This post may contain affiliate links. You can read my full affiliate disclosure here.

Tooth Decay (Caries or Cavities or Fillings)

When it comes to looking and feeling your best, what’s the one thing you can do? Brush your teeth! Not only does brushing help keep your breath minty fresh, but it also helps prevent tooth decay. Tooth decay is caused by bacteria that feed on sugar in the mouth, forming an acid that breaks down the enamel of our teeth. If left untreated, it can lead to cavities and other forms of dental disease.

Let’s talk about the difference between a cavity and a filling and what tooth decay really is:

Cavities and tooth decay are the same thing. And they can also be known as dental caries. So a cavity, tooth decay, dental caries: all the same thing and may be used interchangeably at your dentist office. And what they really are are bacterial infections where the hard tooth surface starts to erode, creating holes in your tooth, literally a cavity in your tooth, a cavity decaying your tooth. This is caused by the acid byproducts of plaque, biofilm and the foods drinks that we consume. Some of the most common areas for this to happen, for cavities to develop, include the deep pits and grooves of your back teeth, your molars and between the teeth, where your toothbrush doesn’t clean, where you’re supposed to be flossing. And if you’re not a philosopher between the teeth is the most common area for bacteria to infect, thus the most common area for cavities.

Cavities Are Preventable

The good news is that cavities are preventable and diagnosing them early can prevent them from growing and spreading.

Protip: cavities are communicable diseases, meaning they can actually spread from one to another. They are contagious. So if you have one cavity between two of your teeth, it will often spread to the next tooth, to both teeth. So then you have two cavities.

Dental Fillings: What’s the difference?

Now, what is it filling? Lots of patients say to me they still don’t understand what a cavity is and then ask also what’s the difference between cavities and fillings? So we already answered what a cavity is. It’s literally the tooth getting eaten away by bacteria. But a filling is what happens after your dentist removes the tooth decay, removes the cavity and then fills it in to reinforce the tooth.

Today’s dental fillings are usually made out of tooth-colored material called composite or resin. They come in a variety of different shades of white so that your dentist can select the best color to blend in with your tooth to match your other teeth. Most offices do not use the amalgam silver fillings anymore. Some do, but it’s not as common. This is because the tooth-colored fillings bond closely to your enamel, making them less invasive than the silver fillings. There are, of course, always exceptions. For example, silver fillings may still be used if the cavity is super large or if the tooth is difficult to keep dry during the procedure. More common with kids in pediatric dentistry.

Now, if you have a cavity that has eaten through your enamel, the outer layer of your tooth and it has reached the next layer, the dentin layer of your tooth, a filling is always recommended to save your tooth from further damage. If you leave the decay there for too long without getting a filling, it will continue to eat away at your tooth, causing one of two things.


One, there might not be enough enamel left on your tooth anymore to properly fill it. If too much to surface has been eroded, a crown or a cap will usually be recommended to properly save your tooth.

Root Canal

If the cavity keeps getting deeper and deeper and reaches the nerve of your tooth, the innermost layer of your tooth. This is when you are most likely to start feeling pain and will need a root canal to properly finger tooth followed by a crown.


Cavities are the active tooth decay and the fillings are the healthy filled teeth which are no longer cavities. Cavities are preventable with good daily dental care and regular checkups at your dentist, I do have a posts all about how to prevent cavities and reduce your chance of tooth decay. So I hope that answers your question. You don’t want cavities, you don’t really want fillings, but you rather have a filling than a cavity because that means your cavity is no longer there and it’s filled up in nice and healthy.