Dental Disease -Tooth Decay

There are many conditions that affect the teeth. Here we will focus on the most common of dental diseases - dental caries, otherwise known as tooth decay. Dental caries is responsible for the vast majority of damage to teeth and still exists in parts of the world today in almost epidemic proportions. Which is a shame because it is completely preventable.

Anyone is a candidate for dental decay as long as there are teeth in the mouth and the mouth is exposed to those factors which break those teeth down.

Understanding how the tooth is built, and understanding what these pathological (destructive) factors are is critical in preventing dental decay. In fact this disease can even be reversed it if is caught early enough. And at the very least, catching it before it gets too advanced keeps it from destroying parts of your tooth further.

I know that the typical way to present this disease is by displaying pictures of blackened, rotting teeth. But it has never been my style to scare or intimidate my patients into health, but rather to educate them on how to take control of their own dental destiny. Early decay may not look as frightening as advanced decay, but it is just as dangerous and a lot easier to fix.


The Cause of Tooth Decay - It Is All About Acids

Not too long ago, dentists were taught that tooth decay followed a simple model. You have a tooth, you eat a lot of sugar,  you don't brush and floss well enough and the teeth rot away over time.  Then it was discovered that the bacteria that inhabit the mouth also play an important role in this disease. So the model was expanded to look like the diagram at the right.

If this model held true and you kept the bacteria off your teeth and limited your dietary sugar intake, then decay should not be possible, regardless of time. Or if you were not so good at diet and plaque control, but in time you intervened properly, you could at least stop the disease in its tracks

This model is mostly true but incomplete. Today we recognize that the central focus on why teeth decay is not just sugar or bacteria but the presence of acids on the tooth surface. The source of those acids could well be from the bacteria or the sugar, but it could also come from any other dietary acids, or foods that turn into acid in the mouth.

Regardless of that source, if the acids remain unchecked, teeth get softer and weaker. So now we focus on acids and the story has become a lot clearer.


The Importance of the pH of the Mouth 

We measure the levels of acids and bases in the environment using the pH scale. Anyone who owns a pool knows what pH is all about.  The pH scale measures from 0-14. Anything below 7.0 is considered acidic, anything above 7.0 is considered alkaline, or basic. a pH of 7.0 is neutral, neither acidic or basic.


It turns out that the minerals in your teeth are very sensitive to the pH of the mouth and for good reason. Oral acids are in abundant supply because digestion begins in the mouth. Acids and chemicals called enzymes break the food down the minute they pass into the oral cavity. The primary source of these chemicals are the resident bacterial population. Whether you are eating anything acidic or not, the mouth still has lots of acids in it, because the bacteria are there all the time.

So why isn't the mouth burning and feeling as if it is sore all the time? The answer lies in the constant presence of something else  in your mouth - the saliva.

It makes perfect sense that we would have evolved this way. Bacteria  are there all the time, they produce acids all the time, so saliva is also there all the time to neutralize those acids long after the food is swallowed. Because of your saliva, your mouth is a constant pH of 7.0, or neutral most of the time. But not all the time - depending on how much additional acids we throw into the mix and, even more importantly, how often these acids are being introduced.

For if the acidity of the mouth overpowers the ability of the saliva to keep it neutral, or if the salivary flow is not adequate enough, then bad things are going to happen, mostly to your teeth..

Once we recognized this effect of acids on the teeth and the important balance between bacterial acids and salivary buffers then the model for tooth decay had to be changed. Along with the addition of saliva and acids, other co-factors were also included in this new way that we look at dental decay.


A New Model for Tooth Decay 

Take a moment to look at the image below. It is the most up to date model to demonstrate the delicate balance between tooth decay and dental health.  It introduces some new terms such as demineralization, remineralization, and many others that we will shortly explain. The real thrust of this new paradigm is that it is not static, it moves left and right, up and down. In other words, you have some control as to where the scale sits when it comes to your mouth, if you know how it works.




Demineralization and Remineralization of the Tooth

If you read the section on "How Teeth are Built", you know that the tooth is predominantly made up of minerals that are  bound up in a crystal called Hydroxyapatite. Coincidentally, this mineral is mostly made up of the same minerals found in your saliva - calcium and phosphate ions. You will find out how important that is in a moment.

What we now know is that when the pH of the mouth dips below 5.5 (anything below 7.0 is considered acidic) the calcium and the phosphate ions begin to leak out of their crystals, weakening the tooth in the process. This process is appropriately called Demineralization.

What we also now know is that when the pH of the mouth returns back to a neutral 7.0, the calcium and the phosphate ions get sucked back up into the Hydroxyapatite crystals restoring the integrity of the tooth surface. This process is called Remineralization.  Because the saliva naturally contains these same two minerals, there is never a shortage of them to go back into the tooth. But it only happens if the pH rises back up to neutral, which takes about 30-45 minutes.

Because the pH of the mouth changes with whatever we eat, It is easy to imagine that the calcium and phosphate are in a constant flux back and forth, in and out of the tooth in response to the levels of acids and bases. Here is where you have tremendous control over which way the scale tips - toward repair and health or toward destruction and decay.

So lets first take a look at the dietary influences on acids and tooth decay


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