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Flashcards in Oral Biology Deck (80)
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what is the role of periodontium

retain tooth in socket, resist masticatory forces, provide a barrier for underlying tissue


what is the structure of cementum

similar to bone, lamellae arrangement but in a linear structure as opposed to radial like bone


what are the types of cementum and where can they be found

acellular extrinsic fibre cementum - found cervically, has no cementocytes so gets fibres from other sources - sharpey fibres
cellular intrinsic fibre cementum - found apically, contains cementocytes to produce it's own fibres, formed secondary


what is the structure of alveolar bone

outer layer of cortical bone - dense in lamellae arrangement, lamina dura - PDL attaches here
inner traberculae layer - woven bone with marrow, makes for a lighter structure and contains Volkmann's canals


what makes up the periodontal ligament

cells - fibroblasts, immune cells, cemetoblasts, cementoclasts, osteoblasts and osteoclasts
fibres - collagen type 1 and 3
ground substance - glycoproteins and proteoglycans
nerves and blood vessels


what structures give the PDL it's properties

strong and resist forces, load bearing - fibres
elastic - ground substance


what nerve fibres are present in PDL

Abeta - fast responding, for jaw jerk reflex
A delta - slower responding for changing mastication, also pain and temperature
C fibres - pain and temperature
autonomic - controlling blood flow


where can true periodontal fibres be found

connecting tooth to bone, cervically on cementum - sharpey's fibres. oblique, horizontal, alveolar crest


where can trans-septal fibres be found

connecting two teeth together - inter-dental


describe the change of PDL displacement when a load is applied

load applied e.g. mastication - initially rapid displacement of PDL, but as load persists, displacement is reduced
when load removed - initially rapid change back, but reduced as time goes on
adaptation due to visco-elastic properties


where does enamel and gingiva meet

junctional epithelium


what does bacteria attack in gingivitis/ perio

hemidesosomes at the basal lamina in junctional epithelium


where can crevicular epithelium be found

at the sulcus of the gingiva, before junctional epithelium


what is the mucogingival line

when the gingiva becomes attached to the mucosa, no longer free


what areas are para-keratinised

anterior dorsum of tongue, hard palate, attached gingiva, alveolar mucosa, vermilion of lip


what is the function of the pulp

provide nutrients to dentine, produce secondary and tertiary dentine, neuronal activation


what ways are pulp and dentine linked

developmental, functionally, structurally


how are pulp and dentine linked developmentally

both develop from dental papilla


how are pulp and dentine linked functionally

pulp stimulates secondary dentine production when sufficient primary dentine has been produced.
pulp stimulates tertiarty dentine production after tooth wear and dentine is exposed. exchange of materials between structures. pulp sends nutrients, nerves and dentine to dentine. chemicals and bacteria can travel from dentine to pulp


how are pulp and dentine linked structurally

the odontoblast layer separates the pulp and dentine. some nerves and immune cells (dendritic cells) can get through this layer to enter dental tubules


what types of dentine are produced in tertiary dentine

reactionary - produced by primary odontoblast when injury is mild
reparative - severe damage, primary odontoblasts are damaged, produced by secondary odontoblasts


how is dentinal fluid produced

blood vessels enter the pulp through apical foramen, leave in venules at a lower pressure, therefore fluid moves out of the capillaries and into the pulp chamber. as the pulp is enclosed, the fluid has nowhere to go so it travels through the dentinal tubules


how is the dentinal fluid described as protective

it has an outward pressure, prevents bacteria travelling inwards toward the pulp


what is rachow's plexus

nerve fibres as the branch out in the pulp chamber, sub-odontoblast layer


where are terminal nerve branches more commonly found in dentinal tubules

at cusps - 40%, cervical dentine has much less innervation


what is the hydrodynamic mechanism

when dentine is exposed due to tooth wear, the dentinal fluid can move around more freely. this activates nerve fibres, which reach AP and travel to the brain to stimulate perception of pain


what activates different nerve fibres

a delta - hydrodynamic mechanism
c fibres - direct activation via chemicals, electrical current or intense temperatures, more intense pain


how can different stimuli alter the hydrodynamic mechanism

different stimuli changes the direction of movement of dentinal fluid. when the fluid moves outwards - more likely to cause pain as nerve fibres are stretched more.
outward flow - cold, drying, decrease hydrostatic press
inward flow - heat, increase hydrostatic pressure


what controls blood flow to the pulp

autonomic neurones, metabolites, chemicals, drugs


how does inflammation occur in the pulp

exposing dentine, increasing dentinal fluid flow and activating nerve receptors, generates AP but also stimulates inflammation. kinins are produced - vasodilators which increase blood flow. in doing so - increases flow of dentinal fluid