Abstract: The present invention relates generally to systems, devices, and methods for tracking compliance of orthodontic appliance usage, and more specifically to systems, devices, and methods for tracking compliance of orthodontic appliance usage using a compliance device and/or a light therapy apparatus. The invention provides compliances device that can be configured to be disposed within a patient's mouth. In some embodiments, the compliance device can comprise a sensor configured to detect an input associated with whether an orthodontic appliance is at least partially disposed within the patient's mouth at a first time and at a second time, with the second time being subsequent to the first time.