Improved orthodontic appliances, along with related systems and methods, are provided. In one aspect, an appliance includes a shell having a plurality of cavities shaped to receive teeth, and a discontinuity formed in the shell. The appliance also includes an elastic member having a first portion directly coupled to the shell at a first attachment point and a second portion directly coupled to the shell at a second attachment point. The elastic member can be positioned to interact with the discontinuity.