(2) Anatomy and Histology of the Periodontium - Enamel interactions (C) Flashcards
What is characteristic of the enamel-dentin junction?
Enamel-dentine junction has a scalloped pattern
What is shown in the histogram?
enamel dentin junction
Name structures A and B
A = enamel
B = dentin
Where would you find the scalloped interface of the EDJ?
Where shearing forces are high
beneath cusps and incisal edges
scalloped patterns increases strength
What direction would stria of Retzius run in this ground section?
left to right
(prisms run top to bottom)
What are enamel spindles?
Narrow, round tubules 8μm in diameter.
They extend up to 25um into the enamel.
Most commonly beneath cusps.
What is shown in this diagram?
enamel spindles
Where do enamel spindles commonly locate?
Most commonly beneath cusps.
How do enamel spindles arise?
pushing of the odontoblasts (cells that produce dentin) into newly formed enamel
these are remnants of the odontoblastic processes
How does the gnarled enamel form?
by the crowding of the ameloblasts
What is shown in this histogram?
enamel tufts
What is an enamel tuft?
Junctional structures in the inner third of enamel that resemble tufts of grass
What do tufts form in the same direction as?
They have the same direction as enamel prisms
What is the mineralised like of enamel tufts?
They are hypomineralised
What are tufts made from?
thought to be residual matrix protein at the prism boundaries.
What type of protein is a tuft?
minor non-amelogenin protein.
What is shown in this histogram?
lamellae
What is an enamel lamellae?
Structural faults that run through the entire thickness of the enamel.
Incomplete maturation of groups of prisms.
What can enamel lamellae be confused with?
Should not be confused with cracks produced during ground section preparation.
What type of mineralisation do enamel lamellae have?
Hypomineralised areas.
What are the enamel micro-porosities filled with?
Enamel pores are water filled spaces between the crystallites.
Enamel porosity makes 3-5% by volume.
Where are large enamel pores found?
Larger pores at prism boundaries.
What are the 3 arrangements between the cementum and enamel?
Pattern 1: the cementum overlaps the enamel (60%).
Pattern 2: the cementum and enamel meet at butt joint (30%).
Pattern 3: cementum and enamel fail to meet and the dentine between them is exposed (10%).
What always overlaps in the cement-enamel junctions?
the cementum always overlaps enamel as the enamel forms first
Name A-C and the black and orange arrows
Ground Section
A = Enamel
B= Dentine
C= Acellular cementum
Black arrows point to interglobular dentine
Orange arrows point to the granular layer of Tomes
What happens to translucency of enamel with age?
increases with age and staining = yellow
Does the composition of enamel change as we age?
The composition of surface enamel changes as a result of exchanges with the oral fluids.
Do caries increase or decrease as we get older?
There is a decrease in caries due to enhanced mineralisation
e.g. fluoride
