Dentoskeletal effects of a removable appliance for expansion of the maxillary arch: a postero-anterior cephalometric study

The aim of this study was to evaluate the dentoskeletal effects of early treatment in the primary or early mixed dentition with a removable appliance with expansion springs, assessed on postero-anterior (PA) cephalograms, in patients with a unilateral posterior crossbite when compared with untreated subjects. The treatment group consisted of 23 subjects, 8 males, and 15 females treated with a removable appliance for the expansion of the maxillary arch. The mean age at the start of expansion (T1) was 6 years 2 +/- 17 months, and 8 years +/- 18 months at the end of active therapy and after 1 year of retention (T2), with an observation interval of 22 +/- 7 months. The control group comprised 20 subjects (9 males and 11 females) with an untreated unilateral posterior crossbite. Their mean age was 5 years 9 +/- 15 months at the first observation and 7 years and 4 +/- 16 months at the second examination. The interval between the two observations was 18 +/- 7 months. Nine skeletal and two dental measurements on the transverse plane were assessed. The data from the two groups were compared by means of a Student's t-test for independent samples (P < 0.05). Positive dental and skeletal effects induced by the therapy were observed at T2. The width of the upper dental arch and that of the skeletal maxillary transverse dimension were significantly greater (P < 0.001) in the treatment group when compared with the controls.