Plaque is made up of invisible masses of harmful germs that live in the mouth and stick to the teeth.

• Some types of plaque cause tooth decay.
• Other types of plaque cause gum disease.

Red, puffy or bleeding gums can be the first signs of gum disease. If gum disease is not treated, the tissues holding the teeth in place are destroyed and the teeth are eventually lost.

Dental plaque is difficult to see unless it’s stained. You can stain plaque by chewing red “disclosing tablets,” found at grocery stores and drug stores, or by using a cotton swab to smear green food coloring on your teeth. The red or green color left on the teeth will show you where there is still plaque—and where you have to brush again to remove it. Stain and examine your teeth regularly to make sure you are removing all plaque. Ask your dentist or dental hygienist if your plaque removal techniques are o.k.

Our teeth are moistened with saliva produced by various salivary glands in the mouth. Healthy saliva has a neutral pH and and electrolyte composition that resembles that of plasma with an increased abundance of phosphate and a few other ions. It also contains larger molecules that form mucus, enzymes, antimicrobials and other substances. Among those, some glycoproteins can bind to the exposed surface of enamel. They form a protective film, called dental pellicle, attached to the crown of each tooth. The pellicle is removed with tooth brushing but it forms again moments after the clean tooth makes contact with saliva.

Human saliva is also populated by microorganisms, including dozens of species of bacteria, fungi and archea. Most of them ferment dietary sugars and produce lactic acid. They can bind to the glycoproteins of the pellicle and remain attached to the tooth.

Do you know what’s in your mouth? It’s home to about 700 species of microbes. These include germs like bacteria, fungus, and more.

“Everybody has these microbes in their mouth,” says Dr. Robert Palmer, an NIH expert on oral microbes.

Some microbes are helpful. Others can cause problems like tooth decay and gum disease. Troubles begin when microbes form a sticky, colorless film called plaque on your teeth.

Brushing and flossing help to keep your mouth clean. But after you brush and floss, germs grow again and more plaque forms. That’s why you need to clean your mouth regularly.

Community Growth

Different microbes grow in different places. Some stick to your teeth. Others prefer your tongue. Some lurk in the tiny pockets between tooth and gum. Once they’ve found their homes, they form diverse communities with the other germs.

Mouth microbes work together to protect themselves with a slimy, sticky material called a matrix. The matrix in plaque makes it harder to remove it.

The communities within the matrix include both helpful and disease-causing microbes. The good microbes help keep the growth of bad microbes in check. Good microbes also help you digest food and can protect against harmful microbes in food.

Certain things you may be doing can help bad microbes grow better than the good ones. Sugary foods and drinks feed some microbes and help them increase in number and spread out.

Some of these sugar-loving microbes can turn sugar into matrix and acid. The acid destroys the surface of your teeth. The more sugar in your diet, the more fuel is available for these microbes to build up plaque and damage teeth.

“It’s more productive to think about the community than it is to think about the single microbe that causes disease,” Palmer explains.

You can’t stop tooth decay by getting rid of just one type of acid-making microbe. There are several different types of microbes in the plaque that make acid.

The good news is that limiting sweets and brushing and flossing regularly can help prevent bad microbes from growing out of control.

Helpful Neighbors

“Many bacteria in our mouths depend on help from other members of their community to survive and prosper,” says Dr. Floyd Dewhirst, a dental expert who studies microbes at the Forsyth Institute.

Because microbes grow in communities, it’s important to understand how both helpful and harmful microbes work. Dewhirst’s team is trying to identify all the different germs living in the mouth and what they do.

Before the team can study a microbe, they have to figure out how to grow it. The challenge is that some microbes don’t like to grow anywhere but in your mouth. About 30% of the 700 species haven’t been grown in the lab yet.

Dewhirst’s team is working on growing those microbes in the lab that no one has grown before. They’re using genetic and other information to identify each one and learn more about them.

“The question is,” he says, “once you know who is there and have a quick way of identifying them, what are all of these bacteria doing?”

Dewhirst’s studies have shown that some microbes make certain substances that help their neighbors grow. His team is trying to identify what those substances are.

