OBJECTIVE The aim of this study is to compare dental arch changes associated with different activation protocols of maxillary expander. METHODS A sample of 101 subjects with constricted maxillary arches (49 males and 52 females; mean age 10.96 ± 1.91 years) was enrolled in the study. All subjects underwent RME with a stainless steel banded expander cemented to the maxillary first molars and the expansion screw was randomly activated with two different rapid maxillary expansion protocols (one- quarter per day or two quarters per day). The study also involved a control group of 22 subjects (10 females and 12 males, mean age 10.39 ± 1.32 years) who underwent no treatment. A statistical comparison between the dental arch measures obtained before and after treatment in the two groups was performed. RESULTS The Wilcoxon rank-sum test shows statistically significant differences of the measurement increases between the two activation protocols (at least p=0.01). Statistically significant differences were also reported in comparison with the control group. CONCLUSIONS A faster activation protocol could be able to determine a greater anterior opening of the mid-palatal suture. Moreover, it seems to yield a higher width increase in the molar area.