Rapid maxillary expansion in early-mixed dentition: effectiveness of increasing arch dimension with anchorage on...

To assess the effectiveness of a Haas expander anchored to deciduous teeth in changing dental arch dimension and improving crowding and to evaluate stability of changes until permanent dentition.

closed cohort retrospective and case-control study. Eighteen patients undergoing early treatment for lateral crossbite (mean age 7.6 yrs; SD 1.0) at two practices located in La Spezia and Massa (Italy) were analysed. The treated group was compared with 72 control subjects divided into: 32 untreated adolescents with and without lateral crossbite and the same canine dental class as treated patients before expansion (Class II Division 2), 18 adults and 18 adolescents with dental Class I. All groups were matched for gender (ratio males:females, 8:10). The dental casts images of treated patients were digitally measured before and after treatment, and in permanent dentition. Patients at the last follow-up were compared with control subjects.

In treated patients the increase in intermolar width and the improvement in anterior crowding were significant and stable until adolescence. Untreated adolescents with lateral crossbite showed the narrowest transversal widths and the highest irregularity. No difference was found among treated patients, adolescents without lateral crossbite, and adolescents and adults with a normal occlusion.

The Haas expander anchored on deciduous teeth is effective in improving dental arch constriction and crowding in patients treated for lateral crossbite. The result is stable until permanent dentition. In absence of treatment, constriction of dental arch may persist, with a higher level of irregularity.