enamel
TRANSCRIPT
![Page 1: Enamel](https://reader031.vdocuments.site/reader031/viewer/2022013115/55a4392c1a28ab4e5c8b4636/html5/thumbnails/1.jpg)
Enamel
![Page 2: Enamel](https://reader031.vdocuments.site/reader031/viewer/2022013115/55a4392c1a28ab4e5c8b4636/html5/thumbnails/2.jpg)
1-enamel is ectodermal in origins2-it is derived from inner enamel
epithelium of enamel organ.3-mature enamel is completely non cellular
Ameloblasts are derived from outer enamel epithelium)Mature enamel is completely acellular (True or false )
![Page 3: Enamel](https://reader031.vdocuments.site/reader031/viewer/2022013115/55a4392c1a28ab4e5c8b4636/html5/thumbnails/3.jpg)
1-Thickness2-Color3- Hardness4- Tensile strength5-Permeability6-Solubility
Physical characters
![Page 4: Enamel](https://reader031.vdocuments.site/reader031/viewer/2022013115/55a4392c1a28ab4e5c8b4636/html5/thumbnails/4.jpg)
thicknessIt is thick at the incisal edge and cusp tip of molars and premolars (2-2.5 mm) and ends cervically as knife edge
The thickest part of the enamel is present in---------, and………….
![Page 5: Enamel](https://reader031.vdocuments.site/reader031/viewer/2022013115/55a4392c1a28ab4e5c8b4636/html5/thumbnails/5.jpg)
colorThick enamel---------------------- bluish whiteDecrease in thickness-----------------------yellow due
to the underlying dentin
Healthy thick enamel is -------- in color, while thin enamel is …………in color
![Page 6: Enamel](https://reader031.vdocuments.site/reader031/viewer/2022013115/55a4392c1a28ab4e5c8b4636/html5/thumbnails/6.jpg)
hardnessEnamel is the hardest calcified tissue in the bodyBecause of its high content of minerals.Enamel can withstand load of mastication and resist wear process.
------- is the hardest calcified tissue in the body.Enamel is the hardest calcified tissue in the body (give a reason)
![Page 7: Enamel](https://reader031.vdocuments.site/reader031/viewer/2022013115/55a4392c1a28ab4e5c8b4636/html5/thumbnails/7.jpg)
Tensile strengthAlthough it is hard , enamel is extremely brittle and depends on the strength of the underlying dentin.
Tensile strength of enamel is greater than that of dentin ( true or false)
![Page 8: Enamel](https://reader031.vdocuments.site/reader031/viewer/2022013115/55a4392c1a28ab4e5c8b4636/html5/thumbnails/8.jpg)
permeabilityEnamel is selectively permeable, permitting partial or complete passage of ions due to the presence of microscopic pores.
Enamel is completely impermeable to ions(False or true)
![Page 9: Enamel](https://reader031.vdocuments.site/reader031/viewer/2022013115/55a4392c1a28ab4e5c8b4636/html5/thumbnails/9.jpg)
solubility
Enamel dissolves in acid media. Its surface is less soluble than deep enamel.
![Page 10: Enamel](https://reader031.vdocuments.site/reader031/viewer/2022013115/55a4392c1a28ab4e5c8b4636/html5/thumbnails/10.jpg)
Chemical composition
Mature enamel consists of:Mainly(96%)
inorganic substanceSmall (3%)
amount of organic substance
1%)&water
![Page 11: Enamel](https://reader031.vdocuments.site/reader031/viewer/2022013115/55a4392c1a28ab4e5c8b4636/html5/thumbnails/11.jpg)
Inorganic componentMainly calcium phosphate crystals
(hydroxyapatite crystals)
![Page 12: Enamel](https://reader031.vdocuments.site/reader031/viewer/2022013115/55a4392c1a28ab4e5c8b4636/html5/thumbnails/12.jpg)
organic componentMainly non collagenous proteins:
A- amelogeninsB- non-amelogenins
![Page 13: Enamel](https://reader031.vdocuments.site/reader031/viewer/2022013115/55a4392c1a28ab4e5c8b4636/html5/thumbnails/13.jpg)
Microscopic structure
1-Rods (prism).2- Rod sheath.3-Inter rodal cement substance
![Page 14: Enamel](https://reader031.vdocuments.site/reader031/viewer/2022013115/55a4392c1a28ab4e5c8b4636/html5/thumbnails/14.jpg)
Ground section Decalcified section
the organic substance is burnt and the inorganic substance remain
the inorganic substance is dissolved
and the organic substance remain
![Page 15: Enamel](https://reader031.vdocuments.site/reader031/viewer/2022013115/55a4392c1a28ab4e5c8b4636/html5/thumbnails/15.jpg)
Enamel rods1- Course.2- Number.3- Transverse striation. 4- Direction. 5- Gnarled enamel.
![Page 16: Enamel](https://reader031.vdocuments.site/reader031/viewer/2022013115/55a4392c1a28ab4e5c8b4636/html5/thumbnails/16.jpg)
the enamel rod starts straight : Courseat dentino-enamel junction (D.E.J.) for about 30 µ then has a wavy course till near the outer surface of enamel where it become straight once more.
![Page 17: Enamel](https://reader031.vdocuments.site/reader031/viewer/2022013115/55a4392c1a28ab4e5c8b4636/html5/thumbnails/17.jpg)
The number of the enamel rods varies from 5 millions in lower lateral incisor to 12 millions in the upper first perm.The number of the rods equals the number of the ameloblasts.anent molar.At the tooth surface there are about 20000-30000 enamel rods in 1 mm2
The density of the rods is at the DEJ about 10% higher than at the enamel surface.
