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48 terms

Enamel

STUDY
PLAY
Components of Enamel
1. Mineral Content (Hydroxyapatite) - 96% 2. Enamel Matrix 1% 3. Water 3%
Enamel structures
1. Prisms (Rods) 2. Sheath
Enamel Prisms (Rods)
Mineralized crystalline structure of enamel. Extends width of enamel from DEJ to outer surface. Perpendicular to DEJ. "Keyhole shape", largest mass
Enamel Sheath
Water and Matrix present. Formed by ameloblasts. Interprismatic or Interrod region covers rod/prism.
How many ameloblasts does it take to make a complete rod and sheath?
It takes 4 ameloblasts
How many cells does it take to make the head?
1 cell
How many cells does it take to make the tail?
3 cells
Ameloblasts must have
Tome's process present to lay down enamel and form prism
Amelogenins
Proteins found in developing enamel. Form bulk of matrix
Enamelins
Proteins found in mature enamel
Enamel development stages
1. Formative 2. Calcification 2. Maturation
Formative stage
There are two groups of matrix proteins (Amelogenins and Enamelins). Ameloblasts lay matrix but then break it down to allow room for hydroxyapatite
Calcification stage
Crystals are deposited
Maturation stage
Crystals enlarge (more amelogenins are removed to allow for growth of crystals)
Enamel Protective Stage
Enamel complete so enamel organ is now reduced enamel epithelium. Reduced enamel epithelium covers and protects new enamel prior to eruption. Ameloblasts secrete basal lamina to cover enamel (important in establishment of DGJ).
Newest enamel is located
Close to CEJ
Junctional epithelium is located
Directly above Connective Tissue
Sealants are placed on
Permanent teeth that have been in the oral cavity for about 1 year
Hunter-Schreger Bands
Taking enamel and cutting it cross-sectional and longitudinal and laying those 2 cuts next to each other. Band appearance
Gnarled Enamel
Enamel prisms that are twisted around each other at cusps or incisal edges.
Enamel Lamellae
Runs from DEJ to very outside. Fracture line. Only seen microscopically. Sensitivity because tubules are open to outer environment.
How many different ways may Lamellae form?
3 different ways
Enamel Tufts
Found from DEJ to inner 1/3 of enamel. May be calcified or not. Resembles bundles of grass. Bigger than spindles.
Enamel Spindles
Develop when odontoblastic processes are not withdrawn quickly. Tiny. Non-calcified enamel. Located next to DEJ.
Scalloped DEJ
Length of rods and tubules are irregular. Scalloped ridge increases adherence and strength. Prismless area.
Outer surface of enamel
Is prismless on a newly erupted tooth
Fluoride uptake requires
Hydroxyapatite
Enamel mineral content
96%
Dentin mineral content
70%
Bone and Cementum mineral content
40 - 45%
Which is a larger crystal, fluorapatite or hydroxyapatite?
Fluorapatite
Pre-Eruptive Calcification Stage
Fluoride is deposited during formation of Enamel crystals and incorporated as fluorapatite. Benefit from systemic fluoride.
Pre-Eruptive Maturation Stage
Fluoride Deposition continues after calcification. Benefit from systemic fluoride.
Post-Eruptive Stage
After eruption and throughout life of teeth. Topical uptake and rapid uptake during 1st years after eruption.
Types of developmental lines
1. Cross Striations 2. Incremental Lines 3. Lines of Retzius (Neonatal)
Cross Striations
Normal, growth lines
Incremental Lines
Same thing as imbrication lines or Perikymata
Lines of Retzius/Neonatal
Occurs if stress or trauma is experienced during birth
Incipient Carious Lesion
Has not completely broken through the enamel
Full blown Carious Lesion
Lost enamel structure and must restore tooth
Fluoride may be given
1. Systemically 2. Topically
Fluoride will not help the tooth
In Stage 1 of development, only during Stages 2 and 3
Fluoride uptake is more rapid on enamel
During the 1st years after eruption
Fluoride takes away
Hydroxy ion which was becoming demineralized and replaces it with the fluoride ion and you now have fluorapatite.
In the head, hydroxyapatite crystals run
Parallel to the Long Axis of the Rod
In the tail, hydroxyapatite crystals run
Perpendicular to the Long Axis
Zones of Enamel
1. Surface 2. Body 3. Dark 4. Translucent 5. Sound enamel
In the Surface, Body, Dark and Translucent zones
Hydroxyapatite is taken away, the crystals are larger and enamel is demineralized.