Tooth Development Flashcards
What are teeth composed of
Pulp, cementum, dentine, an amelodentine junction and enamel
Composition of enamel
96% mineral, 1-2% matrix and 2%water
Composition of dentine
70% mineral, 20% matrix and 10% water
Composition of cementum
65% mineral, 23% matrix and 12% water
Composition of bone
60% mineral, 25% matrix and 15% water
What does enamel cover
The anatomical crown
What is enamel produced from
Epithelium
Characteristics of enamel
96% inorganic, 2mm thick, translucent, non-vital, hard and brittle
What is dentine
Specialised connective tissue
Characteristics of dentine
Hard, strong, resilient, 70% mineral, 20% organic and contains collagen and dentine tubules
What is cementum
Mineralised connective tissue
What does cementum cover
The tooth root
What are the functions of cementum
Provides tooth support and is resistant to resorption
Interactions between epithelium gives rise to what
Enamel and the hyaline layer of the root
Interactions between the mesenchyme gives rise to
Dentine, pulp, cementum, peridontium-peridontal ligament and bone
When are the first signs of tooth development
Week 6
What are the stages of the tooth germ
Bud, cap, bell, late bell and crown
When does the bud stage occur
Week 8
What happens during the bud stage
A spherical epithelial condensation appears
Cell differentiation occurs
No histodifferentiation or morphogenesis
What happens during the cap stage
The cap shaped enamel organ
Cells are poorly histodifferentiated
Little morphogenesis
What happens in the late cap stage
An outer and inner layer of enamel epithelial forms
Some histodifferentiation and morphogenesis
What happens in the early bell stage
Enamel organ forms the inner enamel epithelium, the stratum intermedium, the stellate reticulum and the outer enamel epithelium
What does the inner enamel epithelium form
Amaloblasts
What do amaloblasts produce
Enamel
What does the ectomesenchyme form
Dental papilla and dental follicle
What does the dental papillae form
Odontoblasts
What do odontoblasts produce
Dentine and pulp
What does the dental follicle produce
Cementum, PDL and bone
What is cytodifferentiation
The process of the dental papilla forming odontoblasts
What is involved in matrix formation
Odontoblasts producing collagen rich predentine, the odontoblasts then retreat inwards and their long cell process form the dentinal tubule
What is mineralisation
Where predentine mineralises to form dentine
What is amelogenesis
Where the inner enamel epithelium forms ameoblasts
What do ameoblasts secrete
The enamel protien matrix
What does the enamel protein matrix undergo
Immediate mineralisation
Enamel with 30% mineral is known as
Immature enamel
What does immature enamel undergo
Gradual maturation
What happens in maturation of immature enamel
There is further mineralisation and the removal of most enamel proteins
What forms the root of the tooth
Cementum and dentine
What provides the signal for the development of the root
The root sheath
What is enamel made of
Tightly packed hydroxapatite crystals
What is the basic unit of enamel
Enamel prism
Shape of an enamel prism
Complex key hole
What is the prism core made of
Tightly packed hydroxapatite crystals
What is the prism sheath
A boundary composed of clearly differently orientated crystals
What is gnarled enamel
Where the prisms appear twisted around each other
Where is gnarled enamel found
At the cusps
What does gnarled enamel provide
Strength
What does growth of the enamel produce
Incremental growth lines - striae of Retzius
What do systematic disturbances cause within teeth
Accented lines
What happens when the striae reach the surface of the tooth
They create a furrow - perikynata
Orientation of the collagen fibres within dentine
Parallel to the dentioenamel junction
What do the collagen fibres provide
Strength
What is contained within the dentine tubules
Cell processes, nerves or fluid
What aspect of dentine is innervated
The inner aspect
When is primary dentine formed
During the tooth development up to the root completion
When is secondary dentine formed
After root completion
When is tertiary dentine formed
In response to pulpal insult
What happens to pulp volume with age
It decreases
What is the function of tertiary dentine
To prevent the stimulus reaching the pulp
How can fillings be kept in
Mechanically by undercut
Bound to the enamel by utilising the structure of enamel and acid etching
Bound to the dentine by acid demineralisation, infiltrating the collagen with resin and penetrating the tubules with renin
How is the majority of pulp innervated
Through non-myelinated axons
What are the two minor groups that innervated pulp
Alpha sigma myelinated fibres
Alpha beta myelinated fibres
What is the cell free zone
Plexus of Raschkow
What is around the odontoblasts
Marginal plexus
