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tooth decay; decayed tooth; dental cavity; dental caries
むし歯が痛くて夜眠れなかった。
The cavity hurt so much I couldn't sleep at night.
甘いものを食べすぎてむし歯になった。
I got a cavity from eating too many sweets.
子供のむし歯を防ぐために歯磨きを教える。
I teach my child to brush to prevent cavities.