[The effect of modified Nance arch on treating maxillary impacted canine transposed with first premolar].

PURPOSE: To explore the effect of modified Nance arch on treating maxillary canine-first premolar transposition cases, in which the anchorage and force direction were discussed. METHODS: Modified Nance arch was applied to 5 cases with maxillary impacted canine-first premolar transposition. First, a lingual knot button was bonded on the surface of the canine crown. Modified Nance arch was decorated with a hook that moved horizontally and buccally. Then the location of the hook was gradually adjusted in order to move the canine cross the root of the first premolar and move the canine to the right position. At last the canine was moved downward by straight wire appliance. RESULTS: Five maxillary transposed canines were fully erupted in their right position, with normal pulp activity and gingival morphology. No obvious root resorption was detected. The mean treatment time was 30 months. CONCLUSIONS: Modified Nance arch has advantages in treating canine-first premolar transposition.