To establish prevalence and severity of external cervical resorption (ECR) in posterior teeth observed in bitewing (BW) radiographs in an epidemiological study of a 17-year-old patient population from community dentistry. Furthermore, to assess potential predisposing factors for ECR.

Posterior BWs from 5,596 patients (2,717 females, 2,879 males; mean age 17.8 years) were assessed by three observers in order to detect ECR (using Heithersay’s classification system, severity classes 1–4). When ECR was suspected, cone beam CT (CBCT) was offered to verify diagnosis. Prevalence was estimated based on ECR suspected in BWs and finally in CBCT. Possible predisposing factors (orthodontic treatment, trauma, and periodontal disease) were recorded and assessed for association with ECR.

In 41 patients, ECR was suspected in BWs (suspected prevalence 0.73%). Thirty-two patients accepted CBCT examination, of which eight were verified to have ECR (final prevalence 0.18%). In 24 patients, other disease entities and abnormal tooth morphology, that had mimicked ECR in BWs, excluded ECR in CBCT. ECR severity ranged from class 1–3 in BW and 2–4 in CBCT. All but one case had not been diagnosed by the patient’s community dentist. No statistically significant association between predisposing factors and ECR was identified.

ECR had low prevalence in this adolescent population, as observed in both BWs and CBCT. Still, early detection of ECR is important for treatment prognosis, and attention should be paid to this disease entity when assessing BWs obtained for other diagnostic purposes. CBCT may subsequently aid in verifying the disease.