We investigated differences in the technical quality of root fillings according to socioeconomic status. In the Finnish Health 2000 Survey, which comprised a sample of 8,028 adults aged over 29 yr, 6,115 underwent panoramic radiography. A total of 7,986 endodontically treated teeth were detected among 3,095 participants. The criterion for a technically inadequate root filling was a distance from the root filling to the root apex of over 3 mm or a filling extruding beyond the apex. Educational level, employment status, and income were the measures of socioeconomic status. Differences in the frequency of inadequate root fillings according to socioeconomic status were investigated using a multilevel logistic mixed‐effects model taking into account age, gender, number of teeth, and type of root filled tooth. Almost half (46%) of the root fillings were inadequate. Among the over 64‐yr‐olds, higher education and higher income were associated with a higher probability of having an inadequate root filling. Among the under 65‐yr‐olds, socioeconomic status was not associated with root filling quality. Contrary to expectation, lower socioeconomic status was not associated with poorer endodontic treatment quality; however, higher income and higher education was associated with higher odds for inadequate root fillings among the over 64‐yr‐olds.