Cementum facts for kids

Cementum is a special, hard layer that covers the outside of your tooth roots. It's not found on the part of the tooth you see, which is called the crown. Cementum helps your teeth stay firmly connected to your jawbones (the maxilla and mandible) by giving tiny fibers a place to attach. These fibers are part of your periodontal ligament.

What is Cementum Made Of?

Cementum is made from a mix of minerals and other materials. About half of it is a mineral called hydroxyapatite, which is also found in your bones and other parts of your teeth. The other half is mostly collagen, which is a type of protein, along with other natural materials.

• 45% to 50% hydroxyapatite (a mineral)
• 50% to 55% collagen (a protein) and other organic materials

How Cementum Develops

The process of making cementum is called cementogenesis. It's done by special cells known as cementoblasts. These cells are usually found on the surface of the cementum.

When a cementoblast gets surrounded by the cementum it creates, it changes and becomes a cementocyte.

There are also other cells called cementoclasts. These cells do the opposite job: they remove cementum instead of making it.

Where Enamel and Cementum Meet

The place where the tooth's enamel (the hard outer layer of the crown) and the cementum meet is called the cementoenamel junction. You might also hear it called the cervical line.

The way these two layers meet can be different for each tooth:

• Touching perfectly: Sometimes, the enamel and cementum meet exactly, like two pieces fitting together.
• With a small gap: In some cases, the enamel and cementum don't quite touch. This leaves a tiny gap that can expose the dentin underneath.
• Overlapping: Sometimes, the cementum slightly overlaps the enamel, covering a small part of it.

Different Kinds of Cementum

Cementum can be divided into two main types. These types are named based on where they are found on the tooth root and whether they contain cells.

• Acellular cementum: The word acellular means "without cells." This type of cementum does not have any cells inside it. It covers most of the tooth root's surface. Acellular cementum is very important for anchoring the tooth firmly to your jawbone. Because it doesn't have cells, it cannot make new cementum.
• Cellular cementum: Unlike acellular cementum, this type contains cells. It is usually found on the lower third of the tooth root. Since it has cells, cellular cementum can make more cementum and help repair any damage. Cellular cementum is a bit softer than acellular cementum.

See also

In Spanish: Cemento dental para niños