With the use of pretreatment and posttreatment lateral cephalograms and study models, lip bumper therapy for two groups of 20 patients was evaluated. One group was treated with lip bumpers fabricated from stainless steel round wire covered with shrink tubing and activated every 2 to 3 months. The second group was treated with larger prefabricated lip bumpers covered with acrylic shields from canine to canine and activated every 4 to 5 weeks. Yearly rates of treatment change indicate that the type of lip bumper used and the method of clinical manipulation have no effect on mandibular incisor position. Both groups showed similar rates of controlled incisal tipping with the center of rotation at the apex. Dental movements of the posterior segment were significantly different between groups. The second group displayed significantly more molar tipping than the first group. The second group also showed significantly greater transverse expansion of the canines, first premolars, and first molars.