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What Happens In Your Mouth Every Time You Eat or Drink

Did you know that you are the life of the party?  Every time you eat fermentable carbohydrates, millions of bacteria in your mouth shout for joy as they snack on the food that you are eating.

Young Woman Eating PizzaThere’s just one small problem: after they’re done eating, they need to use the restroom.  Since there’s no toilet in your mouth, they just go on your teeth.  All of this acidic waste can start to dissolve your teeth.  Luckily, our saliva protects our teeth by gradually clearing out the acid and laying down new calcium to repair the patches of teeth that got dissolved.

The Stephan Curve: A Graphical View of What Happens In Your Mouth

It can be hard to visualize what exactly happens in your mouth every time you eat or drink.  To make it easier to visualize, the Stephan Curve was invented.

Below, you’ll find a Stephan Curve that shows what would happen in someone’s mouth who eats three meals a day and then a snack between lunch and dinner, and some cookies after dinner.

Stephan Curve

Before I talk about what this Stephen Curve is showing, here are some quick facts that will help you understand the above graph:

  • pH is a measure of how acidic something is.  The more acidic something is, the lower the pH, and the more harmful it is to our teeth.
  • The pH of our spit is usually right around 7.1.  This is slightly basic (as opposed to acidic.)  At this pH our teeth are safe, happy, and healthy.
  • When we eat carbohydrates or sugars, the plaque on our teeth munch on them as well and produce an acidic by-product.  This acid lowers the pH in our mouth.
  • If the pH drops below 5.5, our teeth start dissolving.

What Happened In the Above Stephen Curve

The Stephen Curve above shows a 24 hour period for someone who ate or drank five times:

  • 7 AM – Breakfast
  • 12 PM – Lunch
  • 2 PM – Soda Pop – Luckily it was just root beer.  Had it been a much more acidic soda, the line on the graph could have gone down to a pH below 3.
  • 6 PM – Dinner
  • 9 PM – Oreo cookies – This person started snacking on cookies at 9 PM.  Finally, at 9:30 PM, they stopped eating the cookies and gave their saliva a chance to rinse away all of the sugar and neutralize the acid in their mouth.

In total, this person allowed his teeth to dissolve for two hours during the day.  That still gave him 22 hours where his saliva could repair the damage that was done.  There thousands of things that could have happened to affect this Stephan curve.  What if, instead of eating ten Oreos from 9-9:30 had eaten one Oreo every hour from noon until 10 PM.  He would have created ten different episodes where his teeth were dissolving.  If he kept that up, he’d soon be visiting the dentist to take care of some cavities!

Your Stephan Curve Is Different

Your Stephan curve probably looks similar to the one above, but it is probably slightly different.  The way your Stephan curve looks depends on many factors such as:

1 – How often you eat during the day.  Each time you eat fermentable carbohydrates, your pH can drop into the area where teeth start dissolving.  If you eat enough times during the day, you’ll start to permanently destroy part of your tooth.  This is called a cavity.

2 – Type of foods you eat.  If you snack on foods that are healthy for your teeth, you are much less likely to dissolve your teeth by creating an acidic environment in your mouth.  For example, if you were to eat some cheese, the probably wouldn’t drop much below 7, giving your teeth something to smile about!  If you drink Coca-Cola, which is a very acidic drink, you will immediately drop the pH in your mouth and it will stay down there due to the sugar in Coke.

3 – Consistency of food.  If you drink some fruit punch, your saliva can quickly rinse the sugar away and return the pH of your mouth to normal.  However, if you eat Oreo cookies, it will take longer because the Oreos can get stuck up in the grooves on the chewing surface of your teeth.  As long as the Oreo stays stuck in your teeth, it will be feeding the bacteria and they’ll create acid that will dissolve your teeth.

4 – Your oral hygiene.  If you never brush, the bacteria can create a thick layer of plaque on your teeth.  Since it’s hard for your saliva to neutralize acid through a thick layer of plaque, you’ll spend a lot more time below a pH of 5.5 if you don’t brush your teeth everyday to remove the plaque.

5 – How much saliva you have.  If you don’t have much saliva, the sugar will stick around in your mouth longer because it won’t get rinsed away.  People with dry mouth get more cavities for this one reason.  If you find that your mouth is dry all of the time, here’s some things that may be causing your dry mouth.


Every time you eat something with fermentable carbohydrates, you feed the bacteria in your mouth.  This causes them to produce acid which dissolves your teeth.  Eventually, your body can restore order to your mouth by rinsing away the acid with saliva.  After the acid is rinsed away, your saliva repairs your teeth.  However, if you keep dropping the pH below 5.5, your saliva might not have enough time to repair your teeth and you could get a cavity.  The Stephan Curve is simply a graph that illustrates the pH in your mouth.

If you have any questions or comments, please leave them below in the comments.  Also, if you know anything about the history of the Stephan Curve or who Stephan is, let me know.  I have tried to learn about the history of the Stephan curve, but I remain clueless.  Thanks for reading!



  1. Tom, interesting article. Advice on avoiding decay usually states that the risk of caries is associated with the amount of sugar consumed. From what you write it seems that the frequency of sugar consumption is more important than the actual amount. I assume this from the graph you show. Is there any research which has shown how much sugar is needed to reduce the plaque pH to the point where it causes damage? For example, would just a small amount of sugar, say just 1g in a cup of coffee be a problem or does it take a significant amount like a whole teaspoon? I ask this because it seems to me that food which is so low in sugar that it wouldn’t even taste sweet may be almost as dangerous to a tooth as something clearly sweet tasting. If this were true then a lot of the advice on food packaging may be misleading.

    • The more acidic (so containing more sugar) the food is the longer it takes the mouth to get back up to a safe pH level. So both amount and frequency of consumption would contribute to this.

  2. This is great information. I have a class of grade 3 pupils and i want to discuss the effects of frequent intake of sugary food with them. How can i do it? Any vidoes?


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