How Cavities Work: Understanding the Process of Dental Decay

Cavities: it’s a word we all fear hearing at the dentist. But despite the fact that you’ve probably known about the existence of cavities since you were a child, many people are confused about what exactly cavities are and how they form. How do they happen? Are they always due to not brushing well enough? Can they be reversed? By understanding exactly how cavities are created, you can gain greater insight into your own oral health and how to prevent decay.


The first step to understanding cavities is to understand the basic elements involved in protecting against or contributing to tooth decay:

  • Bacteria: The mouth is home to dozens – or, in extreme cases, hundreds – of bacterial strains. The majority of these strains are harmless or even beneficial, as they help us digest foods and maintain a healthy oral environment. However, some bacterial strains can wreak havoc on our dental health.
  • Saliva: The healthy human mouth produces saliva in varying amounts throughout the day, which serves to lubricate oral tissues, regulate acidity, remove food particles, and offer protection against bacteria and viruses.
  • Plaque: Plaque is a sticky, colorless film made of bacteria, yeast, mycoplasmas, and viruses that continuously forms on the surface of the teeth throughout the day. Although plaque is natural and unavoidable, it can also cause serious damage to tooth structures; when left on the teeth, it may become acidic and cause demineralization or harden into tartar, which can no longer be removed via regular brushing or flossing.
  • Tartar: Once plaque has hardened into tartar, also known as calculus, it can no longer be removed via regular brushing and flossing. Instead, it forms a rough and uneven surface that creates a perfect environment for plaque to accumulate and breed more tartar.


Many people believe that cavities are caused by sugar; this is, after all, what most of us have been told since we were kids as we were warned against the dangers of candy and sugary sodas. However sugar itself does not directly cause cavities. Instead, the decay process begins when specific bacterial strains in plaque are supplied with sugar, causing the bacteria to produce acids that dissolve the outer layer of the tooth surface, called enamel. At this stage, decay is referred to as caries. Once the enamel is deteriorated and the decay reaches the dentin, or the underlying structure of the tooth, a cavity forms.

The primary bacterial strain responsible for tooth decay is called Streptococcus mutans, which thrives on not only sugars, but also starches, which are fermented into acids by oral bacteria. This means that it’s not just sugar-rich sweets that contribute to cavities, but also healthy foods like cereals, bananas, corn, breads, green peas, and potatoes. According to some research, these cooked starches present a particularly high danger to our oral health; as Dr. Harald Linke of the New York University Dentist has found, “cooked starches cling longer to the teeth than many sugar foods, like chocolate bars, thus leading to a longer period of acid production."


Aside from differences in oral hygiene routines, there is great fluctuation in people’s susceptibility to dental decay. Genetics, diet, and medications can all play a significant role in both the strength of our enamel, our propensity of plaque accumulation, and the likelihood of acid formation. Certain life stages may also increase our risk for decay; young children, for example, may be prone to cavities due to the weakness of the enamel in newly formed teeth while seniors are more likely to have inadequate saliva production, leaving them without a natural defense against acid formation. In short, there are multiple, complex factors contributing to cavities, which is why people with excellent oral hygiene can be plagued by re-occurring cavities while people with less than ideal habits can go a lifetime without any cavities at all.


Our teeth are living organisms that are constantly in a state of flux as they undergo demineralization and remineralization processes throughout the day. Through proper oral hygiene using fluoride products, healthy saliva production, and certain in-office dental procedures, it may be possible to remineralize caries that have not yet become cavities, effectively preventing a future cavity. However, only very small caries have the potential to be remineralized and once a cavity has formed, no amount of intervention will reverse the day. 


While virtually all people will have cavities at some point in their lives, there are important steps you can take to minimize your risk of tooth decay:

  • Brush at least twice every day and floss at least once. Make sure to pay special attention to the sides of your teeth and your back teeth, which is where cavities are most likely to form. Ideally, you should be brushing after every time you eat, particularly if you are eating sugary or starchy foods.
  • Use a fluoride rinse twice daily after brushing for about 90 seconds each time. To prevent drying of sensitive oral tissues, select a fluoride-containing mouthwash without alcohol..
  • Chew sugar-free gum with xylitol (birch sugar), such as Spry, which is proven to prevent caries from developing.
  • If you suffer from dry mouth due to medications or any other factors, stimulating healthy saliva production is critical to protecting your oral health. There are many high quality products on the market to stimulate saliva flow, including the Biotene product line and even artificial saliva available in drugstores.
  • Eat 3 meals daily rather than grazing throughout the day to give your mouth a chance to restore a healthy balance.

If you do suspect you have a cavity, it is important that you seek care as soon as possible to prevent further decay and preserve as much of your tooth structure as possible. By working with a dentist who offers the latest in laser dentistry technology rather than relying on traditional drills, you can ensure that your decay removal and filling preparation is as fast, comfortable, and stress-free as possible.


If you would like to learn more about how to prevent cavities or have any concerns about your oral health, we invite you to contact us any time at Dr. Kvarnstrom's Fountain Valley dental office. We are always happy to answer any questions you may have and invite you to set up an appointment to meet our dedicated and compassionate team.