Aim To assess the prevalence of apical periodontitis (AP) and the technical quality of root canal treatment in an adult sub-population in London.

Methodology Panoramic radiographs of 136 patients who attended a dental hospital were collected. The periapical health of teeth present was assessed radiographically and the presence or absence of AP noted. The technical quality of the root canal treatment was scored as adequate or inadequate, based on the European Society of Endodontology (2006) guidelines.

Results A total of 3,396 teeth were assessed; AP was detected in 4.1% of the teeth. Forty-nine percent of patients had at least one tooth with radiographic evidence of AP. The percentage of root filled teeth with AP was 38.3%. AP was significantly more frequently found in root treated, compared with non-root treated, teeth (p <0.001). In 44.3% of the cases, the technical quality of the root canal filling was inadequate. AP was detected in 14% of adequately, compared with 68.6% of inadequately, root filled teeth. There is a significant negative correlation between the technical quality of root canal treatment and the presence of AP (p <0.001).

Conclusions There was a high prevalence of AP and poor technical quality root canal treatment; a strong association between AP and root filled teeth, and between the periapical health and the technical quality of the root canal treatment. The results are consistent with previous studies using similar methodology and re-confirmed that high technical quality root canal treatment is crucial to ensure a favourable treatment outcome.