self-treatments using baking soda, ash and hydrogen peroxide provided online with no dental experience, can strip tooth enamel and cause lasting damage to the gums, experts cautioned。

　　专家提醒，网上流传的用苏打粉、灰末和过氧化氢进行牙齿美白的方法，若没有牙医的指导，会损伤牙釉质，给牙齿带来永久的伤害。

　　the techniques are becoming an increasingly popular alternative to expensive professional treatment, especially among teenage girls。

　　目前这些美白方法广受欢迎，尤其是受到少女们的追捧，并逐渐取代了昂贵的专业美白治疗。

　　but dentists said some of the methods can erode the enamel covering of the teeth, making them appear darker rather than whiter。

　　但牙医提醒说，有些方法可能会损伤覆盖在牙齿上的牙釉质，反而让牙齿显得更黑。

　　up to 100,000 people undergo some type of teeth whitening treatment each year, ten times more than did so five years ago。

　　近年来，每年进行牙齿美白的人数已经达到10万人，是五年前的十倍。

　　but for many people the process is prohibitively expensive, costing up to ￡1,300(＄2,096) for laser treatment and as much as ￡700(＄1,128) for professional bleaching。

　　但是对于很多人来说，进行专业牙齿美白的费用太过高昂。激光美白的费用是1300英镑(约2096美元)，专业牙齿漂白至少需要700英镑(约1128美元)。

　　professor andrew eder, clinical director of the london tooth whitening centre, said using baking soda repeatedly would strip the teeth of enamel, leaving them browner and more sensitive, while salt would scratch the enamel and any use of acid was especially damaging。

　　伦敦牙齿美白中心临床主任安德鲁 埃德尔教授表示，反复使用小苏打会损害牙釉质，牙齿会变得越发暗沉、敏感；用盐可能会刮伤牙釉质；而使用任何盐酸美白牙齿带来的伤害则更大。