An Army of Bacteria

What would you think if you heard there was an ‘army’ of microbes living in your mouth waiting to fight back at your best efforts to keep your teeth clean and cavity-free? Sounds a little out there, right?

Well, the idea is not so far-fetched, according to researchers at the University of Pennsylvania School of Dental Medicine and the Georgia Institute of Technology.

Teams from these schools imaged the bacteria that cause tooth decay in 3D to see how they behave in their natural environment: dental plaque.

‘Dental plaque is the sticky biofilm that covers the teeth in between brushings,’ said Dr. Richard Armstrong, a Waco, Texas, dentist.

The results of the study were published in the journal Proceedings of the National Academy of Sciences and revealed that the bacteria Streptococcus mutans, a primary contributor to tooth decay, exist in a protective, multilayered community of other bacteria and large molecules that form a unique organization in the area, causing decay.

Using teeth extracted from children with severe tooth decay, the researchers hoped to answer questions about how the bacteria were organized, and if the way they hold themselves could explain how they cause tooth decay.

Using super-resolution confocal and scanning electron microscopy in conjunction with computational analysis to break down the arrangement of S. mutans bacteria and polymers in the plaque, they were able to separate the sticky biofilm layer by layer.

The result was a three-dimensional picture of the specific design of the biofilm.

The researchers found that S. mutans in dental plaque were usually arranged in a mound against the tooth’s surface. They also found other bacteria, such as S. oralis, arranged themselves in a crownlike structure.

Between these layers acting as support and separation was an extracellular scaffold made of sugars produced by S. mutans. This scaffold served to protect and encase the disease-causing bacteria.

Next, the researchers found that the mounds of encased bacteria matched up perfectly with demineralized areas and high acid levels on the surface of the tooth enamel.

Their findings could be the answer to how cavities begin – and provide a path to better treatment.

Source: University of Pennsylvania. ‘Cavity-causing bacteria assemble an army of protective microbes on human teeth.’ ScienceDaily. ScienceDaily, 18 May 2020.