| abstract |
This invention is directed to a plastic orthodontic appliance having projections extending outwardly from a bonding base. The projections include broadened outer extremities and undercuts proximate the outer extremities which form mechanical bonds with a bonding adhesive. The projections have peened free ends that form the undercuts, preferably with minute fractures therein extending into the outer extremities of the projections. In one application, a plurality of appliances in the form of slotted brackets is provided for cooperating with an archwire to apply corrective forces to a patient's teeth on which the brackets are mounted. Another aspect of the invention concerns a method of making plastic orthodontic appliances suitable for mechanical bonding. The method includes molding a plastic orthodontic appliance having projections with undeformed outer ends or tips and subsequently bombarding the tips of the projections with particles impinged thereon, for example as by peening, to widen the outer extremities of the projections to form the undercuts. In the preferred embodiment of the method, ANSI no. 2 glass beads are fluidized and blown in an air stream onto the tips of the projections to widen and fracture the end regions of the projections, providing the surface with a characteristically peened texture, preferably one that includes fractures into the end regions. |