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90 Cards in this Set

  • Front
  • Back

What are the three overlapping developmental phases in tooth formation

-initiation


-morphogenesis


-histogenesis

What is initiation

The development of the individual tooth along the dental lamina

What is morphogenesis
the process that gives rise to the individual tooth shape

What is histogenesis

The differentiation of the cell to give either a mineralised or non mineralised tissue

What are the 7 tooth development stages

-epithelial band 6th week


-dental lamina 7th week


-bud stage


-cap stage


-bell stage


-hertwigs root formation


-alveolar bone and periodontal tissue formation

What is adult epithelium made from

-superficial


-intermediate


-basal

What is the shape of the cells in the basal layer

tall and columnar

What is the shape of the cells in the superficial layer

long and flattened

How is the primary epithelial band created

Superficial and basal cells multiply to increase the cell thickness. This happens alongside gene expression and cell signalling

How is the dental lamina formed

Basal cells replicate

What is the bud stage characterised by

-spherical shape of epithelial condensation surrounded by mesenchyme



What is the cap stage characterised by

-looks like a cap in cross section


-early histodifferentiation visible (stellate reticulum, inner enamel and outer enamel)

What is stellate reticulum

star shaped cells containing nutrients

What are the characteristics of bell stage

-morphodifferentiation and histodifferentiation are visible (Inner enamel cells are tall columnar)


-development of successional lamina


-dental papilla and dental sac form (formed of mesenchymal cells

Wher do the permanent teeth develop from?

-molars from the dental lamina


-other teeth from the successional lamina from their desiduous teeth



What will the dental papilla differentiate into

the cells of the pulp and odontoblast layer to produce dentine and dental pulp

What will the dental sac differentiate into

the cells of the cementum, periodontal ligament and alveolar bone

What is the cervical loop

a loop where the outer enamel epithelium seperates from the dental sac (Will form hertwigs root sheath)

What is the late bell stage characterised by?

-ameloblasts develop from the inner enamel cells which induces the production of an odontoblast layer

What is the process of amelogenesis

-IEE cells differentiate and elongate developing into columnar secretory cells


-differentiated ameloblasts secrete the initial matrix


-nucleus ascends and the cone shaped tomes process develops at the secretory end


-once full thicknes is reached the cell dies and forms a protective outer layer of the enamel

What is the process of dentinogenesis

-ameloblasts diffferentiate and elongate


-they stimulate the cell division in the dental papilla


-pre-odontoblast cells and daughter cells proliferate and develop into columnar secretory cells


-ameloblast degraes the basal lamina and allows signalling to odontoblasts so the dentine matrix is laid down

What are the cells in root formation

-epithelial root sheath


-dental papilla


-dental follicle (dental sac)


-odontoblast layer


-epithelial restsof malassez


-cementoblasts



What are ameloblasts

cells that lay down enamel

What are odontoblasts

cells that lay down dentine

What are cementoblasts

cells that lay down cementum

What is the chemical composition of enamel

96% HAP


3% water


1% organic material

What is the basic structure of a HAP crystal

-hexagonal


-width 60nm and 90nm


-depth of 25nm and 30nm

What is the arrangement of HAP crystals

-they are in prisms that run from the dentine to the tooth surface in changing orientations


-there is a cross-striation in the prisms every 6 microns which then have incremental lines superimpose (brown straie of Retzius)

How is human enamel arranged

Two groups of prisms running longitudinally and then a group running transversely with a key hole outline

What is type 1 prism arrangement

prisms are circular/hexagonal with offset rows

What is type 3 prism arrangement

modified form of type 1 with a prism in one row and interprismatic enamel in the row below

What does the amelo-dentinal junction consist of

-tufts (transverse)


-spindles (longitudinal and transverse)


-lamellae (transverse)

What is the structure of the amelo-dentinal junction

it is scalloped

What is the path of prisms throughout the enamel

-sinosodial path from the adj up to 2/3rds then parallel

What are hunter schregar bands

-optical affects in the lower 2/3rds of enamel due to alternations in prism enamel

What is prismatic enamel

the region directly under the surface

What is gnarled enamel

Where prism arrangement was abnormal

What is perikymata

a small depression running around the tooth which is produced when the incremental lines run obliquely across the prism and on the lateral surface of the crown

What is the chemical composition of dentin

65% mineral


35% organic material(collagen) and water

How is mineral arranged in dentine

HAP is arranged along collagen fibrils forming a meshwork

What is the basic structure of dentine

-dentinal tubules running from the outer dentine surface to the pulp containing fluid and the odontoblasts

