Dentin ^_^

DENTINDentin

Dentin is a crystalline material that enclose the pulp , formed by odontoblast and it is mesenchymal in origin.Dentin is coverd by enamel on the chrown and cementum on the root.

Dentin is the most voluminous mineralized conective tissue of the tooth.Forms the hard tissue portion of the dentino-pulp complex.

COMPOSITION

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.

PHYSICAL PROPERTIES

Vital and has nerve fibers but avascular.

Less dense than enamel on radiograph and appear radiolucent.

It is permeable.

Has elastic quality.

PHYSICAL PROPERTIES

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 TUBULEa. Odontoblastic cytoplasmic process.b. Dentinal fluid. c. Nerve fibers.

BASIC COMPONENTS

{

Dentinal tubules

Cross section

Longitudinal section

2. PERITUBULAR DENTIN

Immediately surround and forms the wall of detinaltubules

More highly calcified than intertubular dentin

3.INTERTUBULAR DENTIN

-Is the dentin found

between the peritubulardentin and it forms the most bulk of dentin.

BASIC COMPONENTS

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.

a. Mantle dentin.

b. Circumpulpal dentin

TYPES OF DENTIN

{Circumpulpal dentin

Irregular Secondary dentin

Secondary dentin

Predentin

Mentledentin

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 DENTINKnown as (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. Protection of the pulp.

2. Affects the color of enamel.

3. Shoch absorber and prevent fracture of enamel.

4. Determine the shap of the crown.

FUNCTIONS OF DENTIN

1. Imbrication line of Von Ebner,s

2. Counter line of Owen

3. DEJ

4.CEJ

5.Neonatal line

6.Tome,s granular layers

7.Interglobular dentin

8.Age changes

Microscopic feature Of Dentin

{

Lines of Owen Neonatal line

{

Incremental lines

{

Tomes granular layer

Tomes granular layer

Age changes

sclerotic dentin

Dead tract

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.

CLINICAL CONSIDERATION OF DENTIN

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.

.

CLINICAL CONSIDERATION OF

DENTIN