Bacteria in the Mouth, Dental Plaque Biofilms and Health Problems

Hundreds of different types of microorganisms live in the human mouth. These microbes include bacteria, fungi, yeasts, viruses and other creatures. Researchers have found that there are millions of individual bacteria present, most of which are attached to the teeth, the gums, the top and bottom of the tongue and the linings of the mouth and throat. The majority of mouth bacteria live inside a material called a biofilm, which is made of substances produced by the bacteria as well as substances obtained from saliva. Biofilms are found in other areas of the body too, but in the mouth they are known as plaque. Scientists have discovered that bacteria communicate with each other inside biofilms by means of chemical signals.

Normally our immune system prevents mouth bacteria from infecting other areas of the body, and by eating a sensible diet and following careful oral hygiene techniques we can prevent the bacterial population from causing mouth problems. Under some conditions, however, such as when we eat a high-sugar diet, harmful bacteria become more numerous and can cause tooth decay or gum disease. There is also increasing evidence that bacteria in the mouth can spread to other areas of the body. Passages from both the respiratory system and the gastrointestinal system open into the throat, and mouth bacteria may pass into these passages. In addition, some bacteria can pass into the bloodstream through inflamed and bleeding areas on the gums and then invade other tissues.

The mouth environment is a great habitat for bacteria. It’s warm and moist, and receives a frequent source of nutrients when a person eats or drinks. As the bacteria break down their food they produce acids that can damage tooth enamel by causing demineralization. However, saliva contains bicarbonate and other chemicals which help to neutralize the acid, and also substances such as calcium and phosphate that can repair the enamel damage. Saliva also contains antibacterial chemicals, including lysozyme, lactoferrin and lactoperoxidase.

Although the process of tooth decay is a complex process and isn’t completely understood, it’s thought to happen when the rate of acid production by bacteria exceeds the rate of repair by saliva. People with xerostomia, a disorder in which there is a greatly decreased production of saliva, have a very large increase in tooth decay. Some medications also produce a dry mouth and increase the risk of oral health problems.

The tooth decay which is common today (except in people who use good dental hygiene techniques) is believed to be due to the huge increase in fermentable sugars in our diet. Some bacteria produce large quantities of acid as they break down the sugar, and our saliva is often unable to neutralize it all. The most common cause of tooth decay is a bacterium called Streptococcus mutans. Researchers have found that eating sugary foods frequently throughout the day is more likely to cause tooth decay than eating a large amount of sugar at once, or eating sugary foods with a meal.

In addition to damaging teeth, the acid allows mouth bacteria that grow well in an acidic environment to multiply and predominate in the population. Helpful bacteria which limit or change the effects of the unhealthy bacteria are outnumbered and the ecological balance in our mouths is changed by the presence of the sugar.

Plaque is a bacterial colony that may contain several species of bacteria and is colorless, slimy and sticky. The bacteria in the plaque stick to the surface that they have colonized and to each other. The slime protects the bacteria from attack by antibiotics, antimicrobial substances or white blood cells. Rinsing the mouth out with water or mouthwash can remove planktonic (free-living) bacteria but not the bacteria living in the plaque.

Immediately after a dental cleaning chemicals in saliva called glycoproteins collect on surfaces in the mouth, forming a thin layer called a pellicle. The pellicle provides a suitable surface for bacterial attachment. Bacteria begin to form a colony on the pellicle shortly after its formation. Soon the bacteria begin production of the slime, which contains long chains of carbohydrate molecules known as polysaccharides. Plaque also absorbs calcium and phosphorus from saliva.

A healthy mouth contains a different selection or a different proportion of bacteria in the plaque than an unhealthy mouth. People on a high-sugar diet have a higher number of acid-producing and acid-tolerant bacteria in their plaque, such as Streptococcus mutans and species of Lactobacillus.

Physical removal is the best way to remove plaque biofilms. Brushing and flossing are therefore extremely important to clean the surfaces of the teeth and gums. Plaque that has formed in gum pockets needs to be removed by a dental hygienist or dentist. If plaque isn't removed, more minerals from saliva are deposited on its surface and the plaque gradually hardens. It's then known as calculus or tartar, and must be removed in a dental office. Tartar is dangerous because unlike plaque it can't be removed by normal home techniques, allowing the bacteria in the tartar to continue to produce acids. Tartar also causes inflammation and damages gums. Plaque may begin to turn into tartar after only twenty four hours.

Many scientists are studying biofilms, since they are discovering that most bacteria in our bodies live in these films, and they are hard to remove except by physical means. Bacteria in the film coordinate some of their activities by releasing a chemical which acts as a signal to other bacteria. When enough bacteria have released the chemical messenger and the chemical has reached a specific concentration, all the bacteria perform the same action, such as turning on a specific gene. This process of bacterial communication is known as "quorum sensing".

Dental caries (tooth decay), gingivitis (gum inflammation) and periodontal disease (or periodontitis) are the most common health problems caused by mouth bacteria. In periodontal disease, pockets form between the gum and the teeth and become infected by bacteria, which further damage the gum and can destroy bone.

Scientists are now discovering that mouth bacteria can cause problems in other areas of the body. There is evidence that gum disease can lead to heart problems and strokes and may possibly increase the risk of premature births.

People with diabetes are more likely to have periodontal disease than people without diabetes. There is also evidence that once periodontal disease has developed it's harder for diabetics to control their blood sugar. In addition, oral bacteria can cause lung infections and respiratory problems.

To maintain tooth and gum health, most dentists recommend the following steps.

• Eat healthy, low-sugar food choices.
• Limit the intake of acidic food and drinks, such as citrus fruit juices and carbonated beverages, which can cause enamel demineralization.
• Brush the teeth regularly, using good technique.
• Replace toothbrushes frequently, and get a new toothbrush after suffering from a cold.
• Use dental floss to clean between the teeth.
• Don't forget to clean the top of the tongue.
• Rinse the mouth out with water and/or mouthwash occasionally during the day.
• Consider using an antibacterial mouthwash to kill bacteria and a fluoride mouthwash to strengthen tooth enamel. Fluoride also has the ability to kill bacteria.
• Chew xylitol gum, which is antibacterial and enhances the remineralization of tooth enamel. Chewing sugarless gum also increases saliva production.
• Don't smoke. Smoking increases the risk of gum disease.
• Get regular dental check-ups and cleanings to remove any tartar that has formed and to remove bacteria from gum pockets.

These techniques keep bacteria at a safe level, help to remove dangerous invaders, clean and strengthen tooth enamel and clean gums. (Be very careful with xylitol if you have a dog; eating this sugar substitute can lower a dog’s blood pressure to a dangerous level). Even washing the mouth out with water has been found to significantly reduce the level of oral bacteria and is helpful when teeth can't be brushed.