The real reasons why cavities form

Casey Ewing* was doing everything right with her daughter’s teeth: She brushed Melissa’s* pearly whites twice a day, took her to the dentist for the first time just after she turned one and kept up with the recommended schedule for professional cleanings. So, imagine Ewing’s disbelief when, after Melissa’s first set of X-rays at around age four, she learned her daughter had eight cavities. “I was shocked and embarrassed,” Ewing says. “I kept trying to figure out if I’d neglected to do something, and I couldn’t believe that after all my attention to her teeth, she could have such a significant problem.”

But Melissa isn’t alone. According to the Canadian Institute for Health Information, between 2010 and 2012 (the most recent data available), almost 30,000 Canadian children under the age of five underwent day surgery to treat tooth decay. (It’s rare for kids this young to be able to sit for a filling or an extraction, so they often have to undergo sedation and sometimes general anaesthesia.) Katherine Ing, a paediatric dentist, isn’t surprised the stat is that high. “I’ve steadily seen cavities in preschoolers throughout my career,” she says. “Sometimes the number of kids with cavities fluctuates, depending on things like the level of fluoridation in a community’s water, socio-economic status and trends in diet, but it’s pretty consistent.”

Ing stresses that cavity development is a complex issue, though, and one of the primary reasons is not what many expect. “Above everything else, you have to have the cavity-causing bacteria in your mouth,” says Ing. “Kids are born without cavity-causing bacteria and acquire this infection from those closest to them.” These bacteria, called streptococcus mutans, or strep mutans, interact with sugar on the teeth and leave people vulnerable to cavities. Most, if not all, people end up having strep mutans in varying quantities—the higher the level of bacteria, the more susceptible someone is to tooth decay. But don’t expect your dentist to run tests on whether or not you have it—the infection is just too common. “It’s almost impossible to halt the spread of strep mutans in families,” says Ing, “but there are ways to limit exposure. Try to avoid sharing utensils or food, and of course, everyone should have their own toothbrushes.”

Healthy oral habits are also key to preventing the bacteria from totally taking over. Kids should brush twice and floss once a day to remove the plaque formed by bacteria, and Ing suggests mom or dad check the brushing and flossing work until children are at least seven. “It might seem like a long time, but kids aren’t going to be nearly as careful as their parents.” As for toddlers or preschoolers who put up a fight? “It has to be non-negotiable,” Ing says. “I have parents in my practice who have to hold their kids down to brush and floss. It’s hard, but the alternative is potentially surgery to repair cavities.”

Of course, brushing isn’t the only factor. Dentist Alan Kwong Hing says what kids eat also plays a role. Sugar is the biggest factor—the bacteria feed on all forms of sugar and turn them into acid, which eats away at tooth enamel. But there’s more to it than just limiting gummy bears. “Chewy candy is obviously a no-go, but there are hidden sugars in so many things,” says Kwong Hing, adding that rinsing with water after a snack or meal is a good idea. “Parents need to be wary of things like dried fruit, fruit juices and even milk.” Young kids who go to bed with bottles, or who nurse to sleep, are especially at risk. “Any kind of milk right before or at bedtime, after brushing, negates all the good brushing does,” adds Ing. “The sugar turns to acid and sits on the teeth all night.”

Of course, there are also some genetic factors in the mix. “Children might inherit deeper grooves in teeth, a smaller jaw with crowded teeth or thicker saliva, which all lead to acid staying on the teeth longer,” says Ing. But enamel strength isn’t hereditary. “There’s no such thing as soft teeth.” Genetic risk factors can be mitigated with habits like careful flossing between teeth that are touching (those tight-fitting teeth turned out to be the cause of Melissa’s first cavities), using an electric toothbrush or enforcing proper techniques with a manual one, and keeping up with regular dentist’s visits to help monitor problem areas.

Adopting these habits has been the best approach for Melissa, who is now 16. “She has known since she was in kindergarten that she has to brush and floss diligently, because her teeth are still really close together, and that she can’t miss a dentist’s appointment,” says Ewing. “And I’ve now become a voice of reason for parents going through dental issues with their kids—there are so many factors at play, so you can’t feel bad. All you can do is your best.”

* names have been changed

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