Three-dimensional assessment of the effects of extraction and nonextraction orthodontic treatment on the face

Abstract

The purpose of this prospective study was to compare the 3-dimensional (3-D) effects on the face of extraction and nonextraction orthodontic treatment in patients with skeletal Class I patterns. The sample of 24 patients included 12 whose treatment included extractions and 12 who were treated without extractions. Pretreatment study casts were assessed to evaluate dental differences between the 2 groups. Pretreatment and posttreatment lateral cephalograms and optical surface scans were also compared. In the lateral cephalometric assessment, the only significant (P <.05) pretreatment difference was lower lip length. Posttreatment, the nasolabial angle and lower lip thickness were significantly different (P <.05). Registration of the average 3-D optical surface scans indicated that, before treatment, the nonextraction group had longer and broader faces by 5 to 7 mm, and the upper lip and labiomental fold were 3 to 5 mm farther forward than in the extraction group. Posttreatment, the nonextraction group still had larger faces, but the difference was smaller. Faces in the extraction group became relatively more protrusive with treatment. The surface shape analysis technique showed that the cheeks were flatter in the nonextraction group at the start of treatment, but this reversed with time. In the extraction group, the concavity of the labiomental fold increased, while the nonextraction group showed no change in this area. The study demonstrates that 3-D optical surface scans offer more data for analysis compared with lateral cephalograms alone. It also highlights the changes that can be detected with surface shape analysis. (Am J Orthod Dentofacial Orthop 2002;121:244-56)