LONG-TERM STABILITY OF RAPID PALATAL EXPANDER TREATMENT AND EDGEWISE MECHANOTHERAPY

Previous studies on long-term stability of orthodontic treatment prima rily have focused on the stability of the lower arch treated with edge wise appliances. The aim of this study was to evaluate the long-term s tability of the upper and the lower dental arches of patients treated with a rapid palatal expander. The sample comprised of 165 dental cast s randomly selected from patients who had been out of retention for 8 to 10 years at a mean age of 30 years. Measurements were made directly on dental casts obtained at the three time intervals: before treatmen t, after treatment, and after retention. Differences over time between the upper and the lower dental arches and between intervals were anal yzed by a two-way multivariate analysis of variance (MANOVA) and post hoc Bonferroni t tests. Differences between after treatment and after retention were statistically significant (P < 0.006) for all except lo wer intermolar width. However, only for lower and upper arch lengths a nd perimeters were the differences greater than 2.0 mm. Treatment with the rapid palatal expander presented good stability for upper interca nine width, upper and lower intermolar widths and incisor irregularity . Lower intercanine, arch length, and perimeter presented poor stabili ty.