What do teeth have in common with ogres, onions, cakes, and parfaits? If you guessed layers, you’re right. (You’ve also probably seen “Shrek” a time or two.) Aside from ogres, all those layered things are pretty commonplace. In cakes, onions, and parfaits, the layers are all similar to one another, or they at least perform a similar function. They exist to be eaten.
As you probably expect, a tooth’s layers are much more complex. There’s a lot more to them than you’d suppose. Unsurprisingly, you’d probably never think about tooth structure during your daily oral hygiene routine.
For a tooth, each layer serves a different purpose. Let’s examine the surrounding structures first, then take a look at each tooth’s layers.
All your teeth attach to three important skull bones. The upper teeth have sockets in 2 paired maxillae that also shape portions of the nasal and facial structure. The lower teeth sit firmly inside the mandible, or jaw bone. These bones are not a layer of your teeth, but without them, your teeth would have no place to attach to your body.
Next, all those attachment points need a cushion. That cushion is your gums, a specialized membrane made mostly of skin-like cells and connective tissue. These gum-tissue cells also create the saliva that keeps your mouth from becoming dry. In turn, the saliva helps you begin the digestion process as you eat.
Inner Anatomy of a Tooth
A tooth’s root or roots consist of two layers. The outside layer is made of dentin. Dentin is living tissue that’s even harder than cementum. Dentin is one of the only parts of a tooth that grows. For instance, as a tooth matures, the dentin layer becomes thicker. It can also regenerate after infections, trauma, or dental treatments.
Inside the dentin rests a softer layer composed of pulp and other living tissues. The pulp has two main areas: the pulp chamber and at least one pulp canal. The pulp chamber rests inside the neck and crown of the tooth. Each pulp canal extends into a tooth root; that’s why sometimes they’re called root canals.
The pulp cavity is where the teeth’s nerve and blood vessels reside. Those vessels extend through the roots, through the cementum and gum tissue, and into the bones where they connect to the nervous and circulatory systems.
Enamel makes up your teeth’s outermost layer. It covers the exposed crown of each tooth as well as the area where a tooth’s neck meets the surrounding gum tissue. The strong cells and minerals in enamel make this the strongest substance in your body-it’s even stronger than iron or steel on the Mohs hardness scale.
Outer Anatomy of a Tooth
Now that we’ve discussed the innermost chambers of your teeth, it’s time to move outward, starting with cementum.
Cementum composes a thin but firm layer around a tooth’s roots, the portion that hides inside the gum tissue and bone socket. Cementum is actually stronger than bone. This connective tissue layer cements the teeth in place.
When you envision a typical tooth, you probably picture a ridged, rectangular head with two or three legs extending down on either side. Those legs are the tooth’s roots.
That said, not all teeth have multiple roots. In fact, most teeth in your mouth have a single root. Teeth with a single root include:
- Incisors, the four teeth at the front of your mouth
- Canines, the four teeth directly to the sides of the incisors
- Premolars, the eight teeth between your canines and molars
Between the root and the crown of a tooth you’ll find a small section called the neck. The neck acts like a dividing line between the major sections of a tooth’s exterior. Often the neck follows the gum line.
At the base of the neck below the gums, the hard enamel layer stops, so dentin and eventually cementum become the outside layer. (More on enamel and dentin in the next section.)
The crown is the part of each tooth that does all the work of chewing and biting. Normally, a crown is the only exposed surface of the tooth. That means your primary responsibility in caring for your teeth is to protect this outside layer from damage or decay.
Your dentist or your dental hygienist isn’t likely to quiz you about your tooth layers next time you go in for a cleaning. But, knowing about the different layers inside and outside your teeth helps you appreciate the complexity of your smile.
This information might also help you encourage you or your kids to practice good oral hygiene. To keep your teeth healthy from enamel to root, make sure to brush and floss every day and visit your dentist at least twice a year.