Cementum is a calcified connective tissue that covers the anatomic roots of the teeth.
It is thinnest (20-50 um) at the cemento-enamel junction and gradually increases in thickness (150-200 um) toward the root tip where it surrounds the apical foramen.
Cementum is part of the periodontium which comprises the periodental ligament, alveolar bone, cementum, and gingiva.
Cementum shares some physical, chemical and structural characteristics with compact bone however it differs in the following characters:
• Cementum is avascular, having neither haversian canals
nor blood vessels and nerves in its matrix.
- It does not have the ability to remodel.
- It is highly resistant to resorption.
Physical characteristics :
- It is less hard than dentin.
It is Light yellow in color and lacks luster.
- It is semi-permeable. The cellular cementum is more permeable than the acellular.
Chemical composition :
Cementum contains 45-50% by weight inorganic substance and 50-55% by weight organic materials and water.
The inorganic portion consists mainly of calcium and phosphate in the form of hydroxyapatite plate like crystals. It contains also various trace elements. Cementum has the highest fluoride content of all the mineralized tissues.
The organic portion consists of collagen fibers mostly type 1 embedded in an amorphous ground substance of proteoglycans, glycoproteins and phosphoproteins.
|Cementum (%)||Bone(%)||Dentin (%)|
Comparison of chemical composition of the hard tissues