What causes cavities and why do my kids keep getting them?

Dr. Sara Toema, D.D.S.Dr. Sara Toema, D.D.S. from our South Philadelphia office addresses one of the most common questions our doctors receive.

Many factors can cause an increase in the prevalence of dental cavities, or “caries,” the scientific term for dental decay. As a matter of fact, caries is recognized by the Centers of Disease Control and Prevention as the most common chronic childhood disease—more common than asthma!

The good news is that caries is preventable and can be arrested or even reversed if caught at an early stage. You may be saying, “My kids don`t eat candy, how come they have that many cavities?” Sweet treats like candy are one of the biggest causes of cavities, but they are not the only cavity-causing criminals out there!

To better understand the factors that can cause cavities, let’s take a look at how they are formed.

Cavities and Bacteria

The journey begins when we are born. Many different types of bacteria colonize the human body and become a normal part of it—what we call “normal flora.” Those bacteria live in harmony with each other and with our bodies in a symbiotic relationship—that is, until something goes wrong. When there is a disturbance in the normal bacterial balance, conditions change, allowing a disease process to occur. This is particularly true for dental caries.

One particular type of bacteria—Streptococcus Mutans (S.Mutans)—is believed to be the culprit of dental caries initiation. S.Mutans is present in our mouths and is relatively harmless until there is a disturbance in the ecology. When this happens, they rapidly increase in number, and this growing colony has an incredible ability to stick to outer tooth surfaces, forming plaque.

Plaque is a sticky film rich with bacteria and other salivary components. S.Mutans and other types of bacteria love plaque because it’s sticky and provides a perfect environment to multiply. These sturdy, energetic bacteria begin to break down sugar—or to be more precise, any fermentable carbohydrates—and convert it into acid and the energy the bacteria need to live and reproduce.

The acid that bacteria produce dissolves the calcium and other minerals in the tooth enamel, or the outer layer of the tooth, in a process called “Decalcification.” Once the calcium in the enamel is dissolved, the tooth enamel becomes weaker, and if the situation is allowed to progress, the affected spot will eventually become a cavity. So, what went wrong? What caused these bacteria to multiply?

Cavities: A Multifactorial Process

In short, many things could have gone wrong. This is why dental caries is known to be a multifactorial process, where a number of factors work in concert to produce the results. Something could have gone wrong with the tooth making it more prone to cavities, or something can be off balance with the bacteria or the oral environment. All that caries need to form are the right combination of factors and time. So, let`s elaborate a little more on some of the most important contributing factors.

  • Tooth Structure - Enamel Quality and Quantity - Some children are born with weaker enamel due to a thinner than usual or less mineral component of the outer layer of their tooth, leaving it more susceptible to decay. This could be caused by issues or illness during pre-birth or infancy, or genetic predisposition.
  • Tooth Anatomy - Grooves in Teeth - Some teeth, especially molars, are very groovy. Food can easily get stuck, plaque builds up there, and bacteria smartly reside deep in those grooves, making it the most common site of caries. As a matter of fact, research from the American Academy of Pediatric Dentists (AAPD) shows that 90% of caries in school-aged children are affecting the grooved surface of the tooth.
  • Bacterial Transmission - As we’ve discussed, bacterial imbalance is a leading cause of caries in children’s teeth.  Studies show that the earlier your child is exposed to large colonies of S.Mutans, the more they are likely to develop caries.  Bacteria could be acquired through  ‘vertical’ sources such as moving from care giver to child, or from ‘horizontal’ sources such as passing between children (from sharing utensils, cups and pacifiers, etc.)
  • Saliva Quantity and Quality - Saliva is a perfect bathing tool for the teeth. Not only because it washes debris off of dental surfaces, but also because it is supersaturated with calcium and other minerals that help build back demineralized teeth. However, if the saliva is too thick or there isn’t enough of it, then it won`t be able to do its job effectively. Some medical conditions, such as Diabetes and Ectodermal Dysplasia, cause the saliva to be ropy or scarce. The same can be true for some medications such as asthma inhalers.You may be saying, “wait, I’ve noticed that how much saliva I have changes throughout the day.” You’re right! Naturally, saliva becomes more fluid and increases when you are hungry or eating, and decreases and becomes thicker while we are asleep. That is one of the reasons why dental professionals discourage bed time feedings, and strongly encourage regular brushing and flossing before going to bed.
  • Mouth Muscles and Tongue - Together with the saliva, the muscles in your mouth and tongue act as your mouth’s washing machine. The tongue movement and the lips and cheeks massage during chewing, helping clear the mouth from food and sweep the teeth surfaces clean. Some children have tongue-tie leading to its limited range of movement. Other children have muscular or neurodevelopmental conditions that won`t allow all those oral muscles to function as desired such as in Cerebral Palsy. In these cases, additional steps are taken to address any shortfalls where the body isn’t able to perform these functions as effectively.
  • Teeth Crowding - When a person’s teeth are crowded or overlapping, they are naturally harder to clean and more likely to trap food in tough-to-reach spaces. This also creates perfect hiding spots and breeding grounds for bacterial colonies to flourish and cause caries.
  • Sugar Attack - Watch Their Diet - Bacteria uses not only sugars, but basically any fermentable carbohydrates and breaks it down into acids that can damage tooth surfaces. This includes juices, chocolate milk, chips, crackers, cereals, granola bars, raisins and, of course, candy. We could, no doubt, keep adding to the long list of S.Mutan`s favorite foods and drinks if we wanted to, but the key item to focus on here is really the length and frequency of exposure your teeth have to these foods.The stickier the food is, the longer it adheres to the teeth, and the longer the bacteria have to do their business. Similarly, the more frequently we expose bacteria to these foods and drinks, the more active they will remain. That’s why you have to be careful with things like sippy cups, which tend to release drinks very slowly in the mouth letting the bacteria work diligently, or bottle/breast feeding at night time or at random when the child desires it, as these factors are commonly associated with early childhood caries. 
  • Medications - Medications can be contributing factors to the appearance of childhood caries. Some medications decrease the salivary flow, such as prolonged use of asthma inhalers, and we know that reduction in the cleaning power of saliva can result in dental caries. Also, many children`s medications such as cough or allergy medicines are loaded with sugar to give them an improved flavor. When these medications are taken multiple times throughout the day and at night time, they serve as an ample source of sugar to feed bacteria.Another source of troublesome sugars are nutritional drinks, often used as a dietary supplement to help balance nutritional intake and promote needed weight gain. Gummy vitamins (maybe the biggest offenders in this list)  are both very sticky and loaded with sugars to improve the taste, so from a dentist’s perspective, it is like eating candy every day and should be treated as such.
  • Dental plaque - As we have learned, dental plaque is a harbor for bacteria. As we brush and floss our teeth we disturb that biofilm and decrease the number of bacteria adhering to the teeth surface—ultimately creating an inhospitable environment for bacterial colonies and reducing the damage their byproducts can inflict on tooth surfaces.

Now that you know why caries form, stay tuned for the next article from Dr. Sara as she discusses the best ways to prevent them!

Read Dr. Sara's Bio

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