Abstract
Eruption disturbances of maxillary central incisors are frequently caused by apical lesions of the predecessors after severe dental caries or traumatic injury, and the eruptive direction is often changed labio-palatally. Since the impacted central incisors will need to be extracted if serious root dilacerations occur due to late treatment, early traction is recommended after early detection. The erupted supernumeraries in the maxillary anterior region should be extracted as soon as possible because they inevitably induce the irregular alignment or impaction of the central incisor. Small odontomas the size of rice disturb the eruption of the incisor, even if their degree of radio-opacity is low. The latedeveloped germs of the lateral incisors sometimes produce eruption disturbances of the neighboring central incisor. As the late development of the lateral incisors may be related to the fusion of the predecessors, a careful examination is needed during the early mixed dentition period when fused primary teeth are detected in the maxillary anterior region.Eruption disturbances of maxillary canines are often induced by unidentified causes (nearly 75 %),and most affected canines incline mesially. The severity of the canine impaction can be estimated by the degree of overlap between the canine tip and the root of the lateral or central incisor. Although extraction of the predecessor will be effective in mild cases, traction will be needed in severe cases. Ectopic eruption of maxillary canines is sometimes caused by peg-shaped or congenitally absent lateral incisors because the affected canines lose the normal eruptive trail formed by the lateral incisor roots. Since most eruption disturbances of the maxillary canines occur unilaterally, it is important to palpate both sides to detect potential differences in the mobility of the primary canines or the labial gingival bulge before the eruption of the canine. When a difference is clearly noticed, it is critical to take radiographs.
