ABSTRACT
The effect of slow maxillary expansion by removable appliances on mandibular arch width during mixed dentition. This was a clinical trail study containing two groups. The experimental group included 20 patients with posterior cross bite and the mean age of 8.5 and the control group had 10 subjects with the mean age of 8.7 years. Maxillary removable expansion devices were prescribed in the first group but the control group did not receive any kind of expansion treatment. Study models were prepared before and following 8-12 months after treatment. Lower arch widths were measured in three areas [canine, first and second premolar region] in each phase. The arch widths in two phases were compared in each group by paired t-test. In the expansion group, lower arch width increased significantly in the canine and first premolar region [P < 0.001]. In non-expansion group no significant difference in lower arch widths was detected after treatment. Slow maxillary expansion by means of removable appliances significantly increases lower arch width in canine and first premolar region