OBJECTIVETo investigate the root length of posterior teeth after palatal expansion by magnetic expansion appliance.

METHODSA total of 32 patients who accepted palatal expansion with magnetic expansion appliance were enrolled in the study. Pretreatment and post-treatment cone-beam computed tomography (CBCT) images were obtained. A paired t test was used to evaluate the length change, and a group t test was used to compare the tooth lengths of developing and developed teeth.

RESULTSAnchorage teeth showed greater root resorption than non-anchorage teeth, whereas the developed posterior teeth showed reduced resorption. Moreover, the mesial buccal roots of the first molar and first premolar were reduced. No resorption was found in the developing teeth group.

CONCLUSIONThe magnetic palatal expansion can reduce the root length, particularly of developed root. The developing root of anchorage teeth show greater tolerance to resorption than the developed root. Early palatal expansion treatment with magnetic expansion appliance can reduce the risk of root resorption.