An orthodontic device a base having a central longitudinal plane and a plurality of posts extending relative to the base. In one aspect, the posts are positioned with a first subset of at least one post on one side of the central longitudinal plane and a second subset of at least one post positioned on the opposite side of the central longitudinal plane such that facing first surfaces define a first slot with a first width and facing second surfaces define a second slot above the first slot with a second width larger than the first width and wherein a passage defined from the second slot to the first slot. In another aspect, the posts are angled relative to the base such that the posts converge as they approach the base.
