<p>Transient apical breakdown (TAB) may occur during pulp repair after dental traumatic injury, including orthodontic force. Herein, we describe TAB in the maxillary right central incisor of a 24-year-old woman during orthodontic treatment for a severe gummy smile. Eight months after initiating intrusion of the maxillary anterior teeth using temporary anchorage devices, the maxillary right central incisor showed discoloration and was non-responsive to electric pulp tests. The orthodontic force on the maxillary anterior teeth was immediately removed, and loxoprofen sodium, a non-steroidal anti-inflammatory drug (NSAID), was administered three times a day for seven days. Six months after removal of the orthodontic force, the crown colour improved and the tooth regained sensitivity to electric pulp testing. Therefore, orthodontic treatment was resumed and was completed two years after initiation. Obliteration of the root canal of the maxillary right central incisor was observed during a four-year-retention period. The findings in this case suggest that removal of orthodontic force and administration of NSAIDs are possibly useful for improving TAB following traumatic pulp injury due to orthodontic treatment.</p>