DENTINOGENESIS

The process of synthesis, secretion, and matrix mineralization of dentin is called dentinogenesis.

Diffrentiation of Odontoblast

Under the influence of inner enamel epithelium, the ectomesenchymal cells of dental papilla differentiate to form odontoblast cells.

Inner enamel epithelium releases the following factors

• Transforming growth factor.

• Insulin growth factor.

• bone morphogenic protein.

These factors play an important role in the differentiation f odontoblast cells.

Fibronectin, decorin, laminin, and chondroitin sulfate are essential for differentiation of odontoblast cells. Differentiation first begins in the region of the future cusp.

• The cells of dental papilla immediately adjoining the acellular zone enlarge to form preodontoblast.

• Preodontoblast cells change shape from ovoid to columnar to become odontoblast cells.

• The nucleus is oriented towards the base.

• There is increased secretion of protein.

• Acellular zone becomes narrow and gets eliminated.

Matrix formation

Matrix formation begins with the appearance of large diameters collagen fibers called the vonkroff's fibers.

The vonkroff's fibers are laid down at right angles to the future cusp.

Odontoblast cells begin the secretion of matrix and move towards the pulp, several fibers join to form the process that embeds in the dentinal tubules.

As the matrix increases the odontoblastic process and the dentinal tubules increase in length.

The matrix of dentin is laid down at the rate of 4 um/day.

Mineralization

• Membrane-bound vesicles called matrix vesicles are involved in the mineralization of the dentin matrix.

• Vesicles contain enzymes called alkaline phosphate, alkaline phosphate increases the levels of phosphate in the matrix.

• Phosphate combines with calcium to form appetite crystals.

• Apettite crystals grown in size with the vesicle and rupture in the dentin matrix, they form bonds with adjacent crystals and matrix gets mineralized.

Deposition of dentin matrix is regulated by:

1. dentin phosphoprotein.

2. osteonectin.

3. osteopontin.

4. Gla - containing protein.

5. Chondroitin sulfates.