"We decided to focus on children because we hypothesized two things -- that the oral microbiome rapidly changes with age, and also that child twin pairs are likely to have a shared environment," Nelson explained. "This allowed us to better control the influence of shared and unique environments."

Their results showed that identical twins had oral microbiomes that were more similar to each other than those of fraternal twins, indicating that there is genetic contribution to which kinds of bacteria are likely to be present in the mouth.

However, the taxa that were linked most closely to heritability were not the ones that play a role in cavity formation, they noted.

In addition, they found that the heritable strains of bacteria decrease in abundance as people get older, whereas the ones linked to the environment increase.

"An important additional finding was the link between certain bacterial species and sugar consumption," the team said.

"Bacteria that were associated with fewer cavities were in lower abundance in twins who had a lot of added sugar in their food and drinks. In contrast, bacteria that are more common in children who consume a lot of sugar were associated with having more cavities."

The team planned to continue studying the twins over repeat visits to examine changing patterns in the oral microbiome. They are also looking at functional differences in the oral microbiomes of identical and fraternal twin pairs that have various states of oral health.