Tooth attachments are provided comprising one or more convex surfaces for engagement by a surface of an orthodontic appliance. Polymeric shell appliances are provided in which the polymeric shell appliances are configured to provide one or more activation forces to facilitate tooth movement. The polymeric shell appliances may comprise one or more tooth receiving cavities. The polymeric shell appliances may further comprise an engagement portion with a surface configured to engage a convex attachment surface in order to apply a tooth moving force.
