Subsequent Expansion in the Mandibular Intercanine Distance with Rapid Maxillary Expansion

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. Dental casts were measured from nineteen subjects at four time-points. 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. There was significant increase in mandibular intercanine width as well as incisor alignment from expansion treatment. 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.