HISTOGENESIS OF DENTAL CEMENTUM
Root cementum is a hard non-vascularised and non-innervated tissues that covers the root of the tooth. Does not have ongoing remodelling like bone but continues to grow with age
- Origin: from the third element of dental germ, dental follicle after stimulation by Hertwig’s Epithelial Root Sheath formed by dental sac
Cementum Formation involves two tissues- Mesenchyme of the tooth follicle and the ectoderm of the Hertwig’s Root Sheath
Histogenesis of Cementum = Cementogenesis
Formation of cementum is called Cementogenesis and is due to cementoblasts and occurs right after the enamel has completely formed.
Hertwig’s Root Sheath
- The outer and inner enamel epithelia of enamel organ forms Hertwig’s Epithelial Root Sheath which is responsible for determining the shape of the root
- Two epithelial layers which are separated by stratum intermedium and stellate reticulum- which are connecting in the area of the future enamel cementum junctions (CEJ) and form the cervical loop
- There is a proliferation in depth to the dental follicle, as stratum intermedium and stellate reticulum are pushed out. This proliferation is called Hertwig’s Epithelial Root Sheath. It is located at the cervical loop of the enamel organ
- Function is to stimulate mesenchymal cells of dental follicle to differentiate
Three Layers of cells of Dental Follicle are formed:
- Innermost cells: differentiates to cementoblasts- build the cementum
- Middle Layer: differentiates into fibroblasts to build the PDL
- Outermost cells: differentiates to osteoblasts- build the alveolar bone
Stimulation of the Hertwig’s Root sheath initiates the formation of the root dentin by differentiation of odontoblasts from the dental papilla
- Both epithelial layers merged apically into one
- At its end are 4-5 cells without proliferation
- The do not divide by direct proliferation of the Hertwig’s Epithelial Root Sheath in order to control its length, thickness, curvature and number of roots
Cementoblasts deposit a thin acellular cementum over the root dentin called intermedium cementum. It plugs up dentinal tubules and isolates and protects the dentin.
- First layer of cementum serves as basis for building the cementum
induced by the proliferation of dental sac /dental follicle
Root sheath disintegrates but residual pieces that do not completely disappear are seen as epithelial cell rest of Malassez (ERM)
- Epithelial cells are grouped into clusters of 3-4 cells which are quickly removed from the root surface. It separates from the organic matrix secreted by cement regions