Casey Best

Running Head: DENTAL CARIES 1

Streptococcus mutans

Introductory/Background 2

Streptococcus mutans is a facultative anaerobic, gram-positive, non-motile bacteria belonging to the streptococcaceae family. S. mutans contains a thick cell wall composed of peptidoglycan which contains sugars and amino acids. There are many different conditions in the mouth, but carbohydrates are motivators for this bacterium that produces lactic acids, thereby lowering the pH in the mouth and creating an acidic environment. Due to the ability of S. mutans to survive in a low pH environment and up to 104 degrees Fahrenheit, eroding of tooth structure, known as tooth decay, can begin. Fuel for metabolism lacks because of the absence of oxygen; therefore, it is mostly found in the deep crevices of teeth or in the pit and fissures, also known as the biting surfaces.

“S. mutans was first described by James Kilian Clarke (1886-1950) after he isolated it from a carious lesion, but it was not until the 1960’s that real interest in the microbe was generated when researchers began studying dental caries” (Akhaven, 2014). S. mutans was re-identified in infection of animal rodents. All of Koch’s postulates were tested in animal models, but it was difficult to establish that it was also a human dental pathogen until samples were taken from a decomposed tooth site showing a phenomenal connection between S. mutans and decay. Historically, cavities were characteristic to the general overgrowth of oral bacteria, termed the “non-specific plaque hypothesis”, meaning only certain bacteria are responsible for causing tooth decay. In 1960, however, Paul H. Keyes from the National Institute of Dental Research compared the bacteria makeup of caries active and caries in-active in hamsters and found a much higher percentage of a group of bacteria termed “Streptococcus mutans“.

This pathogen occurred during a time period in which people depended on foods that were enriched in carbohydrates, and this most likely contributed to the first appearance of dental caries. Tooth decay did not become an important health problem until sucrose became a major ingredient in the foods we eat today. “In fact, studies show that as much as one-half of a pound of sucrose consumed daily at meals for two years was not associated with an increase in dental decay; however, when the same or lesser amounts of sucrose were ingested between meals, subjects developed new decay at the rate of about three to four tooth surfaces per year” (Loesche, 1996). Although the need for certain bacteria to turn milk into yogurt and cheese was not known by early farmers, today we know that some species of bacteria keep our mouths healthy; however, S. mutans is not one of them. It is, in fact, one of the worst offenders against healthy teeth. The bacteria in the pots of yogurt weren’t the only thing developing – so were the microbes in our mouth.

“Twisted berry” is the term that may be used when referring to Streptococcus, because of the resemblance to a string of beads when looking through a microscope. “Streptococcus mutans is a specialized microorganism equipped with receptors that allow it to adhere to the surface of the tooth creating a slimy environment. After adherence to the tooth, S. mutans begin to divide and produce micro-colonies within the slime layer to construct a biofilm” (Microbe Wiki, 2016). When a biofilm is formed, S. mutans begin to make dextran, which is made up of many glucose molecules that allow it to bind to the enamel and enable S. mutans to attach sucrose and glucan-sucrose together. As a result, these products produce fructose, which allows energy for bacteria. Biofilms produce extracellular polymeric substances, which are mostly made up of polysaccharides and proteins that colonize a surface.

Clinical Significance

Bacteria are a large part of the human mouth’s ecosystem. The 6 billion bacteria that one mouth can hold are constantly in the process of multiplying, finding places to live, or dying. S. mutans is a heterotrophic organism, which means that it lives by getting its energy through consuming organic matter from other organisms, living or deceased, and making the human mouth the host. There are safe places in your mouth and unsafe places, and the unsafe places consist of pathogenic bacteria that can cause tooth decay, gum inflammation, and tooth loss. The mouth contains good bacteria and bad bacteria, which is known as Streptococcus mutans, and as much as 90% of the world is affected by this infamous microbe.Since its discovery by Clarke, S. mutans has become one of the most well-known organisms. As the world continues to consume more refined sugars, we fuel the production of acids for colony growth, which leads to the formation of dental plaque. If plaque develops on teeth, it can turn into tarter, and tarter is much more difficult to remove from the teeth than plaque. Plaque is a soft, sticky substance that contains bacteria, but it can easily be brushed off before it turns into tarter, which is a hard non-sticky substance. Tartar has to be removed by a dental hygienist or dentist, and because it is rough, it makes it easier for bacteria to attach to the teeth.

