Mandibular arch dimensions following bonded and banded rapid maxillary expansion

BackgroundThe purpose of this study was to examine changes in mandibular arch dimensions of subjects submitted to either bonded or banded maxillary expansion.MethodsThe sample comprised of two groups, one with patients who underwent maxillary expansion with banded, Haas-type expanders, retrospectively selected (banded group), and the other patients carefully matched in sex, age, and malocclusion, prospectively observed with bonded, Hyrax-type expanders (bonded group). Each group was composed of 29 subjects evaluated at T1, before maxillary expansion, and T2, after expansion and stabilization. The mandibular arches were evaluated for changes in arch width, depth, and perimeter. Paired and independent Student's t tests were used to compare groups.ResultsPatients in the banded group experienced significantly more mandibular arch width expansion in the molar region. Both groups experienced a decrease in arch depth; however, the bonded group showed significantly greater loss.ConclusionRapid maxillary expansion is an effective method for achieving a gain in arch width and space in the maxillary arch and, depending on the type of expander, banded or bonded, it produces a different response on an untreated mandibular arch.