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Toothbrush is a tool used to clean mouth caity, But we usually ignore whether it is clean
or changed on time. This kind of toothbrush can remind us relace it on schedule in order
to reduce virus in the mouth.As the time that toothbrush is used goes by.,it becomes red
from the roots.After one and a half months, The whole toothbrush becomes red so that
it can remind us change toothbrush.
Hebei university of engineering
handan city, China