The effect of a lip bumper on lower dental arch dimensions and tooth positions.

The effect of a lip bumper on the dimensions of the lower dental arch and on the inclination of the incisors and first molars was studied in 40 children, aged 9-12 years. The children wore their lip bumper full time for 7-10 months. The effects of the lip bumper therapy were recorded on dental casts and profile cephalograms made before and after the treatment. The positions and stages of development of the lower second molars were determined on pretreatment intra-oral radiographs. The lip bumper treatment resulted in an increase of the dental arch widths between the molars, premolars, and canines. The arch length increased through proclination of the incisors and uprighting of the first molars. The stages of development and the positions of the second molars had no influence on the effect of the treatment. Simultaneous treatment in the maxilla with a headgear, a transpalatal arch or a removable plate had no influence on the outcome of the lip bumper therapy.