brush – v. to clean something with a brush—a tool with many stiff hairs or fibers used to clean or smooth

participant – n. a person who is involved in an activity or event

inflammation – n. a condition in which a part of your body becomes red, swollen, and painful

causation – n. the act or process of causing something to happen

association – n. a connection or relationship between things or people

fluoride – n. a chemical that is sometimes added to drinking water and toothpaste to help keep teeth healthy