-superimposed onto the primary curvature are more frequent, small wavelike deviations called the secondary curvature

How is dentine laid down

4 micrometers per day in a diurinal rhythm

What are schregar lines

compatability of primary curvatures

What are Von Ebner lines

daily incremental lines

What are contour lines of Owen

compatability of secondary curvatures

What are anderson lines

prominent lines superimposed onto von ebner lines

What is mantle and circumpulpal dentine

-mantle is dentine directly underneath enamel


-circumpulpal dentine is the rest

What is regular secondary dentine

-dentine formed over the life of the tooth

What is primary dentine

dentine laid down when the tooth is formed

What is the boundary between primary and regular secondary dentine

where the dental tubules change direction

What is intertubular dentine

bulk material occupying space between the tubules which has a collagenous matrix in the form of meshwork

What is peritubular dentine

hypermineralised, non-collagenous material around the odontoblast processes in the dentinal tubules

What is irregular secondary dentine

When dentine is laid down at the pulpal surface of the dentine

What are the two subdivisions of irregular secondary

-reactionary dentine (surviving odontoblasts)


-reparative dentine (newley differentiated odontoblasts)

What are dead tracts

regions of empty, black tubules

What are calcospherites

isolated islands of mineral that are combined to mineralise dentine

What is the most common reason for dentine sensitivity

hydrodynamics (fluid flow) produced by stimuli

What does the pulp contain

-main arterioles and venules


-nerve endings


-connective tissue

What is Raschkows plexus

small plexus of nerve endings below the cell-rich zone

What are denticles

mineralised pulp stones

What is the periodontium made up from

-lamina propia (non-calcified)


-periodontal ligament (non-calcified)


-cementum (calcified)


-alveolar bone (calcified)

What is the arrangement of compact bone

-parralel lamellae of bone


-arranged in concentric circles around vascular canals

What is osteoid

unmineralised pre-bone

What is at the junction between the periodontal ligament and bone

sharpeys fibres which insert into the bone with osteoblasts laying down new bone matrix

What are osteoblasts

cells that lay down bone

What is bundle bone

mature areas of bone with large sharpeys fibres

What are transalveolar fibres

Intraboney fibres that cross the interdental bone and insert into the root of the adjacent tooth

What are the two types of incremental lines in bone

-reversal line (Scalloped)


-smooth regular line

How is the reversal line formed

marks where resorption reversed to formation

How is the smooth regular line formed

It is the former surface of bone deposition

What are osteoclasts

cells that degrade bone

How do osteoclasts degrade bone

-protons lower the pH and the brush dissolves the mineral


-matrix is degraded by secreted enzymes

What are canaliculi

small channels in the bone where osteoblasts and osteocytes can contact each other

What is an osteocyte

an osteoblast that has become embedded within the matrix

In mammals what does the full socket and periodontium attachment facilitate

-shock absorber to protect brittle enamel


-allows the tooth to erupt out of its socket

What is the lamina propia

-part of the gingivae that is dense and fibrous connective tissue

What seperates the enamel and the lamina propia

junctional epithelium

What is the junctional epithelium made from

non-keratinised, stratified, scaley epithelium which has a basal lamina on both surfaces

What is cementum

calcified connective tissue which lies beneath enamel

What does cementum contain

-cementocytes


-cementoblasts


-HAP


-collagen fibres


-water

What is the periodontal ligament

soft connective tissue with cells and an extracellular metric comprised of fibrils of type 1 collagen

What are the cell rests of malassez

small islands of epithelial cells that are the developmental processes of the tooth root

What are the fibres within the periodontal ligament

-collagen


-oxytalan

What is the structure of collagen

triple helical torpocollagen molecule forms telopeptides


-these form a microfibril


-then a fibril with banding at 64nm


-arranged into bundles with ground substance in between

What is a typical fibroblast from a periodontal ligament like

-metabolically active


-metabolically coordinated


-contains intracellular vacuoles


-contains defence cells


-has a rich blood supply

What are the vessels that carry blood vessels between intraboney spaces

Volkmanns canals

What are the responsibilities of the periodontium

-resists forces on the tooth and displaces them


-mechanism that maintains the tooth in a functional position


-remodels adjacent bone and cementum


-provides a sensory input for jaw reflex activity

How does the ligament resist an applied load

-initial rapid intrusion phade


-it then maintains the intrusion at a slower rate


-if the load is then removed there is a rapid recovery and a slower extrusion

What is the stress and strain of a tooth

-strain is the increase in tissue lenght


-stress is the load applied

Where is a load dissapated

-oblique fibre system


-fluid flow