Dental caries or “decay”.


What's inside our mouths?



Except for newborns, our mouths are full of bacteria. Millions of bacteria are present in our mouths throughout life from shortly after birth. The way that our mouths are initially colonized with bacteria is an interesting story and can be found here.

These millions of individual bacteria are made up of hundreds of different types of bacteria. They live on our teeth, gums, tongue and all other surfaces in our mouths. While some bacteria are helpful, some can be harmful such as those that play a role in the tooth decay process. The bacterial colonies in our mouths form a bacterial community known as a “biofilm”.

Decay is a multifactorial disease and bacteria is just one part of the story…



Over time the western diet has continually evolved to the extent that today, the average Australian diet is very high in refined sugars. Those of you that have tried will know how hard it is to avoid sugar in today’s society! Even foods that claim to be sugar-free or low in sugar can have hidden amounts of sugar or sugar substitutes…

Sugar is another of the main factors that contributes to the decay process.


The Decay Process:

Any time we eat a meal or have a snack, most of the food we are eating will end up being swallowed and digested in our gastro-intestinal tract. A small portion of this food, indeed a microscopic amount, will remain in our mouths. This small amount of leftover sugars can get caught in the gaps in between our teeth, in the deep grooves and pits on the chewing surfaces or even rest on the smooth surfaces of our teeth.

When these sugars are left undisturbed in our mouths, the bacterial community in the plaque biofilm begins to slowly metabolise the leftover sugars. The result of this metabolisation is the production of acids. When these acids are released the pH inside your mouth begins to drop…


Once the pH in your mouth drops below the critical point of 5.5, your mouth is now in a state of demineralisation. This means that the mineral structures that make up your teeth begin to dissolve…

The use of fluoride has been shown conclusively to decrease the pH level required for demineralisation to occur (in this case a decrease is a good thing – use fluoride!) to a pH of 4.5. This is due to the replacement of the existing mineralised tooth structure with higher strength fluoride bonded minerals.

The initial stages of decay can be seen as “white spot lesions” which are an indication of demineralised tooth structure. If not caught and arrested at this stage through use of preventative treatments the decay process is likely to progress and cause more significant damage to your tooth structure. At the disease state progresses, you may require restorative treatment, endodontic treatment or perhaps even surgical treatment/removal of teeth or teeth structure. This is why regular check-ups and maintenance is vital!

It is important to note that the key factor in decay is the amount of time that your mouth remains in a demineralised state rather than the amount of sugar/acid. This means that constant snacking or grazing throughout the day will significantly increase your risk of decay. It also means that something as simple as a mouth rinse with water following any meal or snack will significantly help your dental health by flushing the oral cavity of most of the remaining sugars following eating. 


Remember, if you have any questions at all, please just ask!