The cementum is a part of the periodontium and it has fibers attached that help to connect the tooth to the alveolar bone. The cementum can be cellular and acellular.
This is a substance that covers the surface of dental roots. It is a part of the periodontal union and it provides a connection between every tooth and the surrounding alveolar bone. It is one of the main tooth substances aside from enamel, dentin, and dental pulp. It is also a very significant one. During life, as a person goes through aging stages, there are deposits of cementum mostly located on the tip of the tooth.
Cementum is a hard tissue. It is still a softer one compared to enamel and dentin. It is composed of minerals and an organic part. It covers the root of the tooth and also the dentin in the root. Cementum is made of 45% to 50% inorganic substances and 50% to 55% organic. The main inorganic substance is hydroxyapatite, that is also a part of the dentin and enamel. When it comes to the junction between cementum and enamel, there are three types of relationship. The first one is that there is a gap between the two substances. That happens in 5% to 10% of the teeth. In most cases, the cementum overlaps the enamel. And in 30% of the cases, they simply touch, without an overlap.
There are two types of cementum: cellular and acellular. As the name suggests, the first type involves cells in its structure, while the second one doesn’t. The two types of cells that are a part of the cementum are called cementoblasts and cementocytes. The first ones create new cementum. They produce this substance in layers and create a specific look. After they are finished with their main function, cementoblasts transform into cementocytes. They are located in small spaces called lacuna. They are connected with the surrounding tissue with small canals. Cementum doesn’t contain any nerves, but it is a vascularized tissue. The cellular cementum is more present in the apical part of the root, while the acellular is located near the crown.
The main function of the cementum is to connect the tooth to the alveolar bone. It is done through the periodontal ligament that is actually a complex union. It includes numerous flexible fibers that connect to different parts of the root. The endings of those fibers that are a part of the cementum are called Sharpey fibers. They attach the tooth to the alveolar bone and also allow its movements. Teeth don’t stay still in the socket. They have minimal movements that are controlled by the periodontal ligament. Roots move, turn are intruded and extruded. These are extremely small movements, but they still exist.
Another important thing to know is that cementoblasts create cementum throughout the whole life. So with age teeth lose some of the substance, especially the enamel on the surface. Because of that, a tooth can become shorter. That is when cementoblasts create more cementum in the apical part of the root.