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All things about dental decay

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I’m sure many of us have been in a situation where you attend your regular check-up and clean and have your routine x-rays taken, then your dentist says “there appears to be a cavity on your upper left tooth that needs to be filled’. You may be frustrated by the news so in this blog post, we are going to break down the science of dental decay and all the nooks and crannies about it all so that this news becomes less frequently (and hopefully, one that you do not hear ever again)!

Firstly, how does dental decay occur? Most of you may know that sugar is the number one culprit for accelerating dental decay. This still holds true as it is the main contributor but in recent times, it is now understood that the cause of dental decay is multifactorial. Factors contributing include oral hygiene, fluoride, diet, saliva and plaque. We will briefly discuss how each of these factors are important.

Oral hygiene

This, as you may know, depends on the quality and quantity of brushing. You may recall with our hygiene appointments at True Smiles Dental that we ask a few questions about your cleaning habits around and in between the teeth. This helps us gauge the probability for both gum disease and dental decay to occur. In terms of quality, we use a special dye that helps disclose the soft plaque (a whitish film that overlays the tooth) around the teeth and gum line and indicates the duration it has been there.
Plaque is simply bacteria and for bacteria to grow, it requires food (it eats what you eat). When there are heaps of plaque (particularly the ones that are mature and are coloured dark blue/purple/light blue) sitting around the gum line and in between for too long, the plaque grows and starts to release toxins and enzymes that cause the teeth to weaken and break down. Hence, dental decay occurs. As such, this dye allows us to help you improve the quality of brushing. In terms of quantity, the magic number is twice daily brushing generally. There are other circumstances where an individual may need to brush more frequently but we will not dive into that topic today! As mentioned earlier about the growth of plaque, cleaning the teeth and gums frequently will limit the plaque from causing damage to the teeth and gums as much as possible. The typical brushing is best in AM and PM, but in some cases especially for individuals with differing lifestyles with work, it may differ. Provided a consistent twice-daily brushing is performed for two minutes, plaque levels will be kept at a minimum, thus reducing their contact time with your teeth and gums. Ultimately, a reduction in your risk of dental decay and gum disease.


Many toothpastes in the supermarket and drinking water around Sydney contain fluoride which all are topical (application on the teeth via direct contact) that has been shown to be the most beneficial way to re-strengthen the teeth. Similarly, to our bones, teeth are mainly composed of calcium minerals and hydroxyapatite (crystal-like lattice structure – think of a beehive) in which this matrix is quite strong. However, this structure does degrade from acid attacks and causes holes in the structure. As a result, dental decay starts to occur. This is where fluoride comes in to ‘remineralise’ (put back minerals back into the tooth). Now you’re probably thinking, why not add calcium back instead of fluoride? Yes, calcium is also another way to remineralise the tooth such as through dairy products and oral hygiene products such as Tooth Mousse. However, evidence shows that when fluoride remineralises the tooth, it forms a new crystal structure called “fluorapatite’ where the fluoride that replaces the calcium is more resistant to acid attacks and therefore, makes it LESS likely for the process of dental decay to progress. In summary, fluoride helps to protect and repair your teeth, making them stronger and more resistant to tooth decay. Of course, fluoride intake needs to be in moderation with respect to one’s age. An excess of fluoride can result in unfavourable effects to the teeth.


As mentioned earlier, sugar is the main culprit but is more complex than this. It is also about frequency, type of carbohydrates and when. Frequently look at how many times you are snacking – it is simply put, the more frequent snacking you are having the more likely you are feeding into the process of dental decay. This is because, through the frequent intake of food, particularly simple carbohydrates, the tooth is constantly being insulted and thus becomes weaker. The form of carbohydrate involves looking at how sticky it is. For example, a caramel toffee vs a marshmallow… the toffee will be much stickier than the marshmallow and therefore will be more prone to stick in the grooves of the teeth for prolonged time periods and at multiple occasions will lead to a very increased risk of dental decay. Not saying that a marshmallow won’t cause dental decay because it is at the end of the day, full of sugar. But snacks/foods that are stickier will likely speed up the process of forming a hole. Another important thing to note is hidden sugars… These include white bread and pasta, sauces/condiments, yoghurt, muesli bars and dried fruits. So be on alert when picking snacks for your children. Alternatives can include popcorn, rice wheels, crackers and cheese, and greek yoghurt. The type of carbohydrate also matters as well – simply put, is the food/snack mainly containing simple or complex carbohydrates? Generally, simple carbohydrates are in your lollies and confectionary and because they are in their simplest form, it is able to quickly act with the bacteria and cause acid to break down the tooth.


This looks at how much saliva is produced and the consistency. Saliva is important as it neutralises the acidity in the mouth, washes away some plaque and kills some of the bacteria (it has antibacterial properties).

Think of your tap in the sink and washing your dishes. If your tap is not running very well at a good rate due to a blockage, it will take a while for the soap to be cleaned off. Similarly, if there is a limited flow of saliva being produced, there is less capability of the saliva to wash the plaque and loose food away and the mouth is more acidic, leaving a drier mouth and thus, more likely for dental decay to form. Many medications and medical conditions can lead to dry mouth which we at True Smiles Dental check through your medical history to see if you’re susceptible to this and come up with some solutions to help reduce the risk for dental decay. Mouth breathing leads to a drier mouth too (read more about the implications of mouth breathing in the previous blog posts).


Plaque is the technical term for bacteria, but not only one single bacteria, but a colony. Think of an ant’s nest or a termite mound; plaque is a huge collection of bacteria stuck together by its own matrices. When it becomes a heap, you or your dental professional may mention a white/yellowish film that is sitting over the teeth and gum line. Depending on the bacteria, it may instigate gum disease and/or dental decay. There is several bacteria that cause dental decay, but the main culprit is Streptococcus mutans (S. Mutans). It is understood that some may have a higher bacterial load but many of the factors above can largely influence the bacterial activity and therefore, the risk for dental decay.

At True Smiles Dental Marrickville, we mentioned the special dye earlier that can help to assess how much plaque has colonised your teeth and even give you a time frame of how long it has been sitting on your teeth. With this, we can quickly stain your teeth and identify the various plaque that may be sitting on your teeth. With the aid of such tools, our patients can gain an in depth understanding of their mouth and what areas of their teeth that require further attention to ensure the happiest and healthiest smile possible. You’d be surprised how much colour there may or may not be on your teeth after trying it out!

All in all, I hope you have taken up a few new take new messages that may be helpful for you. As you can see, dental decay is more than just “stop eating lollies” and “cut down on the soft drink”, although those statements are true, we now see that there are other factors that contribute to dental decay. At your next appointment with True Smiles Dental Marrickville, ask one of our dental professionals to go through a risk assessment of all these factors with you if you are concerned about your decay rate and formulate an individualised advice for yourself to get you back on track. If you have any further questions, please contact our team on (02) 7228 7272 or book online at