Toothbrush or Carrots: Medical Assistant Students Explore Bacteria in the Mouth

What do carrots have in common with brushing your teeth? Globe University-Madison East students in the medical assistant program set out to answer that question when they visited second graders at Cottage Grove Elementary School.

Second graders in Ms. Riley and Ms. Melde’s class learned about how oral bacteria can cause cavities by using dietary sugars and acids. They also learned how eating different foods can alter the amount or type of bacteria in the mouth. Medical assistant students worked with second graders to perform an experiment comparing the amount/type of bacteria in their mouths after eating different foods (gummy bears or carrots).

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Medical assistant student Kari Wooley swabs a student’s mouth after she had some gummy bears.

Prior to eating, the second graders brushed their teeth and the medical assistant students swabbed the inside of their mouths and spread the material onto bacterial culture plates that provide the required nutrients for bacterial growth. This served as the control, for comparison. Culture swabs were taken after eating gummy bears and again after eating carrots, with teeth brushing after eating the first food.

There were two groups: one group ate carrots first and then gummy bears; the other group ate gummy bears and then carrots. Following a five-day incubation period, the growing bacteria were photographed using an iPad®. The medical assistant students shared the photos with the second graders using their iPads.

The results showed an interesting trend; the oral bacteria that grew after eating gummy bears were clearly different in appearance from those that grew after eating carrots. There are many types of bacteria that are present in the mouth, but only a few are known to cause cavities. The bacterium most commonly associated with cavity formation is Streptococcus mutans. It is possible that the type present after eating carrots could be “good” bacteria that may inhibit the growth of more harmful types.

The second graders pointed out that both carrots and gummy bears contain sugar, but that these may be different sugars. Interestingly, eating carrots before eating gummy bears appeared to prevent the gummy bears from causing heavy bacterial growth. The group hypothesized that this effect was due to the fiber in the carrots, as crunchy fruits and vegetables are known to have a “toothbrush” action.

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Medical assistant students share photos of the bacteria with the students using their iPads.

“When the results are considered, this simple exercise was actually quite sophisticated,” said medical assistant instructor Michelle Cotroneo. “As with any good experiment, it answered questions and created more questions that can be answered by doing additional experiments. I was impressed by the consistency of our results and by the second graders’ knowledge about making healthy food choices, knowing that my own kids will eventually be in charge of what they eat.”

“It was so enlightening working with the kids. They were so excited to participate with us, which made it all the more fun,” said medical assistant student Lisa Luckasson. “Kids can say funny stuff, and they were so excited about asking questions. Sometimes in order to work with others you have to know what excites them!”