An example of RBL measurement in a periapical radiograph. RBL was calculated as the distance from the CEJ to the most coronal level of the alveolar crest (BL), where the periodontal ligament appeared with normal width. RBL was expressed as a percentage (%) of the total length of the root of the tooth, that is, CEJ to apex (A). BL, bone level; CEJ, cemento‐enamel junction; RBL, radiographic bone loss.