expansion arch

ex·pan·sion arch

an orthodontic appliance that moves the dental structures distally, bucally, or labially, creating increased molar to molar width and arch length.

ex·pan·sion arch

(eks-panshŭn ahrch)
Orthodontic appliance that moves dental structures distally, bucally, or labially, creating increased molar-to-molar width and arch length.