Enamel Flashcards
What does cariogenic mean
Something that creates caries
What are the functions/structure of enamel
-Hardest tissue in body
-Resists abrasion
-Brittle
-Supported by dentine
-Covers tooth crown
-Varies in thickness
-Translucent
-Transparency increases with mineralisation
What is attrition
Attrition - the normal everyday wear of a tooth on incisal or occlusal surfaces
Erosion
what is abrasion
the wear of a tooth over unusual activity, more pathological wear of tooth. Usually associated with grinding teeth
Why must Enamel be supported
Never leave enamel unsupported as it will break much easier due to lack of dentine.
Amelodentinal junction ADJ/EDJ
Junction where enamel and dentine meet
Why does enamel have different thicknesses
-Surface enamel more mineralised and harder than deeper enamel
-Hardness decreases from cusp tip/ incisal edge to cervical region
-These properties have functional and clinical significance
Enamel on molars is thicker to withstand greater trauma due to chewing while incisors are primarily used for biting
Make up of enamel
Hydroxyapatite (HA)
-95% weight (90% volume)
Water
-4% weight (5-10% volume)
Organic matrix
-1% weight; (1-2% volume)
-Proteins: Amelogenins; enamelins, peptides, amino acids
What is erosion
The loss of tooth enamel caused by acid attack
What are the dimensions of an enamel rod
5 micrometres x 2.5 mm
How is rod structure determined (head + tail)
It is a result of variations in orientation of crystallites in different parts of the rod
What regulates the nanomechanical properties of enamel
Minor protein component (Amelogenins; enamelins, peptides, amino acids)
How are crytallites deposited
At right angles to ameloblast membrane
When is crystallite orientation determined
During enamel formatiomn
How does tooth whitening affect teeth (aside from whitening)
Removes organic content such as water and proteins which makes the enamel more brittle and at risk of fracture
What are hydroxyappatite crystallites composed of
Calcium
Phosphate
OH
Which material contains the largest HA crystallites
Enamel (greater than bon, cementum and dentine)
What can magnesium carbonate and flouride substitute within hydroxyappatite
Ca - Mg
P - CO3
OH - F
When is enamel more and less resistant to acid
High conc of CO3 in hydroxyappatite - Less resistant, more susceptible
High conc of Flouride in Hydroxyappatite - More resistant
How are enamel rods arranged
Run in a sinusodial course (parallel)
Where are Hunter-Schreger bands NOT present
Absent in outer enamel
What is Gnarled enamel
Present at cusps, optical effect of intertwined enamel
What causes neonatal lines (marks in enamel)
Trauma during intra-uterine life
What are enamel tufts
hypomineralised regions due to residual matrix protein at prism boundaries
What is enamel lamella
incomplete maturation of groups of prisms - ‘fault’ line extending through enamel thickness
Where are enamel lamella and enamel tufts found
Enamel -dentine junction
What are enamel spindles
Odontoblast processes extending into the enamel from the initial formation of the enamel
How to differentiate between enamel and dentine
scalloping on enamel edge
rods much thinner than dentine tubules
The scalloping found on the enamel-dentine junction (EDJ) is more pronounced in the incisal and cuspal regions, compared with the side of the crown what is the advantage of this
The scalloped junction may provide a better mechanical union between enamel and dentine. There is increased surface of contact. Also, the interlocking shape may provide more resistance to lateral, shearing forces.
What is the functional significance of gnarled enamel
The spatial arrangement of prisms may provide some resilience so that the enamel ‘gives’ very slightly during application of occlusal loads
What are enamel spindles
They are thought to be formed by odontoblast processes that extend for a short distance into the internal enamel epithelium layer of the enamel organ
What are enamel tufts
They represent regions of incompletely mineralised enamel matrix. They extend a short distance from the ADJ.
What are enamel lamellae
They represent regions of incompletely mineralised enamel matrix. They extend through the full thickness of enamel
What are dead tracts
These appear dark when viewed under transmitted light. The tubules are empty, and are sealed at the pulpal end by the deposition of tertiary dentine
