The oral microbiome of children, and its relation to dental caries

The oral microbiome is a popular area of exploration because bacteria are a prominent part of dental health, and because it is one of the most heavily colonized and easily accessible niches in the body. Many studies have been discussed on this blog concerning adult oral microbiomes, and its relations to bodily issues such as cystic fibrosis and periodontitis. It is also very useful to investigate children and the ways that their bacterial communities first inhabit and develop. A study done in Sweden at the Umeå University, and published by Plos One, takes a look at the maturation of the oral microbiome from infants at 3 months old to children at 3 years old.

The Swedish researchers performed a longitudinal study that followed children from 3 months to 3 years of age, looking for microbial characteristics of children with dental caries (i.e. cavities) compared to those without. There were 207 original participating 3 month olds that were consented by their parents to be in the study. The parents provided information on mode of feeding, mode of delivery, use of antibiotics or probiotics, health issues like allergies, and presence of teeth. At 3 months and later at 3 years samples were taken from the buccal mucosa, tongue, and alveolar ridges. Teeth were also scraped for plaque and saliva was collected. Of the original 207 participants, 155 returned for sampling at 3 years of age, and 13 of those children had dental caries.

After sequencing the bacterial DNA samples, it was found that Escherichia coli, Staphylococcus epidermidis, and various Pseudomonas species were significantly more prevalent in 3 month olds. However, there were 23 genera that were more significantly prevalent at 3 years of age than at 3 months.

By comparing the children with and without caries, the scientists were able to make several conclusions.  The researchers identified seven taxa that appear to be associated with healthy teeth.  On the other hand, Streptococcus mutans seemed to be more prevalent in the children with caries, than in those without caries. Additionally, the colonization of this species was most prevalent in girls. This is possibly because girls develop faster, so earlier tooth eruption allows for a longer time for the colonization of these bacteria.

The results of this study show us that during the first three years of life, species richness and diversity seems to increase significantly in the mouth. While there is an increase in the type of the bacteria, there are also some taxa that are lost with age. The researchers also concluded that the oral microbial composition of the mouth at 3 months does not appear related to the development of dental caries. With this information, it might be smart to perform a related study that collects oral microbiome samples in children within the time frame of 3 months to 3 years, because it could show a clearer picture of the changes that take place in bacterial composition.

Walk, chew gum, and fight cavities all at the same time

Chewing gum has been suggested to have many cognitive benefits such as increasing focus and alertness, improving memory, and controlling, besides its obvious benefit of making breath smell minty fresh.  What about gum's effect on our microbiome though?  Could gum help prevent cavities in the same way as tooth brushing or flossing?  In order to find out, researchers from the Netherlands and Wrigley, the gum company, recently published the results of a study in PLoS One that set out to answer the question: how much oral bacteria is trapped and removed by chewing gum?

In order to test the hypothesis, volunteers chewed gum for various times for up to 10 minutes. The researchers then used different quantitative and qualitative analyses, such as culturing and genomic analysis, to measure the amounts of bacteria collected in the gum.  The researchers found that the chewing gum does indeed trap around 100 million bacteria, which is about the same as brushing your teeth with a new, clean toothbrush without using toothpaste. They also state that chewing gum could prevent biofilm formation, much like tooth brushing.  Finally, they concluded that the longer gum is chewed, the fewer bacteria it removes from the mouth.

This study in quantifying bacterial removal by gum was preparing the researchers for their next project, which is to intelligently design gum to prevent cavities.  As we know there are healthy and harmful bacteria in the oral cavity, but the study did not investigate which types of bacteria were removed.  If gum could be designed that preferentially adsorbs and removes acid-forming bacteria like Streptococcus mutans then it could be highly effective in eliminating cavities.  We look forward to reading more about this project, and in the meantime, if you’re going to chew gum, try and make sure it’s sugar free.

Could ice cream prevent cavities?

We know that the oral microbiome hosts a wide variety of bacteria, some good, and some that cause cavities.  Those that cause cavities do so by producing acid as they break down the food in our mouths.  Researchers in India are trying to discover if probiotics could help alter the oral microbiome so there is a decrease in the bacteria that commonly cause cavities.  In their study they investigated a type of ice cream sold in India that has the probiotics Bifidobacterium bifidum and Lactobacillus acidophilus mixed in with the ice cream.  The researchers were interested in the effects the probiotic ice cream on the levels of bacteria and fungi in saliva, namely Streptococcus mutans, Lactobacillus acidophilus, and Candida albicans, because these three bacteria are the main causes of tooth decay.  The results were recently published in the Journal of Dental and Medical Sciences.

In the study, the researchers gave 20 participants one dish of ice cream each day for 10 days that either contained the probiotics or did not.  The researchers examined the bacteria in the participants’ saliva both before and after the ice cream intervention.  The results showed that consumption of probiotic ice cream caused a significant reduction of both S. mutans and C. albicans, and an increase in the number of L. acidophilus when compared to controls.  The increase in L. acidophilus is not surprising because the ice cream contained L. acidophilus. The researchers highlighted that in other studies of people eating Lactobacillus acidophilus, it did not persist in the individuals’ mouths.  Overall, two of the cavity causing bacteria decreased in abundance and one, which was in the probiotic ice cream, increased in abundance.

We must admit that the rigor of this study was highly lacking, so we don’t want anyone to take these results too seriously. While more research needs to be done to determine if probiotic ice cream can actually help prevent cavities and tooth decay, any study that recommends eating it is fine by me.  It’s obviously important to brush your teeth every day, but it’s definitely more fun to eat ice cream than to floss!