Apparatuses (e.g., systems and devices, including dental appliances and series of dental appliances) that may include one or more conversion appliances that may be worn on a subject’s during a treatment plan without applying substantial orthodontic forces on the subject’s teeth. The conversion appliances described herein may be configured to provide the user with a similar feel as a dental appliance. In some cases these appliances are not part of the dental treatment plan but are added between one or more stages. The dental professional may include one or more conversion appliances between one or more stages of a dental treatment plan, and conversion appliances may be added after the dental treatment plan has been finalized.