| A study of the short-term and long-term effects of rapid maxillary expansion on the mandibular anterior teeth was carried out using a retrospective approach. The patient records of 19 patients that met the inclusion criteria were isolated from a pool of 400 who had the treatment. The patients were selected according to dental development so that they were not expected to have an increase in mandibular intercanine distance due to growth.;Dental casts were measured at four time-points: initiation of treatment, expander stabilization or removal, the end of treatment, and an average of over eight years after retention was discontinued. Changes in mandibular canine width and incisor crowding with no lower treatment during the expansion period, with fixed appliance therapy, and after retention were examined. The changes during expansion and after retention were tested for correlation to age, duration of expansion treatment, and amount of maxillary expansion. Long-term stability of the orthodontic result was also examined.;There was significant spontaneous increase in mandibular intercanine width as well as spontaneous incisor alignment from expansion treatment. There was also significant relapse long-term of the width gained in treatment, but the relapse was to an acceptable extent and was not beyond the spontaneously expanded distance. No significant correlations were noted between age, duration of expansion, or amount of expansion versus the changes in the lower anterior teeth in the short or long term with the treatment. The mandibular incisor alignment remained stable long-term. |
