The aim of this study was to investigate the quality of endodontic and coronal restorations and the association with periapical status in a Danish population.

A total of 614 randomly selected individuals (20–60+ years of age) from Aarhus County had a full‐mouth radiographic examination. The quality of endodontic and coronal restorations and the periapical status of endodontically treated teeth were assessed by radiographic criteria. Root fillings were categorized as ‘adequate’ or ‘inadequate’ with regard to root filling length and lateral seal. Coronal restorations were categorized into ‘adequate’ and ‘inadequate’, defined by the absence or presence of radiographic signs of overhangs or open margins. Results were analysed statistically using the chi‐squared test.

The total number of endodontically treated teeth was 773, and 52.3% had apical periodontitis (AP). Root‐filled teeth with an adequate lateral seal had a lower incidence of AP than teeth with an inadequate seal (44.3% vs. 57.8%), and teeth with an adequate root filling length were associated with a better periapical status than teeth with inadequate length of the root filling (42.0% vs. 67.6%). Similarly, adequate coronal restorations were associated with better periapical status than inadequate restorations (48.0% vs. 63.9%). When both root filling and coronal restoration quality were assessed, the incidence of AP ranged from 31.2% (optimal quality) to 78.3% (all parameters scored as inadequate).

Inadequate root canal and coronal restorations were associated with an increased incidence of AP.