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90 Cards in this Set
- Front
- Back
What are the three overlapping developmental phases in tooth formation |
-initiation -morphogenesis -histogenesis |
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What is initiation
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The development of the individual tooth along the dental lamina |
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What is morphogenesis
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the process that gives rise to the individual tooth shape
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What is histogenesis |
The differentiation of the cell to give either a mineralised or non mineralised tissue |
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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 |
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What is adult epithelium made from |
-superficial -intermediate -basal |
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What is the shape of the cells in the basal layer |
tall and columnar |
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What is the shape of the cells in the superficial layer |
long and flattened |
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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 |
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How is the dental lamina formed |
Basal cells replicate |
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What is the bud stage characterised by |
-spherical shape of epithelial condensation surrounded by mesenchyme |
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What is the cap stage characterised by |
-looks like a cap in cross section -early histodifferentiation visible (stellate reticulum, inner enamel and outer enamel) |
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What is stellate reticulum |
star shaped cells containing nutrients |
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What are the characteristics of bell stage
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-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 |
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Wher do the permanent teeth develop from? |
-molars from the dental lamina -other teeth from the successional lamina from their desiduous teeth |
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What will the dental papilla differentiate into |
the cells of the pulp and odontoblast layer to produce dentine and dental pulp |
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What will the dental sac differentiate into |
the cells of the cementum, periodontal ligament and alveolar bone |
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What is the cervical loop |
a loop where the outer enamel epithelium seperates from the dental sac (Will form hertwigs root sheath) |
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What is the late bell stage characterised by? |
-ameloblasts develop from the inner enamel cells which induces the production of an odontoblast layer |
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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 |
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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 |
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What are the cells in root formation |
-epithelial root sheath -dental papilla -dental follicle (dental sac) -odontoblast layer -epithelial restsof malassez -cementoblasts |
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What are ameloblasts |
cells that lay down enamel |
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What are odontoblasts |
cells that lay down dentine |
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What are cementoblasts |
cells that lay down cementum |
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What is the chemical composition of enamel |
96% HAP 3% water 1% organic material |
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What is the basic structure of a HAP crystal |
-hexagonal -width 60nm and 90nm -depth of 25nm and 30nm |
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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) |
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How is human enamel arranged |
Two groups of prisms running longitudinally and then a group running transversely with a key hole outline |
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What is type 1 prism arrangement |
prisms are circular/hexagonal with offset rows |
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What is type 3 prism arrangement |
modified form of type 1 with a prism in one row and interprismatic enamel in the row below |
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What does the amelo-dentinal junction consist of |
-tufts (transverse) -spindles (longitudinal and transverse) -lamellae (transverse) |
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What is the structure of the amelo-dentinal junction |
it is scalloped
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What is the path of prisms throughout the enamel |
-sinosodial path from the adj up to 2/3rds then parallel |
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What are hunter schregar bands |
-optical affects in the lower 2/3rds of enamel due to alternations in prism enamel |
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What is prismatic enamel |
the region directly under the surface |
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What is gnarled enamel |
Where prism arrangement was abnormal |
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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 |
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What is the chemical composition of dentin |
65% mineral 35% organic material(collagen) and water |
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How is mineral arranged in dentine |
HAP is arranged along collagen fibrils forming a meshwork |
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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 |
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How is dentine laid down |
4 micrometers per day in a diurinal rhythm |
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What are schregar lines |
compatability of primary curvatures |
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What are Von Ebner lines |
daily incremental lines
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What are contour lines of Owen |
compatability of secondary curvatures |
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What are anderson lines |
prominent lines superimposed onto von ebner lines |
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What is mantle and circumpulpal dentine |
-mantle is dentine directly underneath enamel -circumpulpal dentine is the rest |
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What is regular secondary dentine |
-dentine formed over the life of the tooth |
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What is primary dentine |
dentine laid down when the tooth is formed
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What is the boundary between primary and regular secondary dentine |
where the dental tubules change direction |
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What is intertubular dentine |
bulk material occupying space between the tubules which has a collagenous matrix in the form of meshwork |
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What is peritubular dentine |
hypermineralised, non-collagenous material around the odontoblast processes in the dentinal tubules |
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What is irregular secondary dentine |
When dentine is laid down at the pulpal surface of the dentine |
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What are the two subdivisions of irregular secondary |
-reactionary dentine (surviving odontoblasts) -reparative dentine (newley differentiated odontoblasts) |
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What are dead tracts |
regions of empty, black tubules |
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What are calcospherites |
isolated islands of mineral that are combined to mineralise dentine |
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What is the most common reason for dentine sensitivity |
hydrodynamics (fluid flow) produced by stimuli |
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What does the pulp contain |
-main arterioles and venules -nerve endings -connective tissue |
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What is Raschkows plexus |
small plexus of nerve endings below the cell-rich zone |
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What are denticles |
mineralised pulp stones |
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What is the periodontium made up from |
-lamina propia (non-calcified) -periodontal ligament (non-calcified) -cementum (calcified) -alveolar bone (calcified) |
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What is the arrangement of compact bone |
-parralel lamellae of bone -arranged in concentric circles around vascular canals |
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What is osteoid |
unmineralised pre-bone |
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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 |
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What are osteoblasts |
cells that lay down bone |
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What is bundle bone |
mature areas of bone with large sharpeys fibres |
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What are transalveolar fibres |
Intraboney fibres that cross the interdental bone and insert into the root of the adjacent tooth |
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What are the two types of incremental lines in bone |
-reversal line (Scalloped) -smooth regular line |
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How is the reversal line formed |
marks where resorption reversed to formation |
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How is the smooth regular line formed |
It is the former surface of bone deposition |
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What are osteoclasts |
cells that degrade bone |
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How do osteoclasts degrade bone |
-protons lower the pH and the brush dissolves the mineral -matrix is degraded by secreted enzymes |
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What are canaliculi |
small channels in the bone where osteoblasts and osteocytes can contact each other |
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What is an osteocyte |
an osteoblast that has become embedded within the matrix
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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 |
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What is the lamina propia |
-part of the gingivae that is dense and fibrous connective tissue |
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What seperates the enamel and the lamina propia |
junctional epithelium |
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What is the junctional epithelium made from |
non-keratinised, stratified, scaley epithelium which has a basal lamina on both surfaces |
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What is cementum |
calcified connective tissue which lies beneath enamel |
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What does cementum contain |
-cementocytes -cementoblasts -HAP -collagen fibres -water |
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What is the periodontal ligament |
soft connective tissue with cells and an extracellular metric comprised of fibrils of type 1 collagen |
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What are the cell rests of malassez |
small islands of epithelial cells that are the developmental processes of the tooth root |
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What are the fibres within the periodontal ligament |
-collagen -oxytalan |
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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 |
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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 |
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What are the vessels that carry blood vessels between intraboney spaces |
Volkmanns canals |
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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 |
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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 |
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What is the stress and strain of a tooth |
-strain is the increase in tissue lenght -stress is the load applied |
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Where is a load dissapated |
-oblique fibre system -fluid flow |