Dental Caries, which is usually known as tooth decay is a non-communicable disease that depends on your diet and the amount of consumption of free sugars. This results in the progress of the acids attacking the enamel which damages the tooth surface over time. It isn’t like a normal infection due to the fact it occurs due to a high sugar diet disrupting the neutral balance of bacteria in the mouth. The bacteria “Streptococcus Mutans” thrives in this sugary environment by feeding on leftover carbohydrates and produces lactic acid as a waste product. This is the reason why the protective minerals of the tooth get dissolved. Even though tooth decay is easily preventable it is still a global issue and is the main cause for tooth extractions in children in the United Kingdom. (there is data in websites and will be shown later) In this essay I will find out why and how “Streptococcus Mutans” is so successful and also how lifestyles and other factors affect the spread and prevention of the disease.
Streptococcus Mutans is a successful pathogen due to its ability to thrive in the high sugar environment. It has evolved to carry three main traits to help it survive, being its ability to synthesise large quantities of extracellular polymers of glucan from sucrose which help it to colonise harder surfaces, also it has an ability to transport and to metabolize the wide range of carbohydrates into organic acids. It can also survive very high stressful environments.
It needs to have a secure hold on the tooths surface since it is at risk of being washed away by the saliva. The S.Mutans synthesises extracellular polysaccharides called glucans from the sucrose providing binding sites for the S.Mutans glucan binding proteins, this promotes bacterial adherence, since the ESP matrix acts as architectural scaffolding for the structure. This tough layer formed is called dental plaque. This protects the enamel from any outside interference.
When the plaque is formed the S.Mutans is feeding on leftover carbohydrates and relies fully on glycolysis for its respiration since the layer lacks oxygen it has to anaerobically respire. With the main waste product of glycolysis being lactic acid and since the thick biofilm prevents the saliva from washing it away, it traps the acid underneath the plaque.
You would expect the S.Mutans to be destroyed due to the highly acidic environment but as we mentioned earlier it has a F-ATPase system which is a protein pump which pushed H+ ions out of the cytoplasm to maintain neutral pH. So it can stay in the plaque and keep metabolising sugars so it can out compete non- acid tolerant bacteria.
If this continues the lactic acid has nowhere else to go but destroy the tooth structure, even though enamel is made out of a strong structure with a pH threshold of 5.5 in which the acid goes below. When the H+ ions react there is a loss of calcium and phosphate ions which dissolve, weakening the structural integrity of the tooth, which forms the holes called cavities.
The most common way of it being transmitted is through vertical transmission, so new born babies are born with a sterile oral cavity, they will obtain the pathogen via their mother through vertical transmission. Vertical transmission occurs through saliva sharing like using the same utensils.
Since S.Mutans cannot stick to the gum it needs to stick to the enamel it can only form its bacterial colony during the “window of infectivity” which is when the baby starts getting its first baby teeth, around 6 months after birth. Even though S.Mutans is highly infectious and easily transmittable between people, it will not be an issue unless triggered by a diet containing high free sugar intake.
Due to children being vulnerable to the disease at such a young age due to their high consumption of sugary sweets and drinks it becomes the perfect environment for the bacteria to thrive. The decay is worse in children's teeth than adult teeth since they contain less minerals and have a thinner layer of enamel. This helps to understand why dental caries is the most common reason for hospital admissions in the UK for young children (ages 5-9) with 21,162 children from 2024-2025 in this age range being admitted to hospital with it slowly rising from 2023-2024.
Dental Caries is recognised as the most common non-communicable disease creating a financial and clinical burden in healthcare systems in 2019. Oral diseases including Dental Caries affect close to 3.5 billion people. With peaks from the ages in childhood and early teenage years.
There is a strong contrast between different economic levels. With people from areas with social deprivation having a greater rate of decay and tooth loss. This is not due to biological factors but due to lower income they could only afford sugar-dense food and also limited access to better healthcare, this led to a higher amount of cavities in these communities. The public health survey highlights a financial divide with children from deprived areas having oral decay two times more than less deprived areas, as it is left untreated for longer. Consequently dental caries still stays as the leading cause of hospital admissions for tooth extractions in younger children.
If you wondered how to prevent the disease, the NHS divides it into 2 sections. The first section covers prevention to stop early tooth decay, and the second section focusing on treating advanced tooth decay which is repairing any tooth damage.
Primary prevention focuses on application of fluoride through toothpaste, this helps to strengthen tooth enamel by substituting OH- for F- which is more stable and resistant to acid and helps lower the critical pH to 4.5 from 5.5. It is also recommended to reduce the intake of dietary free sugars. Also on your back molars a fissure sealant is applied which is a smooth barrier to stop the buildup of bacteria and food .
Secondary prevention is used when the demineralisation process affects your tooth by going into the enamel and creating a cavity. Primary prevention cannot be used and since the bacteria is now inside the tooth you need to use dental drills to excavate the dental tissue. The hole in your tooth is now filled using synthetic biomaterials usually using resin or amalgam. Yet in some cases if the bacteria is left untreated it can reach the root canal which requires surgical extraction to prevent worse infection.
SOURCES:
https://pmc.ncbi.nlm.nih.gov/articles/PMC6615571/
https://www.who.int/news-room/fact-sheets/detail/oral-health
https://www.nhsinform.scot/illnesses-and-conditions/mouth/tooth-decay/
https://digital.nhs.uk/data-and-information/publications/statistical/children-s-dental-health-survey/child-dental-health-survey-2013-england-wales-and-northern-ireland
https://www.rcseng.ac.uk/news-and-events/media-centre/press-releases/dental-stats-sept-25/
https://www.gov.uk/government/collections/oral-health