The total number of enamel rods varies from------- to ---------
![Page 18: Enamel](https://reader031.vdocuments.site/reader031/viewer/2022013115/55a4392c1a28ab4e5c8b4636/html5/thumbnails/18.jpg)
transmission electron microscope
![Page 19: Enamel](https://reader031.vdocuments.site/reader031/viewer/2022013115/55a4392c1a28ab4e5c8b4636/html5/thumbnails/19.jpg)
![Page 20: Enamel](https://reader031.vdocuments.site/reader031/viewer/2022013115/55a4392c1a28ab4e5c8b4636/html5/thumbnails/20.jpg)
Scanning electron microscope
![Page 21: Enamel](https://reader031.vdocuments.site/reader031/viewer/2022013115/55a4392c1a28ab4e5c8b4636/html5/thumbnails/21.jpg)
Transverse striation of rods
![Page 22: Enamel](https://reader031.vdocuments.site/reader031/viewer/2022013115/55a4392c1a28ab4e5c8b4636/html5/thumbnails/22.jpg)
Deciduous toothpermanent tooth
Direction of rods
![Page 23: Enamel](https://reader031.vdocuments.site/reader031/viewer/2022013115/55a4392c1a28ab4e5c8b4636/html5/thumbnails/23.jpg)
Gnarled enamel
D
Twisted course of enamel rods
Gnarled enamel
Give short account on gnarled enamel
Gnarled enamel is twisted and intertwined rode structure associated with increase strength of the enamel ,Present mainly in the incisal edges and tip of the cusps. (enamel rods develop in planes of tension).
![Page 24: Enamel](https://reader031.vdocuments.site/reader031/viewer/2022013115/55a4392c1a28ab4e5c8b4636/html5/thumbnails/24.jpg)
Gnarled enamel
![Page 25: Enamel](https://reader031.vdocuments.site/reader031/viewer/2022013115/55a4392c1a28ab4e5c8b4636/html5/thumbnails/25.jpg)
Rod sheath
distinct thin layer peripheral to the rods L.M.Different refractive index, darker and more acid resistant, and less calcified and more organic.
-not distinct layer, but organically rich interE.M.rod space devoid of crystals.
![Page 26: Enamel](https://reader031.vdocuments.site/reader031/viewer/2022013115/55a4392c1a28ab4e5c8b4636/html5/thumbnails/26.jpg)
Inter rod substance
distinct cement substance with higher L.M.refractive index.
tail of the adjacent rod with different E.M.direction of the crystals
![Page 27: Enamel](https://reader031.vdocuments.site/reader031/viewer/2022013115/55a4392c1a28ab4e5c8b4636/html5/thumbnails/27.jpg)
INCREMENTAL LINES OFRETZIUS
![Page 28: Enamel](https://reader031.vdocuments.site/reader031/viewer/2022013115/55a4392c1a28ab4e5c8b4636/html5/thumbnails/28.jpg)
NEONATAL LINE
Neonatal line
Prenatal enamel
Postnatal enamel
![Page 29: Enamel](https://reader031.vdocuments.site/reader031/viewer/2022013115/55a4392c1a28ab4e5c8b4636/html5/thumbnails/29.jpg)
PERIKYMATAThe external manifestation of the incremental lines of Retzius represented as transverse wave like grooves on the surface of the enamel are known as
.perikymata
![Page 30: Enamel](https://reader031.vdocuments.site/reader031/viewer/2022013115/55a4392c1a28ab4e5c8b4636/html5/thumbnails/30.jpg)
HUNTER SCHREGER BANDS
•The dark bands (Diazones) absorb the light where the light bands (Parazones) reflect the light.
![Page 31: Enamel](https://reader031.vdocuments.site/reader031/viewer/2022013115/55a4392c1a28ab4e5c8b4636/html5/thumbnails/31.jpg)
ENAMEL TUFTAND ENAMEL LAMELLAE
![Page 32: Enamel](https://reader031.vdocuments.site/reader031/viewer/2022013115/55a4392c1a28ab4e5c8b4636/html5/thumbnails/32.jpg)
ENAMEL SPINDLE
It makes the area hypersensitive to pain
Enamel spindles are : A- odontoblastic processes cross the dentinoenamel junction.B- remnants of ameloblasts. C- enamel rods develop in planes of tension.
![Page 33: Enamel](https://reader031.vdocuments.site/reader031/viewer/2022013115/55a4392c1a28ab4e5c8b4636/html5/thumbnails/33.jpg)
Surface structure It is relatively structure-less layer covers the cervicalregion of the teeth. 30um in thickness in 70% of People, and it is hyper-mineralized.
![Page 34: Enamel](https://reader031.vdocuments.site/reader031/viewer/2022013115/55a4392c1a28ab4e5c8b4636/html5/thumbnails/34.jpg)
ENAMEL CUTICLE
It is delicate membrane coversthe crown of the newly Erupted tooth. It has the same Structure asbasement membrane
Primary cuticle secondary cuticle
It is non cellular keratinized layerformed by reduced enamel epithelium after tooth eruption,After removal of the primary oneby wear and brushing
![Page 35: Enamel](https://reader031.vdocuments.site/reader031/viewer/2022013115/55a4392c1a28ab4e5c8b4636/html5/thumbnails/35.jpg)
ENAMEL pellicleIt is a glycoprotein of saliva that covers the toothimmediately after eruption. It reforms within hoursafter removal.
ENAMEL plaqueWithin a day or two after the pellicle has formed it colonized With microorganisms to form bacterial Plaque.