Long-term effects of rapid maxillary expansion: a posteroanterior cephalometric evaluation

The aim of this study was to investigate long-term effects induced by rapid maxillary expansion (RME), followed by comprehensive orthodontic treatment, in a sample of 42 patients compared with normal growth changes in a sample of 20 subjects. Treated subjects underwent Haas-type RME with 2 turns a day (0.25 mm per turn) until the expansion screw reached 10.5 mm (about 21 days). The Haas expander was kept on the teeth as a passive retainer for an average of about 2 months. Immediately after the Haas expander was removed, fixed standard edgewise appliances were placed. Posteroanterior cephalograms were analyzed for each subject in both groups at T1 (pretreatment) and at T2 (long-term observation). The mean age at T1 was 11 years 10 months for both the treated and the control groups. The mean ages at T2 also were comparable (20 years 6 months for the treated group, and 17 years 8 months for the control group). The study included transverse measurements on dentoalveolar structures, maxillary and mandibular bony bases, and other craniofacial regions (nasal, zygomatic, orbital, and cranial). RME followed by edgewise appliance therapy appears to be an effective procedure to increase transverse facial dimensions in the long term, at both the skeletal and the dentoalveolar levels. Significant pretreatment deficiencies in maxillary width, maxillary incisor apex width, and maxillary first molar width remained corrected at a mean age of about 20 years. The initial deficiency in lateroorbital width was also eliminated.