Enamel..

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 Enamel

Enamel is the highest mineralized tissue of the body and totally acellular. Enamel is brittle and subject to fracture by trauma or heavy sharp-edge forces.

It is a semi-permeable membrane permeable to some fluids, bacteria, and their products. Enamel is the hardest substance of the body, it can withstand blunt, heavy masticatory forces. It has a


low tensile strength. 

Composition-

96%- Inorganic matrix.

4%- Organic matrix:-  1. 90% Amelogenins- rich in proline,                                                                histidine, glutamine & leucine.

                                                       2. 10% Non- amelogenins- Enamelin,                                                               tuftline, ameloblastin. 

Structure-

1. Rods- It is a long, thin structure extending from the Dentino enamel junction to the surface of the enamel.

2. Rod Sheaths- It is a thin layer seen peripheral to the rods. It also contains organic fibrils. entre of the rod is called Core of the rod.

3. Inter- Rod Structure- These are arranged circumferentially around the long axis of the tooth.

4. Hunter- Schreger Bands- These are alternating dark & light bands that are best visualized in the longitudinal ground section. The width of the strips is approx 50 microns. Runs parallel to Stria of Retizus.

5. Incremental lines of Retizus- Shows the rhythmic successive apposition of layers of enamel during the formation of the crown.

6. Neonatal Line or Ring- The line or boundary between the two portions of enamel i.e. postnatal & prenatal is called the neonatal lines.

7. Nasmyth's membrane- It is a non- mineralized membrane found between the gingival junction & enamel surface. 

8. Enamel Lamellae- These are very thin, leaf-like structures, sometimes visible to the naked eye. Contain mostly organic mineralized.

9. Enamel Tufts- These are hypocalcified enamel rods & interprismatic substance.

10. Dentino Enamel Junction- It is the scalloped interface between the enamel & dentine.

11. Enamel Spindles- They are mostly thickened at their ends they have been termed as enamel spindles.

12. Gnarled Enamel- In this enamel rods appear twisted, intertwisted, and intertwined or more irregular in the incisal & cuspal region.

13. Enamel pearl- This may appear as a globule of enamel.                            


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