Apical root resorption is a biological process induced when orthodontic force is exerted on a tooth and local necrosis of the periodontal ligament occurs. Macrophages remove the necrotic tissue. In this way, differentiating osteoclasts can both attach to the now available dental surface and can then provoke root resorption. There is considerable uncertainty among dental practitioners on how to deal with clinically relevant apical root resorption (≥2 mm) during or after orthodontic treatment. To increase understanding and to improve the quality of care, the Dutch Association of Orthodontists has developed a clinical practice guideline. Recommendations have been formulated for the diagnosis of apical root resorption, possible risk factors and treatment management in order to respond adequately to this problem in practice.