Pattern of mineralization in dentin

Dentin is first deposited as an unmineralized matrix which consist of mainly collagen type I and small amount of ground substance which is glycosaminoglycans. 

Mineraliztion of dentin starts after the deposition of mantle dentin ( first layer of dentin ).

On the basis of rate of dentin formation histologically dentin calcification occurs in two patterns which are:

1. Globular or (calcospheric) calcification 
2. Linear calcification

1. Globular calcifiication of dentin 

It involves the deposition of crystals in several discrete areas of matrix by heterogenous capture in collagen. With the growth of crystal globular masses are formed. These masses then fuses to form a single large calcified mass.

 This pattern is most commonly seen in circumpulpal dentin.

 2. Linear calcification of dentin

When rate of dentin deposition is slow the mineralization front appears more uniform and the process is said to be linear.

 This pattern is most commoly seen in mantle dentin.

For more click Pattern of mineralization in dentin