My grandmother lost all of her teeth during her life, and my parents lost many of theirs. They used to pop their dentures into a mug of whitener every night.
就连我自己的时代，牙齿脱落也是司空见惯的。我祖母所有的牙齿全部掉光，我父母也掉了绝大多数。他们每晚把假牙泡在装有增白剂的杯中。