Dentin 2

- Dentin is a crystalline material that enclose the pulp.- formed by odontoblast and it is mesenchymalin originated consists of tiny tubules or tubes.

- It is the second layer of the tooth and is normally coverd by enamel on the chrown and cementum on the root, making up the majority of the tooth's structure

Hard tissue forming the bulk of the tooth.

Softer than enamel but harder than bone and cementum.

It has a yellow color.

It has a rough surface texture than the enamel.

Vital and has nerve fibers but avascular.

Less dense than enamel on radiograph and appear radiolucent.

It is permeable.

Has elastic quality.

- Consists of 70% inorganic material mainly calcium hydroxyapitate crystals which appear plate like and smaller than that of enamel. - 20% organic matter mainly collagen.- 10% water.

Inorganic material 70%

Organic material 20%

Water 10%

1. DENTINAL TUBULES:

A long tubule extend from DEJ in the crown or DCJ in the root to outer wall of the pulp.

Follow a gentle ,S, -shaped curve in the tooth crown and are straight in the incisal edges, cusps and root areas.

COMPONENTS OF DENTINAL TUBULE:

a. Odontoblastic cytoplasmic process.

b. Dentinal fluid.

c. Nerve fibers.

2. PERITUBULAR DENTIN Immediately surround and forms the

wall of detinal tubules.

More highly calcified than intertubular dentin.

3.INTERTUBULAR DENTIN Is the dentin found between the

peritubular dentin and it forms the most bulk of dentin.

Support the enamel.

Protect the pulp.

Determines the shape of the crown.

Provide The Color of Tooth.

PRIMARY DENTIN:

Formed before root completion.

Formed by primary odontoblast.

Formed in faster rate.

Gives initial shape of the tooth.

It continues to grow till 3 years after tooth eruption.

It is more permeability.

Circumpulpal dentinMentle dentin

Large collagen fibers perpendicular First dentin formed against DEJ

Fine collagen fibers parallel to DEJLarge collagen fibers perpendicular To DEJ

Ground subestance from odontoblast only

Ground subestance from dentalPapilla and odontoblast

PRIMARY DENTIN

SECONDARY DENTIN:

(Regular secondary dentin)

Formed after completion of root formation.

Formed at a slower rate than primary dentin.

Thickness increase with advacing age.

Formed by primary odontoblast.

Less permeability.

TERTIARY DENTIN:(Irregular secondary or Reparative or sclerotic dentin) Frequently formed as a response to external stimuli such as

(dental caries, attrition). Formed only at the site of odontoblast activation. Formed by secondary odontoblast. Thickness increase with advacing age. The least permeability of dentin, therefore helping in

prevention of diffusion of noxious agent from the tubules.

1. As dentin is known to provide strength and rigidity to the tooth,care should be taken during tooth preparation.

2. Tooth preparation should be done under constant air water spray to avoid build up of heat formation.

3. Dentin should always be protected by liners,bases or dentin bonding agents.

4. Smear layer is formed as a result of tooth cutting(quantities of cutting debris) for bonding of restorative materials to tooth structue,this smear layer has to be removed by etching process.

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Mhammed Ali Al gnaidy (32) Mohammed Taleb Basarda (33) Shaikh Ahmed Bajaber (35)