RESUMO
The present study was conducted to evaluate the effects of modified Nance holding arch [tranpalatal arch soldered to Nance holding arch] as anchorage unit during canine retraction. Fourteen patients with Class I crowding sheared in this study. They were divided into two equal groups. All patients had orthodontic fixed appliance. In the first group, Nance holding arch was used for anchorage. On the other hand, a modified form of Nance holding arch [transpalatal arch soldered to Nance holding arch] was utilized for anchorage in the second group. Maxillary canines were retracted by power chain. For all patients cephalometric x-ray films and study casts were taken before and after canine's retraction. The results of this study revealed that; the modified Nance holding arch [transpalatal arch soldered to Nance holding arch] proved a very effective anchorage device. On the other hand, there was significant anchorage loss in the first group [Nance group] as there was mesial movement of the maxillary first permanent molars during canine's retraction. In addition there was no significant molar rotation in either group. Finally, the followings were concluded; the modified Nance holding arch provided an effective anchorage device than the Nance holding arch during canines retraction. Also, both Nance holding arch and the modified Nance form proved a very effective anchorage control against molar rotations during canines retraction