Orthoses, screening kits, and associated devices, systems, and methods are disclosed herein. An orthosis (100) configured in accordance with a particular embodiment includes a left spacer (102) configured to be clenched between left lateral posterior teeth, a right spacer (104) configured to be clenched between right lateral posterior teeth, and a connector (106) extending therebetween. The connector is flexible to accommodate differences in relative positioning of left and right lateral posterior teeth in different patients. The orthosis, when operably positioned within an oral cavity of a patient, is configured to cause asymmetrical spacing between upper and lower posterior teeth relative to a sagittal plane. A screening kit configured in accordance with a particular embodiment includes sets of orthoses individually configured to cause different levels of asymmetrical or at least generally symmetrical spacing between upper and lower posterior teeth relative to the sagittal plane.
