In 2011-2012, dental cavities, or caries, affected 91% of adults aged 20-64 years in the US, exacerbated by consumption of sugary foods and drink, lack of oral hygiene and not paying regular visits to the dentist.
For the mouth to stay healthy, pH levels must be neutral. Too much acid can cause dental cavities or other disorders.
Acid in the mouth causes bacteria on the teeth to create more acid, and acid dissolves the teeth.
Researchers at the University of Florida (UF) College of Dentistry, led by Robert Burne, PhD, and Marcelle Nascimento, PhD, wanted to know what causes high pH.
Their search revealed a new strain of bacteria that could keep bad bacteria under control, and pave the way to using probiotics to prevent cavities.
Keeping a balanced pH in the mouth
Previous research by the same authors has found that two main compounds are broken down into ammonia, and this helps to neutralize acid in the mouth.
The two compounds are urea, which everyone secretes in the mouth, and arginine, an amino acid. The researchers already knew that people who had few or no cavities were better at breaking down arginine than those with cavities.
Fast facts about cavities
In 2011-2012, 17.5% of 5-19-year-olds had dental caries
Among those aged 20-44 years, the figure was 27.4%
83% of those aged 2-17 years visited the dentist in the previous year.
Learn more about oral health care
They knew that bacteria were responsible for breaking down these compounds, but did not know which bacteria do this best, or how this activity prevents cavities.
Part of the answer is a previously unidentified strain of Streptococcus, currently called A12.
Samples of dental plaque, the bacteria that grow on the surface of teeth and can contribute to the formation of cavities, were collected for the study.
Over 2,000 bacteria were then screened to find the right one. The team characterized 54 bacteria that metabolized arginine. Of these, A12 had all the properties needed to prevent cavities probiotically.
The researchers then sequenced the entire genome of A12.
They hope to use the findings to develop a screening tool for people with a higher risk of developing cavities, alongside other factors, such as diet and oral hygiene habits.
Nascimento says that if they can confirm that people with a higher level of A12 develop fewer cavities, A12 could be used to measure for cavity risk.
‘Good’ bacteria to fight the bad
Burne explains that, just as we might use a probiotic approach to the gut to promote health, a similar strategy could be effective for the mouth.
“You would implant this probiotic in a healthy child or adult who might be at risk for developing cavities. However many times you have to do that, once in a lifetime or once a week, the idea is that you could prevent a decline in oral health by populating the patient with natural beneficial organisms.”
The fact that A12 helps to neutralize acid by metabolizing arginine was not the only discovery. The authors also found that A12 often kills Streptococcus mutans, an especially harmful kind ofl bacteria.
Even when A12 did not kill S. mutans, it hindered it from causing disease by disrupting the processes.
Burne points out that growing A12 and S. mutans together reduced the ability of the bacterium to develop properly or to make biofilms, also known as dental plaque.
S. mutans metabolizes sugar into lactic acid, and this contributes to the acidic conditions that form cavities.
Meanwhile, the researchers hope to carry out a larger study to find more instances of A12, and to test how prevalent bacteria with similar properties are in the human mouth.
While the development of an effective oral probiotic is still a long way off, A12 looks a promising candidate.
Medical News Today reported last month that people who sleep with their mouth open may have a higher risk of tooth decay.
Written by Yvette Brazier