Canker sores are common, shallow ulcers that appear inside the mouth for a variety of reasons such as changes in diet, hormones, injury and stress. They are painful, but they usually go away on their own and are not contagious.

Kids who wear removable retainers must take them out to eat, and with the socializing and distractions of a school lunchroom, we’d probably forget them at least once ourselves. Many of them are also clear, which looks nice for a smile, but makes them hard to find on trays, countertops, etc.