Enamel And Dentine Flashcards
List 4 mineralised tissues
Alveolar bone
Cementum
Dentine
Enamel
List 4 non mineralised tissues
Oral mucosae
Dental pulp
Gingivae
Periodontal ligament
What forms the bulk of the tooth tissue
Dentine
What covers the crown of the dentine
Enamel
What covers the root of the dentine
Cementum
What is the appearance of dentine
Fine parallel tubules within a collagenous matrix for permeability
Rigid elastic tissue pale yellow
What is the unmineralised dentine pulp junction known as
Predentine
What creates dentine
Odontoblasts which then stimulate ameloblasts
Is dentine a vital tissue
Yes
What is the function of dentine
To act as a shock absorber dissipating large loads and force throughout the tooth structure highly elastic
How hard is dentine compared to other structures of the tooth
Harder than bone and cementum but softer than enamel
What is dentine composed of
70% inorganic mineral salts (hydroxyapatite crystals embedded in a collagen matrix)
20% organic substance (proteins)
10% water
List 6 non collagenous proteins in dentine
Dentine sialo phosphoproteins (DSPP)
Proteoglycans
Gla proteins
Acidic proteins
Growth factors
Lipids
What is the define between tubules called
Intertubular dentine
What shape does dentine follow
A curved sigmoid route known as primary curvatures (aka schreger lines)
What is the major feature of dentine
It’s dentinal tubules
What are lines of Owen
The small changes in direction in dentine known as secondary curvatures
When does secondary dentine appear
After completion of tooth formation increased crowding of odontoblasts
Where are dentinal tubules mostly formed
By the pulpal floor
Where do dentinal tubules mainly branch
At the periphery of the enamel dentine junction
What is translucent dentine
Forms with ageing due to tubule occlusion by deposits of peritubular dentine
Where is translucent dentine more pronounced
At the root apex
What are the 2 tertiary dentine synonyms
Reactionary dentine
Reparative dentine
What is tertiary dentine
Pulp induced to form calcified material in addition to 1st and 2nd dentine by a variety of external stimuli
What are the 5 external stimuli for tertiary dentine
Caries
Attrition
Cavity preparation
Microleakage around restorations
Trauma
What is reactionary dentine
Define formed in response to injury/insult made from existing odontoblasts
What is reparative dentine
Dentine formed in response to stimulus made from progenitor cells/newly formed odontoblasts
Where is peritubular dentine found
In wall of tubules highly calcified
Where is intertubular dentine found
Between tubules highly calcified
where is mantle dentine found
Outermost layer 1st dentine formed
Where is circumpulpal dentine found
Around the pulp uniform in structure except at the edges is the bulk of the dentine
What is primary dentine
Formed prior to apical completion formed more rapidly and more mineralised
What is secondary dentine
Formed after completion of root formation formed more slowly and is less mineralised than primary
Where is enamel thickest
At the cusps/incisal regions
What is special about the primary dentition of enamel
It is more opaque crystalline form therefore appears whiter
List 4 enamel functions
Mastication
Aesthetic
Protection
Dissipation of forces
How hard is enamel in knoop
296
How hard is dentine in knoop
64
What is enamels composition
96-97% mineral salts (hydroxyapatites, fluorides, carbohydrates)
3-4% organic substance (fibrillar matrix)
How is enamel structured
It is organised into rods (prisms) and interrods (interprismatic substance)
Where do ameloblasts come from
The inner enamel epithelium
What does amelogenesis do
Secrete matrix proteins that are responsible for creating and maintaining an extra cellular environment favourable to mineral deposition
What are the 3 main stages of amelogenesis
Presecretory stage
Secretory stage
Maturation stage
What does the first step of amelogenesis produce
A partially mineralised enamel 30%
what does the second step of amelogenesis involve
An influx of additional mineral content with the removal of material and water resulting in the 96% mineralisation
What are the 2 parts to maturation stage of enamel
Transitional phase
Maturation proper
What is maturation proper
The ABs become involved in the removal of water and organic material
What is the transitional phase
After the enamel has formed
ABs undergo significant morphological changes preparing for maturation
Reduction of AB height and a decrease in their volume and organelle content
What are the ABs in enamel
Referred to as post secretory cells although they still secrete other essential proteins
What is the maturative stage
Water and organic material is selectively removed from enamel with addition of inorganic material
What do ruffle ended ameloblasts do
Release of inorganic material
Proximal junctions are leaky and distal junctions are tight
What do smooth ended ameloblasts do
Remove proteins and water
Distal junctions are leaky while proximal junctions are tight
What is amelogenin
Accumulates during the secretory stage
What is enamalin
Crystal nucleation and growth
What is ameloblastin
Undergoes rapid degradation
Promotes mineral formation and crystal elongation
Highest concentration at enamel growth sites
Secreted together with amelogenins
What is the life of sulfated glycoproteins
Short half life in the enamel
Where is the tuftelin and what does it do
Localises at the DEJ and participates in its establishment
What pattern does enamel have
Striae of retzius
How does the pattern of enamel form
Because of a weekly rhythm of enamel production resulting in structural alterations of the rods
What type of striation does enamel have
Cross striations forming intervals across the rods
What is bands of hunter and schreger
Optical phenomenon produced by the changing orientations of adjacent groups of rods
What is gnarled enamel
Enamel tufts and lamellae
Perikymata aka imbrication lines
What contains the greatest concentration of enamel than the rest of the enamel
Gnarled enamel
Is projected from the DEJ for a short distance into the enamel
How is enamel formed
Secreted by ameloblasts via amelogenesis
