Evaluation of immediate soft tissue changes after rapid maxillary expansion

objective: to evaluate immediate soft tissue changes following rapid maxillary expansion (rme) in growing patients, using cone beam computed tomography (cbct). methods: twenty-three consecutive patients (10 male, 13 female) treated by rme were selected. patients were scanned using cbct prior to placement of the rapid maxillary expander (t0), then immediately following full activation of the appliance (t1). defined landmarks were then located on the pre- and post-treatment orientated images. change in landmark position from pre- to post-treatment was then measured. in addition to landmarks, 10 direct measures were made to determine distance change without regard to direction to measure soft tissue change of the lips. results: significant transverse expansion was measured on most soft tissue landmark locations. all the measures made showed significant change in the lip position with a lengthening of the vertical dimension of the upper lip, and a generalized decrease of anterior-posterior thickness of both the upper and lower lips. conclusions: significant changes in the soft tissue do occur with rme treatment. there is a transverse widening of the midface, and a thinning of the lips.