They also want to find out how these microbes may affect people’s health. Being able to grow microbes in the lab lets scientists run tests to figure out how they’re involved in health and disease. This information could one day help scientists come up with better ways of preventing and treating oral diseases.

Partners in Decay

An important health problem caused by mouth microbes is early childhood tooth decay. “In the U.S., about 23% of our children between the ages of 1 and 5 are affected by this disease,” says Dr. Hyun (Michel) Koo, a dental researcher and oral health expert at the University of Pennsylvania.

Tooth decay can get worse very fast. The microbe matrix and acid from bacteria are thought to be the main cause of tooth decay in young kids.

Koo’s team has found that there’s also fungus in the plaque of kids with rampant tooth decay. The fungus partners with the matrix- and acid-making bacteria to worsen tooth decay.

“Bacteria by itself can cause tooth decay,” Koo explains. “But when fungus is there, it boosts up the entire machinery.”

Koo’s team has shown that some fungus can get energy from sugar that bacteria release while making acid. The fungus then releases substances that feed the bacteria’s growth. This helps the bacteria form an even tougher matrix and make more acid.

Busting Plaque

Koo’s team is looking for new ways to fight plaque buildup and tooth decay. They’ve developed tiny substances, called nanoparticles, that are small enough to get inside and destroy the matrix that protects microbes. The nanoparticles can also kill the acid-making bacteria without harming good bacteria in the mouth.

Koo’s team has shown that these tiny substances can reduce acid damage to the tooth surface. The researchers hope to test the approach in people in the future.

Nanoparticles are just one approach now being studied to prevent or treat mouth diseases.

Future technologies may help keep our mouths healthier. But there are many things you can do to keep bad mouth microbes in check now. See the Wise Choices box for some tips. You can’t have a healthy body without a healthy mouth.

Keep Mouth Microbes in Check

These tips can help prevent tooth decay and mouth infections:

• Brush your teeth with a toothpaste that contains fluoride.
• Floss away the plaque between your teeth.
• Don’t forget to brush your tongue.
• Limit sugary foods and drinks.
• Drink fluoridated water. Learn about fluoride levels in your water (CDC).
• Get regular dental exams and professional cleanings.

When microorganisms grow attached to a surface, they may also secrete a sticky extracellular matrix that further stabilizes them in place. This forms a biofilm, a thin layer of microorganisms + extracellular matrix. Dental plaque is biofilm that forms on the surfaces of the crown, along the gumline, or within the gingival sulci.

The bulk of the microorganisms that form the biofilm are Strepcoccus mutans, Fusobacterium and Actinomyces. Streptococcus and other anaerobes are the initial colonisers of the pellicle and play a major role in the establishment of the early biofilm community. As more microbes attach and secrete matrix, the plaque becomes thicker. The substances secreted by them gradually alter the chemical environment within the plaque and this favors the establishment of new types of microorganisms, called the later colonizers.

The bacterial equilibrium position varies at different stages of formation. Below is a summary of the bacteria that may be present during the phases of plaque maturation:

• Early biofilm: primarily Gram-positive cocci
• Older biofilm (3–4 days): increased numbers of filaments and fusiforms
• 4–9 days undisturbed: more complex flora with rods, filamentous forms
• 7–14 days: Vibrio species, spirochetes, more Gram-negative organisms

Early colonizers

Most genera listed below include multiple species that form plaque.

• Streptococcus (60-90% of bacteria in plaque)
• Eikenella
• Haemophilus
• Prevotella
• Priopionibacterium
• Capnocytophaga

Late colonizers

• Actinomyces
• Prevotella
• Eubacterium
• Treponema
• Porphyromonas

Fusobacterium is another very common group of colonizers that appears between the early and late colonisers, linking them together.

