Dental caries is another name for tooth decay, which affects many people during their lifetime. Commonly dentists advise measures such as regular brushing and flossing to prevent the development of the caries in the first place, but fillings are usually necessary once the decay has produced a hole in the teeth. A collection of strains of a bacterial species called Streptococcus mutans are responsible for the decay in the majority of cases, and scientists think that a vaccination may help the body to combat these bacteria before they manage to produce decay. As of January 2012, a caries vaccine is still under research and is not in regular usage, due to questions about effectiveness and safety.
Teeth are made from several components, but the outside layer, which is called the enamel, is very hard and resistant to damage. Caries can arise, however, when food and saliva mix with bacteria and attach on to the outside of the tooth as a colored layer called plaque. Streptococcus bacteria inside the plaque then eat sugary food particles and excrete acid. This acid breaks down the enamel at the point where the plaque is present, creating the characteristic decayed hole in the tooth.
When babies are born, they do not have any bacteria living in the mouth. The first set of bacteria to colonize the baby typically comes from the mother, and the type of bacteria present also expands to include microbes specialized to living on teeth once baby teeth come in. After about three years of age, Streptococcus mutans bacteria have typically gained a foothold in the child's mouth, and for the rest of the person's life, these strains of bacteria live in the oral cavity. If oral hygiene is insufficient, these bacteria can produce decay.
Scientists, therefore, see tooth decay as a type of infectious disease. Infectious diseases like polio, flu and measles can all be prevented through vaccination, which involves taking one or more components of the causative microbe and presenting it to the immune system in a form like an injection. Once the immune system has recognized the microbe and produced a system to combat it, future infections can be immediately controlled. A caries vaccine uses the same system, and as Streptococcus mutans is the primary cause of dental decay, it is this group of bacteria that is under study.
Hypothetically, a caries vaccine could train the immune system into killing off Streptococcus mutans strains in the mouth. Decay could potentially be reduced and less children and adults would have to get fillings or more extensive dental procedures. Various forms of vaccination, such as oral vaccinations or products inhaled through the nose, could be used. Despite the potential benefits of a caries vaccine, however, several objections to its use have to be taken into account.
To be most effective, a caries vaccine would have to be given to children before Streptococcus mutans colonizes the mouth, which would be under about two years of age. The safety of vaccinating against the bacteria in young children is yet unknown, and scientists are also unsure as to whether Streptococcus mutans would be replaced by another bacterial species which could be more detrimental to oral health. As of early 2012, research is still ongoing into the potential of caries vaccines in various forms.