文/路易丝·邦德 译/付迎杰 常海潮

You may long for a whiter smile, but are teeth naturally yellow? In a world where tooth whitening is increasingly common, especially among those in the public eye, it can be easy to forget what natural teeth look like.A study showed that up to 61% of Americans wish they could change the appearance of their teeth with a lack of whiteness coming out on top.

你可能渴望笑起来的时候牙齿显得更白，但牙齿天然就是黄色的吗？牙齿美白越来越普遍，尤其是在公众人物当中，在这样的形势下，我们很容易忘记牙齿天然的样子。一项调研表明，多达61%的美国人希望改变牙齿的外观，嫌牙齿不够白位居榜首。

2Despite many Americans having concerns about the appearance of their teeth, the average person only brushes their teeth for 45 to 70 seconds a day in findings from the Academy of General Dentistry.Experts recommend brushing teeth twice a day for two minutes.Maintaining good oral hygiene is an important factor in the appearance of your teeth.

2尽管许多美国人在意他们的牙齿外观，但全科牙医学会的调查结果显示，一股人每天只刷牙45 到70 秒。专家建议每天刷牙两次，每次刷两分钟。保持良好的口腔卫生是影响牙齿外观的一个重要因素。

3In this article, we will dive into the science behind the color of our teeth.We look at whether yellow teeth are a sign of poor health, and what you can do to improve the appearance of yellow teeth.

3在本文中，我们将深入探讨牙齿颜色背后的科学。我们看看牙齿发黄是否是健康不佳的标志，以及人们可以做些什么来改善牙齿发黄的状况。

Are teeth naturally yellow?

牙齿天然就是黄色的吗？

4那么，牙齿本来是黄色的吗？想了解更多信息，我们首先要深入了解牙齿的构成。它们由三个不同的层组成。牙釉质是人体内最坚硬的物质，形成了最外层；牙本质在中间；最内层是牙髓。很少有人意识到是牙本质（牙齿的中间层）赋予了牙齿颜色。对大多数人来说，牙本质是淡黄色，但红色调或琥珀色调也属正常。

4So, are teeth naturally yellow? To find out more, we first need to delve into the composition of our teeth.They are made up of three different layers.Enamel is the hardest substance in the human body and forms the outermost layer, dentin is in the middle and the innermost layer is pulp.Not many people realize that it is the dentin, the middle layer of a tooth, which gives it color.For most of us, the dentin is a pale yellow but shades of red or amber are normal too.吗？想了解更多信息，我们首先要深入了解牙齿的构成。它们由三个不同的层组成。牙釉质是人体内最坚硬的物质，形成了最外层；牙本质在中间；最内层是牙髓。很少有人意识到是牙本质（牙齿的中间层）赋予了牙齿颜色。对大多数人来说，牙本质是淡黄色，但红色调或琥珀色调也属正常。

5The color that we see is often more about the thickness of the enamel than the color of our teeth.

5我们看到的颜色通常更多反映了牙釉质的厚度，而不是牙齿的颜色。

6While there may be variation in the color of our teeth even from an early age, most people’s primary teeth appear whiter than their adult teeth.Dr.Sameet Hindocha explains that primary teeth appear whiter “because the enamel of babies’ teeth is thicker, which hides the yellow of the dentin underneath.”

6虽然我们的牙齿颜色可能从很小的时候就有差异，但大多数人的乳牙看起来比他们的恒牙更白。萨米特·欣多查医生解释说，乳牙看起来更白，是“因为婴儿牙齿的牙釉质更厚，掩盖了下面牙本质的黄色”。

Are yellow teeth a sign of poor oral health?

