关于龋齿（蛀牙）

To understand what happens when your teeth decay, it's helpful to know what's in your mouth naturally. Here are a few of the elements:

Saliva — Your mouth and teeth are constantly bathed in saliva. Although we never give much thought to our spit, this simple fluid is remarkable for what it does to help protect our oral health. Saliva keeps teeth and other oral tissues moist and lubricated, washes away some of the food particles left behind after we eat, keeps acid levels in the mouth low, and protects against some viruses and bacteria.
Plaque — Plaque appears as a soft, gooey substance that sticks to the teeth a bit like jam sticks to a spoon. It is, in fact, colonies of bacteria, protozoa, mycoplasmas, yeasts and viruses clumping together in a gel-like organic material. Also in the mix are bacteria byproducts, white blood cells, food debris and body tissue. Plaque grows when bacteria attach to the tooth and begin multiplying. Plaque starts forming immediately after a tooth is cleaned; it takes about an hour for plaque to build up to measurable levels. As time goes on, different types of microorganisms appear, and the plaque thickens.
Calculus — If left alone long enough, plaque begins to mineralize and harden into calculus or tartar because the plaque absorbs calcium, phosphorus and other minerals from saliva. These minerals form crystals and harden the plaque structure. New plaque forms on top of existing calculus, and this new layer can also become calcified.
Bacteria — We have many different strains of bacteria in our mouths. Some bacteria are good; they help control destructive bacteria. When it comes to decay, Streptococcus mutans is the bacterial strain that does the most damage. It attaches easily to teeth and produces acid.

How Your Teeth Decay

You need food, particularly sweet and sticky food, for the bacteria in your mouth to produce acids that will attack the tooth enamel (outer surface of the tooth). Sugars, especially sucrose, react with bacteria to produce acid. The acid from the bacteria can decay your teeth.

It's not just candy and ice cream we're talking about. All carbohydrate foods, as they are digested, eventually break down into simple sugars, such as glucose and fructose. Some of this digestion begins in the mouth. Foods that break down into simple sugars in the mouth are called fermentable carbohydrates. These include the obvious sugary foods, such as cookies, cakes, soft drinks and candy, but also pretzels, crackers, bananas, potato chips and breakfast cereals. The sugars in these foods combine with the bacteria normally in the mouth to form acids. These acids cause the mineral crystals inside the teeth to begin to dissolve.

The dental caries lesion forms when these acids start to dissolve a tooth's outer protective layer, the enamel. A cavity forms when the tooth decay breaks through the enamel to the underlying layers of the tooth. You can reverse a caries lesion (before it becomes a cavity) by using a variety of fluoride products. These include fluoridated water, fluoride rinses for use at home, and, of course, any commonly used fluoridated toothpaste.

Every time you eat, the bacteria in your mouth produce acid. Therefore, the more times you eat the more times your teeth are exposed to an acid attack.

Types and Stages of Decay

Dental decay, also known as dental caries, begins first inside the tooth. A white spot appears on the enamel where the tooth has started to weaken inside. At this stage, the tooth can repair the weakened area with the help of fluoride and minerals in saliva. But if the decay continues and breaks through the surface of the enamel, the damage is permanent. The decay must be cleaned out and the cavity filled by a dentist. Left untreated, the decay will worsen and destroy a tooth all the way through the outer enamel layer, through the inside dentin layer and down to the pulp or nerve of the tooth.

In young children, teeth that have recently emerged have weak enamel and are highly susceptible to acid decay. A type of decay called baby bottle tooth decay or early childhood caries destroys enamel quickly and is common in children. This type of decay can eat through enamel and leave a large cavity in a matter of months.

Older adults sometimes have chronic caries: cavities that don't seem to get any worse or do so at a very slow rate. Teeth with chronic caries will tend to be darker in color because the edges of the cavities become stained from normal eating and drinking.

Root caries (decay in the roots of the teeth) is more common in older adults. Older adults are more likely to have gums that have receded from years of hard brushing or periodontal disease. They also are more likely to have dry mouth (xerostomia), which increases the risk of decay. Dry mouth is caused by many common medicines. Be sure to ask the doctor or pharmacist if any of your medicines cause dry mouth.

Decay can form beneath fillings or other restorations, such as crowns. Sometimes, bacteria and food particles can slip into a tooth if a filling hasn't been placed properly or if the filling cracks or pulls away from the tooth, leaving a gap.

Preventing Cavities

Do you or your family members get cavities frequently? Dental research has identified factors that increase your risk of getting decay. Next time you visit the dental office, ask about your risk factors and discuss the best ways to reduce your risks and limit dental decay.

To prevent your teeth from decaying, you can do two things — strengthen your teeth's defenses with fluoride and sealants, and reduce the number of bacteria in your mouth.

Fluoride strengthens teeth by penetrating the tooth structure and replacing lost minerals to repair acid damage. Everyone should brush with a fluoride toothpaste every day. Dental offices sometimes recommend additional toothpastes, gels and mouthrinses for both children and adults.

Sealants are protective coatings placed over the tops of chewing teeth — molars and premolars. They block bacteria and acids from sticking in the tiny grooves on the chewing surfaces of these teeth. Children should get sealants soon after their teeth erupt into the mouth.

Although you can never get rid of all the bacteria in your mouth, you can control bacteria by brushing regularly and flossing daily, seeing your dentist and dental hygienist regularly for a thorough cleaning and check-up, and reducing the number of times each day that you consume fermentable carbohydrates.

Some prescription mouthwashes (those that contain chlorhexidine) can help prevent decay by reducing the number of bacteria in the mouth. Chewing sugarless gums, especially those with xylitol, can help reduce decay and increase the flow of saliva.