Environment

The warm and moist environment of the mouth and the presence of teeth, makes a good environment for growth and development of dental plaque. Teeth make great settlement surfaces for the biofilm. Unlike other parts of the body, tooth surfaces are firm and non shedding. The main ecological factors that contribute to plaque formation are pH, saliva, temperature and availability of oxygen. The normal pH of saliva is neutral and plaque flourishes at pH 6.7 to 8.3. Variation in pH within the mouth favors the development of specific types of microorganisms in plaque. Saliva acts as a buffer maintaining the pH in the mouth between 6 and 7. The normal temperature of the mouth ranges between 35 °C and 36 °C, and a two-degree change has been shown to drastically shift the dominant species in the plaque. Oxidizing reactions are carried out by aerobic bacteria. Their metabolism influences the oxygen levels in plaque and affects the composition of its microbial community.

The microorganisms in plaque are normally unable to harm the teeth. They attach to the pellicle and grow at a moderate speed forming a thin plaque. The lactic acid that they secrete diffuses easily into the saliva where it is buffered and it does not affect the enamel which is protected by the pellicle. Most of the cover of pellicle and plaque is removed daily at each event of tooth brushing and flossing. Plaque is therefore present most of the time, but is it prevented from growing thick.

The first kind of plaque to form after the teeth are brush is supragingival biofilm, which is a dental plaque that forms above the gingiva. It is most common between the teeth, in the pits and grooves of the teeth and along the gums. It is rich in aerobic bacteria but if allowed to grow thick, anaerobic bacteria may dominate its composition.

Plaque located under the gums is called a subgingival biofilm. It follows the formation of the supragingival biofilm which grows along the dentogingival attachment line until it manages to bypass it. The subgingival biofilm is mostly made of anaerobic bacteria. As this plaque attaches in a pocket under the gums, it is less exposed to oxygen.

Gingivitis is the most common result of plaque build-up around the gingival tissues. The bacteria found in the biofilm secrete acids and proteolytic enzymes that cause a localized inflammation of the tissue. This is characterized by a red, puffy appearance of the gums and bleeding during brushing or flossing. Gingivitis due to plaque can be resolved by removal of the plaque. If left for an extended period of time, however, the inflammation may begin to affect the periodontal ligament, in a progression referred to as periodontitis.

In periodontitis, bacteria in plaque release enzymes that attack not only the collagen but also the bone. At the same time, osteoclasts in the bone erode it to prevent further infection. This can be treated with brushing and cleaning in between the teeth as well as with surgical debridement (removal of decayed tissue).

Caries is an infectious disease caused primarily by Streptococcus mutans, characterized by acid demineralization of the enamel and deeper dental tissue. When the plaque becomes very thick, saliva is unable to penetrate and cannot neutralize the acid produced by the bacteria. These acids then lead to demineralization of the tooth surface.

There are two main methods of detecting dental plaque in the oral cavity: visually or through the application of a disclosing gel or tablet.

Dental plaque may present as a yellow, tan or brown stain on the tooth. It can be detected thorough contact as a rough surface and it collects in the instrument if the tooth is scraped. The most common areas where plaque is found is between the teeth and along the cervical margins.

Disclosing agents are applied to the teeth and stain the tooth with one or multiple colors to indicate the amount, location and age of plaque build-up. Clean surfaces of the teeth do not retain the disclosant after the mouth is rinsed, but surfaces covered in plaque do. Plaque disclosing agents are available for use at home or in the dental clinic. These gels provide a visual aid in the management of dental plaque.

Calculus is a form of hardened dental plaque. It is caused by precipitation of minerals from saliva in plaque on the teeth. This process of precipitation kills most bacteria within dental plaque, but the rough and hardened surface that is formed provides an ideal surface for further plaque formation. Calculus buildup compromises the health of the gingiva (gums) and teeth.

Heavy staining and calculus deposits exhibited on the lingual surface of the mandibularanterior teeth, along the gumline.

Like plaque, calculus can be supragingival or subgingival. It should be removed mechanically but brushing and flossing are not effective because it is more firmly attached to the tooth than plaque. Calculus buildup has to be removed at the clinic with dental hand instruments or with an ultrasonic scaler.

