DEVELOPMENT OF CEMENTUM
DEFINITION & LOCATION
CEMENTUM (Substancia Ossea) - is a calcified mesodermal tissue forming the external covering of the anatomical roots of teeth.
It may also be defined as a modified bone covering the root, because it is similar to compact bone. The physicochemical properties, functions and structures of cementum are closely allied to bone.
FUNCTIONS:
1. It serves to attach the root of the tooth to the alveolar bone by means of fibers of periodontal ligament.
2. To compensate by its growth for the loss tooth substance due to occlusal wear.
3. It contributes to the continuous vertical eruption of teeth.
4. It regulates the periodontal space (as bone resorbs).
5. It protects the root dentin.
6. It repairs resorbed part of cementum surface, fractured roots and provides new surface for reattachment of broken periodontal fibers.
If the repair of the resorbed surface of the cementum reestablish the former outline of the root surface such is referred to as anatomic repair. If only thin layer of cementum is deposited on the surface of the resorption and the outline of the root is not reconstructed. It is referred to as functional repair.
In such case, the bone may project into the space.
PHYSICAL CHARACTERISTICS:
1. Cementum is light yellowish in color, lighter than dentin.
2. It is softer than enamel & dentin.
3. It lacks luster and has darker hue.
4. It is permeable.
CHEMICAL PROPERTIES:
• Cementum is composed of 45- 50% inorganic substance and 50-55% organic substance of water. The chief inorganic substance is hydroxyapatite. Of the inorganic substance, Ca, Mg, P are dominant. The inorganic elements found in enamel and dentin are also found in cementum. The chief organic substance is composed of collagen and mucopolyssacharide. The acellular cementum has higher inorganic substance and lower organic elements than cellular cementum. If cementum is decalcified it becomes soft because of lost of inorganic elements