Figure 1From: Apical root resorption during orthodontic treatment with aligners? A retrospective radiometric study Measurement of the panoramic radiographs: root and crown lengths and the calculation-formula for the relative change of the root-crown-ratio (RCR) during orthodontic treatment: post-treatment RCR relative to pre-treatment RCR (rRCR) in percentage; (CEJ = cemento-enamel junction)[7, 10]. Back to article page