黄牙是口腔健康不良的标志吗？

7牙齿发黄是很自然的事情，不一定是口腔健康不良的迹象。即使拥有健康的生活方式，无法控制的因素也会影响我们牙齿的外观，例如基因和牙釉质厚度。随着年龄增长，牙齿通常会越来越黄，这是衰老过程的一部分。欣多查医生在接受美国趣味科学网采访时说：“随着年纪增加，我们的牙釉质会变薄或分解，这意味着牙齿内部的部分会更多地显示出来，使牙齿看起来更黄或奶黄。此外，茶和咖啡等一些食物和饮料的染色也会导致牙齿变黄。”黄牙不一定是口腔健康不良的标志，但有时候这也可能表明牙釉质已被侵蚀，此时牙齿可能很脆弱并容易缺坏。

7It is perfectly natural to have yellow teeth and this is not necessarily a sign of poor oral health.Even with a healthy lifestyle, factors outside of our control can affect the appearance of our teeth such as our genes and the thickness of our tooth enamel.Our teeth often appear more yellow over time as part of the aging process.Dr.Hindocha told Live Science: “As we get older, our enamel thins or breaks down which means that the inner part of the tooth shows through more, making the teeth appear more yellow or creamier.Additionally, staining from certain foods and drinks, including tea and coffee, can also contribute towards the yellowing of teeth.” Yellow teeth are not necessarily a sign of poor oral health, though in some cases it may signal that the enamel has eroded and that the teeth could be weak and prone to chipping.

8Dr.Hindocha added: “There are a number of other factors which may affect the color of our teeth.Silver fillings can discolor the teeth grey as they release ‘corrosion’ products over time.Teeth that have suffered from trauma or dental abscesses may also appear darker over time as the nerve may die away and require treatment.Some people may genetically have discoloration of their teeth and this is usually related to discoloration inside the tooth.” A study in theBritish Dental Journalshows that some metabolic disorders are associated with tooth discoloration as well as the use of medications like tetracycline.

8欣多查医生补充说：“还有许多其他因素可能会影响牙齿的颜色。银质填充物会使牙齿变灰，因为它们会随着时间的推移释放出‘腐蚀’产物。受过外伤或牙脓肿的牙齿也可能随着时间的推移显得更黑，因为牙齿神经可能坏死并需要治疗。有些人的牙齿可能会有遗传性变色，这通常与牙齿内部变色有关。”《英国牙科杂志》刊登的一篇论文表明，一些代谢紊乱或使用四环素等药物与牙齿变色有关。

9Our lifestyle choices can also influence the color of our teeth.Smoking can cause teeth to yellow rapidly.The tar and nicotine in tobacco are responsible for this staining effect.Coffee, red wine, chocolate, and fizzy drinks can all contribute to discoloration.

9我们选择的生活方式也会影响牙齿的颜色。吸烟会导致牙齿迅速变黄，是烟草中的焦油和尼古丁造成的这种染色效果。咖啡、红酒、巧克力和碳酸饮料都会导致牙齿变色。

What can you do about yellow teeth?

10While yellow teeth are not necessarily unhealthy, for many people the appearance of their teeth can affect their confidence.Luckily, there are changes we can make to improve how our teeth look.Maintaining good oral hygiene is an important preventative strategy.Experts recommend regular tooth brushing and flossing, plus mouthwash can be beneficial.

黄牙怎么办？

10虽然黄牙不一定意味着不健康，但对许多人来说，牙齿的外观会影响他们的自信。幸好，我们可以做出一些改变来改善牙齿外观。保持良好的口腔卫生是一项重要的预防策略。专家建议有规律地刷牙和使用牙线，另外，漱口水也有好处。

11Lifestyle changes can help improve the appearance of your teeth.Quitting smoking can make a huge difference, as can reducing consumption of food and drinks which stain the teeth such as coffee.

11改变生活方式有助于改善牙齿外观。戒烟有很大作用，减少摄入咖啡等会使牙齿染色的食物和饮料也有帮助。

12You should be aware that tooth whitening treatment does not change the color of fillings and crowns; these would need to be replaced if you wanted to change their appearance.Common side effects of tooth whitening are sensitivity and gum irritation.Dr.Safa Al-Naher warns against procedures carried out by non-dental professionals or without a prescription.She explained that:“They do not have the same accountability to a professional organization so there is a risk the product may not be safe and could cause damage.” ■

12要明白，牙齿美白治疗不会改变填充物和牙冠的颜色。如果想改变它们的外观，就要换掉这些。牙齿美白的常见副作用是牙敏感和牙龈刺激。莎法·纳赫尔医生提醒，不要由非牙科专业人员或在没有处方的情况下进行治疗。她解释说：“他们不像专业组织那样承担责任，因此产品可能存在风险，并可能造成牙齿损坏。” □