Dental Caries (decay)
 

What is the Stephan Curve?

The Stephan Curve is something we learnt about at dental school- it shows the effect of eating and drinking in your mouth clearly in a graphical form and is crucial in helping you understand dental decay.

It uses the pH scale; pH is simply a measure of how acidic an environment is .7 is the netural point, anything underneath that, is acidic and anything above it, is alkali (or basic) The further away from neutral you get the stronger the acid or alkali environment.

The critical pH level in your mouth is 5.5, as it is when the pH drops below this point, that your teeth start to demineralize or dissolve.

Stephan Curve
Stephan Curve


This is something you need to get to grips with, because it holds the keys to oral hygiene and not getting cavities. Suddenly everything the dentist has told you, will make sense from brushing and fluoride to diet advice. This will be one of those "Ah ha," moments- Read on!

Let's look at a healthy Stephan Curve.
healthy-stephan-curve.png
healthy-stephan-curve.png


This shows that someone ate 5 times:

Breakfast
Morning snack
Lunch
Afternoon snack
Dinner

Let's suppose that this person had 3 coffees with sugar during the day (or if you are not a coffee drinker let's pretend it's juice or soda) and picks at a packet of sweets over a movie in the evening- just before bed. We have marked this line in green- Can you see how the time spent with your teeth dissolving is greatly increased?

Example of an unhealthy Stephan curve
Example of an unhealthy Stephan curve


If this was your regular routine, over time you would find yourself with quite a few cavities.

Some interesting things to note. You can see:
  • Pretty much every time you eat something, the pH drops below the critical point of 5.5.
  • It takes 30-40 minutes for your saliva to get you back to the safe zone.
  • The longer you snack for, the longer you are at risk and the longer it takes for your mouth to recover.
  • If you have something else sugary to eat before your saliva has done its job- Boom! Your curve heads straight back down into acid territory a.k.a the danger zone and your teeth continue to demineralise.
Now we have seen what happens- how does this translate into practical terms?

Ok.Let's see how the diet advice from the dentist will correct the dangerous elements of the graph.
  • Avoid sugary snacks between meals- this is obvious. Eating more at meal times will help do this.
  • Group sugary things with your meals particularly sugary drinks- this is obvious
  • Limit chocolate, sweets etc. (not everyday) - this is obvious
  • Substitute sugar in coffee and tea with a non- sugar alternative/sweetner- this is obvious
  • Avoid sipping sugary drinks over many hours such as a bottle of coke - this is obvious
  • Drink water in between meals. - this is obvious.
  • (Gosh it all seems to make sense now doesn't it!)
  • Keep sugar clear of night time- nothing sugary before bed and nothing sugary during the night. At night your saliva flow rate drops- ever woken up with your tongue stuck to the side of your mouth and feel like you have been lost in the desert for a month- that's why. As we have seen, saliva is your natural protection so anything left in your mouth during this time does a lot more damage.

Ask yourself- What would your Stephan Curve look like?

Think about an average day...
  • What do you eat and drink?
  • When you eat and drink?
  • How much time does your mouth spend in the danger zone?
  • How much time does your mouth spend in the safe zone?

What affects the Stephan Curve?

  • How often you eat and drink. This is the most obvious aspect of the curve. The more separate occasions that you eat or drink, the more acid environments you create. Think of it that way- How long has it been since you last had something? (excluding our friend 'water').
  • How long you eat and drink for. Let's say you picked at lunch for over two hours instead of sitting down andeating in a single sitting of 20 minutes, your time spent in the danger zone is increased 6 fold.
  • What you eat and drink. Healthy foods and snacks will contain much less fermentable carbohydrate or sugars; less for the bacteria to feed on. As such, the amount of acid produced is less and you return to a neutral state much more quickly. Compare the effect of eating some cheese - a very neutral food (good for your teeth but not for your arteries, against something sugary like chocolate .
  • The consistency of the food. It has been shown that it is much more difficult to clear sticky foods from in and around your teeth. The obvious example is toffees which take some serious chewing and get wedged in the patterns on the tops of your teeth for sometime afterwards. Saliva can't wash this away, in the same way it could. for example, a glass of lemonade, While it remains, it provides sustenance for the bacterial plaque; prolonging the release of acid onto your teeth.
  • What you eat or drink after the sugar intake. If you have a glass of water straight afterwards or chew sugar free gum or cheese, these will all help to neutralize the acid and speed up the time it takes to get back to the safe zone.
  • The amount and quality of your saliva. This is our 'knight in shining armour' in the fight against tooth decay. Without it, you would get a condition known as 'xerostomia' or dry mouth; the acid is not washed away and neutralized, so instead of it taking 30-40 minutes to recover, it can take well over an hour. Your teeth are deminerising for longer and the risk of getting cavities much greater. There are ways to help with dry mouth if you suffer from this condition.
  • The amount of bacteria (plaque). If you keep your mouth nice and clean then there is less bacteria around to feed on the sugars in the food and on the drinks you consume. This means less acid will be produced and so your saliva will remineralise your teeth that much quicker. What you eat actually goes one step further and determines the type of bacteria in your mouth. If you consume a lot of sugar, you will find you have much more damaging bacteria than someone who doesn't- their plaque would contain bacteria which is less efficient at producing acid and so less damage is done (if and when, they 'do' consume some sugar). Frequently eating sugar makes your mouth into a farm for breeding the 'more evil bacteria'; in particular 'streptococcus mutans'.
  • Fluoride. Fluoride stops demineralization, promotes remineralisation and reduces the amount of acid plaque produces. Thus it helps speed the recovery into neutral territory after an acid attack.