为了理解当你的牙齿龋坏时都发生了什么，了解你口腔的自然状况是有益的。以下是几个基本组成要素

唾液— 你的口腔和牙齿都不断被唾液洗刷。尽管我们从未对唾液有太多关注，这种液体对保持你的口腔健康是非常重要的。唾液保持牙齿及其他口腔组织湿润和润滑，清洗我们吃饭后遗留的食物残渣，保持口底的酸碱度，抵抗一些病毒和细菌的侵扰
菌斑 — 菌斑表现为一种软的，粘性物质贴在牙齿上，就想粘在汤勺上的果酱。事实上，它是细菌，原虫，支原体，酵母和病毒的聚集地，形成凝胶样的有机物质。其中也包含有细菌分解的产物，血细胞，食物残渣和自体组织。当细菌粘附到牙齿上并增值，菌斑就开始增长并开始。菌斑在牙齿被清洁之后就开始形成，它在1小时内就能达到可检测到的水平。随着时间延长，不同类型的微生物出现菌斑也开始增厚。
牙结石— 如果菌斑呆的时间足够长，它就开始矿化变硬形成牙石或牙垢，因为菌斑从唾液中吸收了钙，磷和其他 矿物质。这些矿物质形成了菌斑的结晶变硬的结构。现有牙齿表明又形成新的菌斑，而新的菌斑层也逐渐矿化。
细菌— 我们口腔里是有不同类型的细菌的。一些事有益菌；它们帮助控制有害菌。当发生龋齿，链球菌在破坏中起到主要作用。它很容易粘附牙齿并产生酸。

你的牙齿是如何龋坏的

你需要食物，特别是甜食和粘性食物，你口腔中的细菌就会利用它产酸并损害牙釉质（牙齿表面光亮的那一层）。糖，尤其是蔗糖，会被细菌利用产酸。而产生的酸可以腐蚀你的牙齿。

我们说的不仅仅是糖果或者冰激凌。一切碳水化合物的食物，因为他们经消化后最终变为单糖，比如葡萄糖和果糖。一些消化就开始于口腔。食物在口腔内分解的糖称之为可发酵的碳水化合物。其中包括明显的含糖的食物，如饼干，蛋糕，软饮料和糖果，也包括椒盐脆饼，饼干，香蕉，土豆片和早餐食品。在这些食品中的糖通常结合细菌在口腔内产酸。这些酸导致牙齿内的矿物晶体开始溶解。

当这些酸溶解牙齿外层的保护层-釉质层，龋坏就开始了。当蛀坏到突破了牙釉质层，龋齿就形成。使用各种不同的氟产品，你是可以扭转龋齿病变的（在它发展为龋齿之前）。其中包括家用的含氟饮用水，氟漱剂，当然，最常用的是含氟牙膏。

每当你吃饭的时候，细菌就开始产酸。所以你吃的时间越长，你的牙齿暴露于酸的攻击的时间就越长。

龋坏的类型和阶段

牙齿腐坏，就是龋齿，首先会减弱牙齿内的保护。牙釉上有个白色斑点，对牙齿内部的保护就减弱。这个时期，在氟化物和唾液中矿物质的帮助下，牙齿可以修复薄弱部位的。但是如果龋坏继续进行穿过表面的牙釉质，将会形成永久性损害。必须由牙科医生把龋坏清理干净并充填。如果不治疗，龋坏会继续发展，穿过牙齿外面的牙釉质层，穿过牙本质层进入髓腔或者牙齿的神经。

最近表明，小孩子的牙釉质极易受酸侵蚀。 A型龋齿称为奶瓶龋或幼儿龋齿，破坏牙釉质非常迅速，常见于儿童。这种类型的龋坏可以通过腐蚀牙釉质在几个月后形成大的龋洞。

老年人有时有慢性龋坏：龋齿似乎没有得到任何恶化或进展的很慢。牙齿慢性龋将趋于较深的颜色，因为边缘龋洞被正常吃的食物所染色。

根面龋（牙齿根部的龋坏）较常见于中老年人。老年人的牙龈更可能有从多年的辛勤刷牙或牙周疾病而萎缩。他们也更可能有口干（口干燥症），增加了龋坏风险。口干可有许多常用药物引起。如果你有药物引起的口干一定要询问医生或药剂师。

龋齿也可以在有充填物或者修复体的牙齿上发生，比如牙冠。如果充填体位置不良或者充填体裂开，脱落，留下缝隙，细菌和食物颗粒就可以进入牙齿。

龋病预防

你和你的家人经常患有龋齿吗？牙科研究发现一些增加龋齿风险的一些因素。等你下次拜访牙科诊所的时候，询问医生你的危险因素并讨论最好的办法去减少危险因素限制龋坏的发生。

为了预防龋坏的发生，你可以做两件事情--用氟化物和封闭剂增强牙齿保护，减少口腔内细菌。

氟化物可以增强牙齿保护，是通过进入牙齿结构，重新矿化修复酸所带来的破坏。每个人需要每天用含氟牙膏。牙科诊所有时推荐额外的牙膏，口香糖和漱口水，小孩大人用的都有。

封闭剂在是牙齿咀嚼面上覆盖一层保护材料--在磨牙或者前磨牙。它们可以阻止细菌或酸的侵入牙齿表面的窝沟。小孩子在牙齿萌出后应该做牙沟封闭。

尽管你不可能完全清楚口腔内的细菌，但你可以通过定期刷牙和每日用牙线，定期去看牙医或者牙科保健员洁牙和检查，减少你吃可发酵的碳水化合物食物的次数，来控制细菌数量，

一些处方漱口水（含有氯已定）可以减少口腔细菌数目而预防龋坏。咀嚼无糖口香糖，尤其是含木糖醇的，可以帮你减少区划和增加唾液流动。