Objective
Compare changes in arch form after RME achieved by Expander with Differential Opening (EDO), Hyrax‐type and Haas‐type expanders.
Materials and Methods
Dental models were obtained from 61 patients aged 7‐11 years before expansion (T1) and 6 months after the active phase when the appliances were removed (T2). The groups were formed according to the expander used: EDO (n = 18, mean age: 9.46 ± 0.82 years), Hyrax‐type (n = 22, mean age: 9.62 ± 1.57 years) and Haas‐type (n = 21, mean age: 9.29 ± 1.05 years). The expander`s activation protocol consisted of 7 mm, except for EDO`s anterior screw, which was 9 mm. The measurements of upper and lower intercanine distance, inter‐first permanent molar, arch perimeter and length, maxillary canine and first‐permanent molar inclination, and palatal depth were performed using the OrthoAnalyzer 3D software. Intergroup comparisons of T1 and between changes (T2‐T1) were performed using ANOVA followed by Tukey.
Results
In the upper intercanine distance EDO provided a greater increase than Haas‐type. In the distance between upper fist permanent molars EDO showed higher values than Haas‐type and Hyrax‐type. In the lower intercanine distance and maxillary arch length, Haas‐type promoted higher increase than EDO.
Conclusions
The EDO promoted greater transverse changes in anterior region than Haas‐type and greater transverse changes in posterior region of the maxilla than both conventional expanders. The appliance used for RME influences dental arch changes after treatment; therefore, it is recommended to individualize the choice of expander depending on the clinical necessity of each case.