The aim of this retrospective study in mixed dentition was to quantify dental arches and radiographic changes with a rapid maxillary expander followed by a transpalatal bar with arms and a 3D Quad action mandibular appliance, at the end of the treatment (T1) and six months afterwards (T2).
Material and methods: Thirty Class II patients in mixed dentition with tooth size-arch length discrepancies were studied (22 treated). We obtained measurements from dental casts before treatment, at T1 and T2 and radiographic changes at T1. The breathing was appraised.
Results: We found a significant (p < 0.05) increase of maxillary (+7.41 mm) and mandibular (+2.96 mm) dental arch perimeter, of intercanine gingival width (maxillary +3.25 mm, mandibular +1.57 mm) and of intermolar gingival width (maxillary +5.32 mm, mandibular +2.32 mm). There is a statistically significant increase of SNB angle. All posterior cross bites were corrected. We obtained a better position for the maxillary canine on radiography. All patients had nasal breathing at T1. Non treated subjects showed no improvement. In conclusion, this interceptive treatment corrected posterior cross bites, improved breathing and suggests an amelioration of tooth size-arch length discrepancy.