牙痛是继续忍受还是提前做好防护?爱护牙齿，每天的必修课。
M:Sorry,I'm late.I was brushing my teeth. W:Brushing your teeth?Right before 'A Moment Of Science'? Why? M:I'm trying to get rid of a cavity. W:Get rid of a cavity?Are you stuck with a cavity once you have it? M:It depends on how deep it is.Acid from bacteria in your mouth can cause your tooth to decay.First, the acid eats away the very hard outer layer of your tooth, called the enamel. Inside the enamel is the dentin. It’s spongy and has nerve endings, so your tooth might be sensitive to sweets or cold if the decay reaches there.But the cavity doesn’t really start to hurt until it gets through the dentin to the soft pulp. That’s when you get a toothache. W:Oau！ M:Dentists will sometimes fix a cavity by putting in a filling while the decay is still in the enamel. But decay is reversible until it reaches the dentin. If it’s properly treated, the decay will stop, and the enamel will harden, although the tooth will never be perfect again. W:So that's why you're brushing.Can you do anything else to help get rid of a cavity? M:Dentists can also help by giving you a fluoride treatment, but you have to brush and floss regularly. You might have to give up soda and sweets.So it’s not easy–and dentists know that. That’s why they sometimes fill a cavity in its early stages, before it starts to hurt. W:So you’re not stuck with tooth decay once it happens.? M:No.But it’s better not to let it happen in the first place.