Enamel Flashcards
describe features of enamel?
hardest tissue in body
resists abrasion
brittle
supported by dentine
covers tooth crown
translucent
transparency increases with mineralisation
what is abrasion of tooth?
based on physical contact
- physiological wear of tooth
what is attrition of tooth?
pathological wear of tooth
(grinding)
what supports enamel to make it less brittle?
dentine
will chip if unsupported
enamel varies in thickness. explain
thicker at inscisal edge
ocluso plate of molars is thicker than incised edge for function
describe the transparency and translucency of the tooth?
transparency = see through
translucency = light can pass through but not see through
where does the colour of teeth come from?
dentine
what happens when a tooth is developing?
starts soft and becomes hard while it takes shape (matrix formation)
what is the space between tooth and gum called?
vestibule
how are teeth formed?
buds positioned where they are going to erupt
how many deciduous teeth and how many permanent teeth?
20 and 32
2 features of deciduous
2 features of deciduous teeth.
already completely formed
no molars
when is crystallite orientation determined?
what is the orientation?
-during enamel formation
-some are parallel and some perpendicular to the enamel rod
how are crystallites in enamel positioned with the ameloblast membrane?
at right angles
what makes the template of crystallites?
ameloblasts
what tooth has wider roots? permanent or deciduous?
and why?
deciduous because permanent tooth is under it
where is the enamel more mineralised and harder in the tooth?
at the surface
- hardness decreases from cusp tip/ incised edge to cervical region
as tooth is in mouth for long period of time does it become more or less mineralised?
more mineralised
what is the enamel rod (prism)?
basic unit
where do rods run?
amelo-dentinal junction to surface
what do rods contain?
Hydroxyapatite crystals
how does the orientation of a rod vary?
within and along the rod
what is the content of enamel? (%weight and %volume)
Hydroxyapatite 95% and 90%
water 4% and 5-10%
organic matrix 1% and 1/2%
what does the organic matrix is enamel contain?
proteins, amelogenins
enamelling, peptides and amino acids
what does the organic matrix is enamel contain?
proteins, amelogenins
enamelling, peptides and amino acids
what is the shape of a HA crystal?
spiral
describe the enamel surface?
smooth
has pits and fissures
what is a fissure?
valley on the tooth
upper lateral
