Introduction: Maxillary transverse discrepancies are commonly treated with a rapid maxillary expander (RME) with the intention of obtaining skeletal expansion to widen the maxilla. However, as patients become older/skeletally mature, obtaining successful suture separation becomes less likely. This could lead to a potential surgery to correct the transverse discrepancy. Temporary anchorage devices (TADs)/mini-screws/micro-implants) are becoming more popular and are being incorporated into the appliance designs of RMEs in order to increase the skeletal anchorage. Research has shown these TAD-supported RMEs, which may also be called MARPEs (mini-screw assisted rapid palatal expanders), MARMEs (mini-screw assisted rapid maxillary expanders), or MSEs (maxillary skeletal expanders), can be an effective option for achieving skeletal expansion for patients who are older/more skeletally mature. There are a variety of appliance designs (tooth-borne, tooth-bone borne, and bone-borne) as well as variations within the specific designs of each appliance. The purpose of this study was to evaluate the dentoalveolar effects of traditional RMEs versus TAD-supported RMEs. Methods: 48 subjects who were treated with rapid maxillary expansion and had a successful split of the midpalatal suture (MPS) were included. They were treated at the University of Iowa Orthodontic Department. 19 subjects were treated with a TAD-supported RME and 29 were treated with a traditional (2-banded) RME. Pre- and post-expansion measurements including arch perimeter, tooth size, intercanine width, intermolar width, arch length, inclination of alveolus, and inclination of molar were made on maxillary digital models. Crowding was determined by calculating the difference of arch perimeter and the sum of the mesial-distal tooth widths (arch perimeter-tooth size). Results: When comparing differences in pre- and post-expansion measurements in subjects with traditional RMEs, mean arch length, absolute mean crowding, and mean inclination of molars were significantly higher at pre-expansion. The mean arch perimeter, mean tooth size, mean intercanine width, mean intermolar width, and mean inclination of alveolus were significantly higher at post-expansion. The same categorical findings were found in pre- and post-expansion measurements in subjects with TAD-supported RMEs. When comparing the change in pre- and post-expansion measurements between subjects with traditional RMEs and TAD-supported RMEs, no statistically significant differences between the two groups were found for mean changes in arch perimeter, tooth size, crowding, intermolar width, inclination of alveolus, and inclination of molars. However, the mean change (increase) in intercanine width in the TAD-supported RME group was significantly higher than in the traditional RME group. In addition, the mean absolute change in arch length (a larger decrease in arch length) was significantly higher in the TAD-supported RME group. Conclusion: Both traditional and TAD-supported RMEs can lead to significant changes during expansion. We found TAD-supported RMEs to have a greater increase in intercanine width and a larger decrease in arch length versus traditional RMEs. This should be carefully interpreted as there are many variables involved that could contribute to this conclusion.