- Differentiation of ameloblast cells
Immediately after the first layer of dentine is formed, the inner enamel epithelium differentiates into ameloblast cells. The ameloblast cell is columnar in shape with its base attached to cells of the stratum intermedium; at the secretory end there is a pyramidal extension called the Tomes’ process (Fig)
- Secretion of enamel matrix
The enamel matrix is secreted through the Tomes’ process at the amelo-dentinal junction.
- Mineralisation of enamel
Calcium and phosphate ions are secreted into the enamel matrix and mineralisation occurs immediately; hydroxyapatite crystallites are formed. As ameloblasts move away from the amelo-dentinal junction, enamel prisms are formed. Prisms, also known as rods, run from the amelo-dentinal junction to the enamel surface; they contain millions of crystallites.
- Enamel maturation
During maturation from pre-enamel to mature enamel, the enamel crystallites increase in size and the organic content is reduced. On completion of enamel formation, the ameloblast cell loses the Tomes’ process, flattens and becomes the reduced enamel epithelium. The reduced enamel epithelium protects the enamel during eruption and will eventually become the junctional epithelium.