The enamel is the hard outer layer of the tooth, and this hard layer protects the tooth against decay. Dental cavities are holes in the first two layers of the tooth, which are the enamel and the dentin, and once this disease has developed, it requires treatment almost immediately. A cavity will only grow larger and eat away at the tooth if left untreated, which can cause excruciating pain and may also cause bad breath. Dental caries has become one of the most widespread diseases in humans today and has negatively affected a multitude of people worldwide.

Billions of dollars are spent each year on treating dental caries. The longer one waits to get a cavity filled, the more expensive and painful it will become. Not only will the teeth become extremely painful, the jaw will most likely be affected as well. Plaque buildup can also lead to gum disease called gingivitis, which causes tender and swollen gums that sometimes bleed. Gingivitis is a milder form of gum disease that can be treated with proper brushing and flossing; however, if it progresses untreated, severe periodontal disease can develop. Gum tissue will begin to pull away from the teeth and bacteria will start to destroy the underlying bone supporting the teeth, and this will most likely result in the loss of one or several teeth.

S. mutans can also cause dangerous, life threatening infections. Tooth decay can spread in the mouth and completely destroy the teeth if not properly treated, and in the most extreme cases, can even lead to death. Cardiovascular problems, which are major contributors to early death in American men and women, can also develop as a result of this type of serious infection. Once this bacterium migrates into the bloodstream and arteries, it causes blood clots and restricts oxygen and blood flow. Although it has not yet been proven that gum disease causes cardiovascular issues, evidence exists that points to gum disease as a possible culprit. Healthy gums should be firm and a light pink color, but if gums are red or swollen, or if they bleed after flossing, it is time for a checkup with the dentist. This pathogen can travel from one person to the next via horizontal and vertical transmission. “Some people are genetically more prone to periodontal and gum disease than others. So if it runs in your family, you should be especially vigilant” (Griffin, 2005).

A person that has dental caries may not even be aware that he or she has the disease because it cannot necessarily be seen with the naked eye and may not always be painful. The earliest sign of a cavity forming is a chalky white spot on the surface of the tooth that does not cause pain. If demineralization continues, the white spot may turn brown, which most likely represents a cavity. Once the nerves of the tooth are exposed, the tooth will become very sensitive to heat, cold, and sugary foods, and unbearable pain will ensue. Once the cavity has formed, the tooth structure can’t regrow. Additionally, because of the pain, the ability to eat, sleep and function well is limited, and quality of life suffers.

Preventative/Treatment

Prosthetic devices are also a favorable environment for Streptococci, but the ” American Heart Association has reduced its recommendations on pre-medicating before a dental procedure, including those who only have pacemakers, prosthetic heart valves, a history of endocarditis, heart transplants or certain heart defects to pre-medicate, since they are at greater risk for infection” (American Heart Association, 2016).

When a tooth is weakened by internal decay, the tooth could fracture while chewing foods. If that happens, most of the time the tooth can be saved, but in some cases, an extraction of the tooth will be done if it is not salvageable. Although S. mutans does not have a vaccine, there are other preventable measures you can take to stop this bacterium before it causes damage.

