Dental plaque (AKA biofilm): What *exactly* is it?

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Did someone say biofilm? It may sound like something from a sci-fi movie, but biofilm can occur almost anywhere. Biofilms are communities of microorganisms (like bacteria and fungus), held together by a slimy, glue-like substance.

An instance of a biofilm in nature is the slippery coating you sometimes find on rocks in a flowing stream. A prime example in humans is dental plaque. It can also be called dental biofilm, oral biofilm, or dental plaque biofilm. The question is how does biofilm affect your oral health and what can you do about it. Let’s find out.

What causes dental plaque in the first place?

As we mentioned before, a biofilm is a colony of microorganisms that come together under a clear, sticky layer. Dental plaque is one of the most common examples of biofilm. (You know that furry teeth feeling?) While you might think ‘oh, I don't have biofilm’, the truth is that most people unknowingly have it in their mouth.

In any environment where there is moisture, microorganisms (bacteria, and fungi among others) and a surface (this can be teeth, dentures, crowns, and implants), biofilm can exist. 

Studies have shown that the human mouth is home to a diverse community of more than 700 species of bacteria. So, it’s not surprising that research has found over 600 species of bacteria, as well as other resident organisms, in an individual sample of dental biofilm. 

Certain species of microorganisms are more commonly associated with advanced periodontitis (p. gingivalis, aggregatibacter actinomycetemcomitans, tannerella forsythia). Whereas, streptococcus mutans (a type of bacteria found on most tooth surfaces) are more often associated with dental caries (AKA tooth decay). However, there’s less need to worry about the different species of bacteria, than there is to keep your mouth clean.

Biofilm doesn’t only develop in adolescents and adults. It can be found in babies' mouths too, even before their teeth appear. How often have you seen a baby drop its dummy on the floor and its mum pick it up, pop it in her mouth and then return it to the baby’s mouth? Similarly, mums may use their tongue to test if the food on their baby’s spoon is too hot. Both well-meaning actions introduce bacteria from their mouth into their baby’s mouth, where it can form a biofilm.

How does dental plaque (biofilm) form?

We’ve explained what biofilm is, but you’re no doubt wondering what triggers biofilm development. The best way to understand this is to look at the stages of dental plaque formation.

Illustration of how biofilm is formed.
Dental plaque is made up of different microorganisms, many of which already live in the mouth. Biofilm begins when groups of bacteria attach to a surface in the mouth (teeth, gums, dental implants etc).

Stage 1 Adsorption of molecules

A conditioning surface film, known as dental pellicle, forms. This happens within minutes after tooth eruption, teeth cleaning or chewing. This substance is crucial to biofilm formation, as it provides the initial surface for microorganisms to attach to. 

Stage 2 — Bacterial adhesion

Bacteria stick (adhere) to the conditioned  surfaces, with some species of bacteria adhering better than others.

Stage 3 — Cellular growth

The bacteria multiply and the overall biofilm mass grows. The extracellular matrix (the sticky glue-like substance) also increases. 

Stage 4 — Maturation

The microbial makeup of the biofilm now becomes more complex with a growing number of new disease-causing bacteria. As the biofilm layers increase, so too does the pocket depth and the risk of gingival inflammation and periodontitis.

The effect of dental plaque biofilm on oral health

Under certain conditions, dental plaque hardens and forms tartar (dental calculus). Tartar is rough and porous, making it the perfect host for more harmful bacteria. The bacteria in biofilm also produce acid. This can erode the tooth enamel, leading to cavities.

Under certain conditions, dental plaque hardens and forms tartar (dental calculus).
When gums are inflamed (in the case of gingivitis and periodontitis), bacteria from the dental plaque can enter the bloodstream. This enables them to travel to other parts of the body. 

Problems associated with plaque can  include bad breath (halitosis), gingivitis, and periodontitis. Inflammation is the body's way of fighting bacteria. In some cases, inflammation can damage the ligaments and bone that support the teeth. This can cause tooth loss.

Yet, the negative effect of biofilm goes beyond oral health. When gums are inflamed (in the case of gingivitis and periodontitis), bacteria from the dental plaque can enter the bloodstream. This enables them to travel to other parts of the body. Bacterial biofilms have been linked to numerous health issues in other areas of the body. This includes conditions, such as stroke and cardiovascular disease.1  

But here’s the thing. As more bacteria join forces to form a biofilm, they become stronger and more resistant to common antibiotics. In fact, the microorganisms in plaque are 1000 times more resistant to antibiotics than free floating bacteria.2 It is much more effective to remove it with a toothbrush or interdental cleaning device such as an interproximal brush or floss. Not only for the good of your oral health, but for your general wellbeing also.

Keeping dental biofilm at bay

While scientists are still trying to understand biofilm, there’s no doubt that preventing dental plaque build up is a must. Here are some effective ways to manage dental bacterial plaque.

Young woman brushing teeth preventing dental plaque buildup.
Knowing where dental plaque often forms can help with its removal. Pay attention when cleaning in between the teeth, at the gum line, at filling margins, and where teeth overlap.

Know where it hides

Dental plaque will form anywhere it has a chance to. Everyone gets plaque in reasonably similar amounts, but some people are better at cleaning it off. Knowing where it often forms can help with dental plaque removal. Pay attention when cleaning in between the teeth, at the gum line, at filling margins, and where teeth overlap. 

Practise good oral hygiene

Brushing twice a day with a fluoride toothpaste can help reduce the amount of plaque that forms on the teeth. However, dental biofilm tends to form in the places that are difficult to clean. We know that brushing alone reaches only about 60% of the tooth area. Interdental brushes are an effective way to combat this problem. Available in different sizes, they fit between the gaps in your teeth. This makes it easier to dislodge the bacterial biofilm from areas of the mouth a toothbrush can’t fit. 

Regular dental check-ups

Bacterial regrowth and dental biofilm formation can happen in as little as a few hours after brushing your teeth. Once it has matured, plaque biofilm sticks like glue. Ideally, you are able to control plaque development yourself, independently. Like a sporting coach, your periodontist and dental hygienist should give you feedback on your technique and help you address the areas that you are missing. In case you do miss some, your periodontist and dental hygienist have the skills and experience to effectively remove bacterial dental plaque from hard-to-reach places.

A regular dental visit can also spot any problems associated with dental plaque early—before they progress. This is especially important for people with periodontitis. Controlling plaque biofilm controls the inflammation, which can potentially lead to tooth loss.

Final thoughts…


Dental biofilm is always lurking. The only way to keep it under control is with mechanical removal (brushing and interdental cleaning) and regular professional teeth cleaning. Mouth rinses and water flossers are relatively ineffective at removing dental plaque. This is because they can’t break down the strong matrix of microorganisms.   

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