Enamel Flashcards
What is enamel made of
Hydroxyapatite crystals 95%
Water 4%
Proteins 1%
Shape of enamel prism?
Keyhole shaped
Physical characteristics of enamel
- thickest at the incisal edge and thinnest at the cervical margin
-hardest tissue in the body , resists abrasion - brittle
- Highly mineralised
- cannot be repaired or replaced
Surface enamel vs subsurface enamel
Surface enamel is thicker, less porous and harder, denser
Surface enamel contains more fluoride ions but less magnitude/ carbonate ions
Why does translucency of enamel increase with age?
Less internal reflection, dentine shows through, demineralisation
Principal mineral component of enamel ?
Calcium hydroxyapatite
What is the cell that forms organic template of enamel?
Ameloblast
Basic structural unit of enamel
Enamel prism or rod
What is the difference between attrition and abrasion?
Attrition is tooth loss involving tooth to tooth contact eg. Bruxism
Abrasion is tooth loss involving friction between tooth and outside material eg. Over brushing or use of abrasive toothpaste
Differences between dentine and enamel crystals
Dentine crystals are smaller
Scallop structure at the dentine-enamel junction
Why does fluoride help
Fluoride ions replace OH ions to form fluroroapatite which is more stable than hydroxyapatite
Why is enamel able to withstand the shearing forces even though it is brittle?
It is supported by dentine. Never leave enamel unsupported after any procedure, consultant will fail you
Where are teeth formed from?
Tooth bud
What does ameloblasts secrete
-secrete an organic matrix comprised primarily of several enamel proteins including amelogenin (90%) ameloblastin (5%) and enamelin. This matrix then undergoes mineralisation
Some histological slides do not have enamel shown, why?
Enamel is mainly composed of mineral, ie hydroxyapatite. Some slides are Demineralised specimens so the entire enamel is not shown on the slide.
How to differentiate between dentine and enamel on a slide?
- Striae of retzius (oblique striations in enamel)
- Cross striations (little lines in each enamel rod)
- Pointy bit of the scallop faces enamel
- Space between dentinal tubules are larger than spacing between enamel rods at ADJ
Is enamel brown?
No, enamel is translucent. It appears brown on the slide because of the light and sectioning
Abfraction
When the ADJ fractures and the enamel pops out
What is the characteristic of enamel at the fissures
It is thinner, the enamel rods
What are ground sections
Hard Mineralised tissues remain intact
How does enamel differ from all other calcified tissues in the body
It does not have cells within it or on its surface
Where is enamel the thinnest?
Cervical margin. Rmb that there is no enamel at the apex
Does the mineral content increase or decrease from the ADJ to the surface
Increases
What are so common ions that are present in enamel
Fluoride magnesium carbonate
Two main types of incremental lines in enamel
Cross striations and Striae of Retzius
Dentine is more vulnerable at this site.
Enamel is thinner at the fissure so caries more likely at fissures
Enamel rod direction
The rod direction in the crown is normally perpendicular to the incisal surface
Four enamel proteins
Amelogenins, ameloblastins,enamelins, tuftelins
Does enamel contain collagen
No
Tomes processes
Right angle deposition ?
