A healthy adult male patient presented himself, 11 days after a fixed orthodontic appliance was placed, with a sudden pink discoloration of the dental crown of tooth 21. The emergency dentist on call diagnosed the discoloration as non-painful peri-apical periodontitis, partly on the basis of a radiograph, and recommended endodontic treatment of tooth 21. Prior to endodontic treatment, the patient was first seen by the orthodontist who had initiated treatment. Tooth 21 was investigated and reacted normally to percussion and palpation but did not react to the cold test. The patient was referred to an endodontist who made the likely diagnosis: ‘Transient apical breakdown’. No endodontic treatment was carried out and the orthodontic treatment was not interrupted. Six weeks after the discoloration appeared, visible recovery was evident.