Microbiology dental caries
09 Aug 2017

Dental Microbiology

Microbiology dental caries

The basics of microbiology are important to fully understand the role of bacteria in oral health. It is these microbes which are either responsible or contribute to most oral health ailments. Whether it be the appearance of plaque on the teeth, gingivitis in the gums or dental cavities, bacteria directly attribute to all of these.

Bacteria are microscopic single celled organisms which can appear as either spherical, spiral or rod shaped. Whilst not all harmful, they are found everywhere, in fact there is expected to be about 5 quintillion (5,000,000,000,000,000,000,000,000,000,000) bacteria on the planet! The multiply rapidly by binary fission, meaning the cell will grow until it is big enough to split into two daughter cells. Each cell is identical to the parent cell. This does mean that it is hard for bacteria to survive when we attack them with antibiotics. However, random mutations can lead to a strain becoming resistant.

Streptococcus mutans is the main cause of dental decay or caries. The acid produced by certain bacteria causes decay to the tooth by solubilisation of the dental surface. These bacteria adhere to the surface in communities known as dental plaque.

The tooth surface normally loses some surface mineral from the action of the acid formed by plaque bacteria after ingestion of foods containing fermentable carbohydrates. This mineral is normally replenished by the saliva between meals. However, when fermentable foods are eaten frequently, the low pH in the plaque is sustained and a net loss of mineral from the tooth occurs. This low pH selects for aciduric organisms, such as S mutans and lactobacilli, which (especially S mutans) store polysaccharide and continue to secrete acid long after the food has been swallowed.

Fermentable carbohydrate foods which work with bacteria to begin the decay process and eventually lead to cavities include high sugar foods such as confectionary and soft drinks but also less obvious foods such as bananas, cereal and bread.

Prolonged films of bacteria on the teeth can also lead to gingivitis. This is an inflammation of the gums which if left untreated can result in loss of teeth. When the plaque is not adequately removed, it can cause an accumulation of tartar which is harder to remove and must be done professionally. The build-up of plaque and tartar irritates the gums causing them to retract, become inflamed and bleed. Luckily this is easily treated with improved oral hygiene and medicated mouthwashes.

The high presence of bacteria in a patient’s mouth leads to potential for transmission. This can be via aerated bacteria in blood or saliva or through poorly prepared equipment. Sterilisation of dental equipment is paramount to minimising the possibility of contamination in the practice. This will usually be the role of the dental nurse. There may be a nominated member of staff responsible for infection control and decontamination in the practice to ensure strict procedures are adhered to.

Instruments should be transported to the decontamination room as soon as possible to prevent any further transfer of bacteria. All utensils should then be carefully sterilised even if they were not used on the patient. There will be differing sterilisation techniques depending on the instrument and whether they are hollow, wrapped or include hand pieces.

With the risk of cross-contamination and disease, patients reserve the right to be treated in a clean environment with appropriately sterilised equipment. The careful handling of equipment to ensure this practice will be an important part of the dental nurse role.

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