ODA stands for "Orthodontic Appliance". It refers to a dental appliance used in orthodontics, which is a branch of dentistry that deals with the study and treatment of malocclusions (improper bites), which can be caused by crowding or spacing of teeth, crookedness, overbite, underbite, or crossbite. An ODA may include devices such as braces, retainers, headgear, or other corrective appliances that are used to align and straighten teeth, improve bite, and create a more balanced facial structure.