S. mutans is a natural bacterium in our body, so everyone has it, although not everyone is at the same risk. Learning how to control it will help prevent these bacteria from taking over. Brushing the teeth twice a day with fluoride toothpaste will help reduce the decay rate, especially after eating foods and drinks that are high in sugars. Additionally, fluoride is a mineral that helps prevent cavities from forming. It replaces mineral loss in the enamel and reduces the ability of the bacteria to make an acid. Many dentists also recommend using a mouth rinse with fluoride for those at higher risks of developing this disease. When brushing the teeth, only the front and back surfaces of the teeth can be reached, so flossing is extremely important and highly recommended to reduce accumulations of bacteria that thrive in the crevices between the teeth that a toothbrush cannot reach. Flossing will also help reduce the possibility of developing gum disease in the first place.

“More than 50 years ago, examinations of people entering the military showed that Americans’ teeth were in pretty bad shape. At that time, few people took good care of their teeth, and there were no guidelines for how often one should see a dentist. Many dentists focused on fixing problems rather than preventing them” (Colgate-Palmolive Company, 2014). Even if one is taking good care of one’s teeth at home, it is still recommended to regularly see a dentist twice a year. Some people may even need to be seen more often depending on their oral hygiene, habits and medical conditions. The dentist is able to check for problems that may not be painful or in sight; moreover, x-rays are used to help the dentist diagnose problems before they become a major concern as they allow the dentist to see inside the tooth and surrounding tissue.

Dental sealants are an invisible plastic coating that bonds to the tops of the teeth, filling in the pits and fissures and making them a powerful weapon against decay. They are typically applied to children’s teeth because this gives them more protection throughout their cavity-prone years; however, adults who do not have decay present would also benefit from sealants on their back molars, which are difficult to reach in the mouth with a toothbrush. To fix a cavity caused by S. mutans, the most common procedure a dentist will use is to remove the decay and fill that area with composite or amalgam filling. The difference between the two fillings is that amalgam is cheaper and also more durable; however, it is made with zinc, copper, mercury and tin, and it can easily cause discoloration of the tooth as well as cracks and fractures. Composite is a made with plastic and fine glass particles, and it comes in different shades to easily match one’s tooth. Additionally, since it is chemically bonded to the tooth, it provides better support; however, it cannot withstand the chewing forces as long as amalgam can. In extreme cases, a root canal and crown may be placed after the decay is removed by simply removing the roots of the tooth and placing a cap over the coronal portion of the tooth, but if the decay exceeds a certain level, the dentist may have to remove the entire tooth.

Fighting Streptococcus mutans is a constant battle, and the most important weapon we have in the fight against its progress is knowledge. By practicing healthy habits and eating a balanced diet, along with taking proper care of our teeth and visiting the dentist regularly, we can all win the battle against gum disease and keep our teeth for a lifetime.

References   

Akhaven, K. (2014, October 19). Streptococcus mutans. Retrieved from MicrobeWiki: https://microbewiki.kenyon.edu/index.php/Streptococcus_mutans.

American Heart Association. (2016, October 10). Infective Endocarditis. Retrieved from American Heart Association: http://www.heart.org/HEARTORG/Conditions/CongenitalHeartDefects/TheImpactofCongenitalHeartDefects/Infective-Endocarditis_UCM_307108_Article.jsp#.WNPItU11qUk

Colgate-Palmolive Company. (2014, May 7). How Often Should You Go to the Dentist? Retrieved from Colgate Oral Care Center: http://www.colgate.com/en/us/oc/oral-health/basics/dental-visits/article/how-often-should-you-go-to-the-dentist

Griffin, M. R. (2005, April 6). Your Guide to Gum Disease Symptoms and Heart Disease. Retrieved from WedMD: http://www.webmd.com/heart-disease/features/your-guide-gum-disease#2

Loesche, W. J. (1996). Microbioligy of Dental Decay and Periodontal Disease. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK8259/

Microbe Wiki. (2016, February 11). Streptococcus mutans- Tooth Decay. Retrieved from MicrobeWiki Website: https://microbewiki.kenyon.edu/index.php/Streptococcus_mutans-_Tooth_Decay

Streptococcus mutans. (2014, October 19). Retrieved from MicrobeWiki: https://microbewiki.kenyon.edu/index.php/Streptoccus_mutans