespective of origin, in a cohort of adult patients regularly attending the Public Dental Service in Sweden. A further aim was to examine whether there was an association between pain symptoms, clinical status and radiological findings. One out of ten participants experienced pain or discomfort from their root filled teeth; the average pain intensity was low. Lower age, tenderness to percussion and apical palpation were associated with painful teeth. Furthermore, 41.9% of the painful teeth had apical radiolucency.

Study II is a case-control study. Cases were participants with at least one painful root filled tooth, and controls were participants with a root filled tooth without pain. The aim was to compare, in detail, painful root filled teeth with root filledteeth without pain matched on age, sex, jaw- and tooth type, with the additional aim to explore patient- and tooth related factors that may explain the pain. It was more common with tenderness to percussion and apical palpation, as well as swelling, pocket depths greater than 6mm and apical radiolucency for the painful teeth. For 60% of the painful teeth, apical periodontitis was the likely origin of pain, marginal periodontitis and TMD were found to contribute in 30%, and for 10%, no obvious clinical or radiological findings could explain the pain.

In Study III, the painful teeth were subdivided into two groups: those with at least one sign of disease and those with no such signs. The aim was to compare painful root filled teeth with and without signs of inflammatory disease, regarding (i) pain characteristics, (ii) impact of pain and (iii) patient characteristics. No differences could be found except for higher pain intensity and no apical palpation of the teeth without signs of disease. The impact of pain was equally low, and there were no differences in patient characteristics.

In Study IV, all the participants from Study I who could be followed for six years were included, and the interventions were followed by collecting data from the dental records. The aim was to explore longitudinally what happens to root filled teeth in terms of interventions, regardless of time since RCT, during six years. A further aim was to explore how the interventions were associated with variables obtained from a standard clinical examination. Regarding the painful teeth, a third were extracted, another third had 'no event' recorded and, in falling order, the rest were 'scheduled for follow-up', had a 'new restoration' or were 'endodontically re- treated'. In comparison, it was more common with extraction and RCT for painful teeth than 'no event', 'scheduled for follow-up' and new restoration.

In conclusion, the findings indicate that pain from root filled teeth is a relatively common problem. Those with pain generally have a low intensity and minimal impact on everyday life. Apical periodontitis is the most common origin of pain, but a few are difficult to diagnose with the common examination modalities. The clinical presentation of teeth with and without signs of inflammation resemble each other, pointing to possible help from other diagnostic modalities. Even though extraction and RCT are more common interventions for painful teeth, not all painful teeth receive an intervention.