Calculus is composed of about 50% inorganic (minerals) and 50% organic (cellular and extracellular matrix) components. The mineral part consists of various forms of calcium phosphate crystals. The organic component is approximately 85% microorganisms and 15% extracellular matrix. The cells are primarily bacterial, but also include at least one species of archaea (Methanobrevibacter oralis) and several species of yeast (e.g., Candida albicans). The organic extracellular matrix in calculus consists primarily of proteins and lipids (fatty acids, triglycerides, glycolipids, and phospholipids).

Good oral health helps you enjoy life. It lets you: speak clearly; taste, chew, and swallow delicious and nutritious foods; and show your feelings through facial expressions such as smiling.

If you protect your oral health with good oral hygiene practices (brushing and flossing), the odds are in your favor you can keep your teeth for a lifetime.

Brush Your Teeth

To keep your teeth healthy, it is important to remove dental plaque, a sticky, colorless film of bacteria. Plaque buildup can cause tooth decay and gum disease.

Even teeth that already have fillings are at risk for tooth decay. Plaque can build up underneath a chipped filling and cause new decay. And if there are areas in your mouth where your gums have pulled away from the teeth (called gum recession), the exposed tooth roots can decay as well.

Dental plaque is hard to see. You can see it more easily if you stain it. After you brush your teeth, chew “disclosing tablets” (which you can buy at a drug store), or brush with a special disclosing toothpaste. The color will show you where there is still plaque, and you can then brush those areas again to remove it. (Parents – Disclosing tablets can also be very helpful for teaching children how to do a good job brushing their teeth!)

Brushing tips:

• Use fluoride toothpaste. Fluoride is what protects teeth from tooth decay (cavities). It prevents decay by strengthening the tooth’s hard outer surface, called enamel.
• Angle the bristles toward the gumline, so they clean between the gums and teeth.
• Brush gently using small, circular motions. Do not scrub hard back and forth.
• Brush all sides of each tooth.
• Brush your tongue.

And, remember to replace your toothbrush when the bristles become frayed.

Clean Between Your Teeth

Cleaning between teeth to remove plaque is also part of a good oral hygiene routine. If plaque is not removed, some of it can harden below the gum line and irritate the gums. The gums become red, swollen, and may bleed easily. These are signs of gingivitis. Gingivitis is a mild form of gum disease, and you can usually reverse it with daily brushing and flossing.

If plaque stays on your teeth for too long, it can harden. This hardened plaque is called calculus, or tartar. The only way to remove tartar is to have your teeth cleaned by a dentist or dental hygienist. If the tartar is not removed, the gingivitis can get worse and lead to more severe gum (periodontal) disease. In advanced stages, gum disease causes sore, bleeding gums; painful chewing problems; loose teeth; and even tooth loss.

Floss to remove plaque, and food particles, from between your teeth.

Flossing tips:

Some people find flossing difficult because of arthritis or other issues. If it’s too hard to hold floss, try a plastic or wooden dental pick or one of these:

Helpful Tips

Follow these tips to keep your teeth and gums healthy:

• Brush your teeth twice a day with a fluoride toothpaste.
• Clean between teeth regularly to remove plaque. Use dental floss or a special brush or wooden or plastic pick recommended by a dental professional. Or try a floss holder, floss threader, or water flosser.
• Visit the dentist for routine check-ups and professional cleaning.
  • If you are at a higher risk for tooth decay (for example, if you have a dry mouth because of medicines you take), your dentist or dental hygienist may give you a fluoride treatment, such as a varnish or foam during the office visit. Or, the dentist may recommend a fluoride gel or mouth rinse for home use.
  • If you are at higher risk for gum disease because of a medical condition (for example, diabetes), your dentist may want to see you more frequently.
• Drink fluoridated water. Drinking water with the right amount of fluoride protects your teeth throughout the day.
• Don’t smoke. Smoking increases your chance of gum disease.
• If you are planning to become pregnant, have a dental checkup. Because of hormonal changes, pregnant women may develop gingivitis and experience gums that are swollen and bleed easily. During pregnancy, it is especially important to practice good oral hygiene to maintain the health of your gums.
• Eat a well-balanced diet. Limit sweets and sugary drinks, such as soda.