Oral Biology Flashcards
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
what is the result of increasing flow of dentinal fluid in pulpitis
increase in flow - increase in nerve fibre activation. increased sensitisation. only requires small stimulus to stimulate AP - sensitive to cold air or to bite down
what can happen if inflammation and nerve activation is mild
can get regeneration of dentine
what are some variations of enamel thickness
thicker at cuspal regions, and incisal edges, thinner cervically
what is the main component of enamel
enamel rods - contain crystals of hydroxyapatite
what is the relationship of enamel rods to ADJ
perpendicular to ADJ
what other lines can be see in enamel
striae of retzius - incremental growth lines
describe the development of crystals in enamel
tomes process releases calcium phosphate encapsulated in protein capsule. this cocoon protein is broken down to allow calcium phosphate to become super saturated. crystal forms. as it is in the mouth, phosphate replaced with fluoride or hydroxyl
what is gnarled enamel
enamel with a higher concentration of rods - in cuspal and incisal regions
what are enamel tufts and lamellae
hypomineralised enamel. tufts project slightly, lamellae run the whole way
what are enamel spindles
odonotblasts that project on to enamel
what is hypersensitivity
when tooth wear results in exposed dentine which can cause nerve activation. results in short sharp pain in response to thermal stimuli, biting or touching
what are some causes of tooth wear
attritition, erosion, abrasion, periodontal disease resulting in gum recession
how do sensitive toothpastes work
contain potassium - moves membrane potential further from threshold - requires a stronger stimulus to generate nerve activation and pain perception
blocking tubules - contains novamin
how does novamin work
enters tubules, reacts with saliva to allow it to bind with collagen fibres to block tubules. release calcium phosphate - strong and acid resistant, layer over tubule. prevents stimulus entering tubule
what are the two types of bone and how do they differ
cortical - lamellae arranged in osteon, very dense, haversian canal through the middle
trabercluae - lamellae arranged in rods, with bone marrow between, much lighter
what is the difference between lamellae bone and woven bone
lamellae is laid down slower, has collagen in parallel arrangement and few osteocytes
woven is laid down rapidly in response to injury or in fetus, has many osteocytes, collagen in any direction
what are the different types of cartilage
elastic - external ear, epiglottis
fibrocartilage - pubic symphsis, vertebral discs
hyaline - end of growing bones, trachea, embryonic skeleton
what is the process of mineralisation of cartilage to bone
ossification
what are the two types of ossification and give examples
intramembranous - between bones in skull
endochondral - long bones
what are the stages of endochondral ossification
primary - as the embryonic skeleton is laid in hyaline cartilage, this is mineralised at diaphsial ossification centre
secondary - as the long bones continue growing, chondroblasts proliferate to produce cartilage, this is then mineralised at epiphyseal ossification centre
what is achondroplasia
genetic defect in which cartilage is not produced, lack of endochondral ossification. results in dwarfism with normal size skull as intramembranous ossification is fine
what is the resting membrane potential
-70 or -90, ICF negative to ECF due to arrangement of ions
what maintains the resting membrane potential
potassium ion channels constantly opening, continuous leak of potassium. active transport of Na/K pump - 3Na out, 2K in
describe the AP
ligand binds to receptor, generates opening of Na channels, as Na moves in, threshold of -55mV is reached, voltage gated Na channels activated, influx of Na. As voltage over shoots 0 and reaches +35mV, H gate closes, and voltage gated K channels are opened. Efflux of K causes membrane potential to return to normal. Refractory period of inactivation, before restored
what causes the refractory period
H gate of Na channel remains closed, despite the voltage returning, it is still unable to be activated as this gate is not voltage gated. As this gate opens, M gate closes ready for activation
describe the gates of the Na channel
2 gate - H and M. H is more commonly open, does not required to be activated. M gate requires a voltage to be opened. However, H gate becomes inactivated and closed at voltage above +35mV
what is saltatory conduction
direction of movement of AP, cannot go backwards due to refractory period. also, due to myelination, AP jumps from node to node of ranvier
what embryology does tooth structures develop from
ectoderm - enamel
ectomesenchymal (neural crest cells) - dentine, cementum, pulp
what are the stages of tooth development
initiation, bud stage, cap stage, early & late bell stage,
what happens at the initiation stage of tooth development
ectoderm, forming epithelium, invaginates into ectomesenchymal cells, forming dental lamina and vestibublar lamina
what happens at the bud stage of tooth development
EM cells become dense around dental lamina - form dental papilla. dental lamina also condenses to form enamel organ
what happens at the cap stage of tooth development
Enamel organ divides into 2 layers - internal and external enamel epithelium which meet at the cervical loop, dental lamina continues to develop
what happens at the early bell stage of tooth development
a further 2 layers of enamel organ develop. stellate reticulum - provides structure, support and nutrients to the enamel organ. stratum intermedium - between the IEE and EEE
what happens at the late bell stage of tooth development
the dental papilla differentiates into odontoblasts. this results in pre-dentine formation, as it is not mineralised, this stimulates IEE cells to differentiate into ameloblasts to begin enamel formation
describe dentinogenesis
dental papilla cells differentiate into odontoblasts, at each division, one odonotblast is produced and one cell remains EM. odonotoblasts allow for primary and secondary dentine formation. however, if injury results in damage to these odonotoblasts, EM cells remain to produce more and produce tertiary dentine.
describe the stages of amelogenesis
differentiation - odonotblast and dentine formation stimulate IEE cells to elongate and differentiate - columnar cells with nuclei at basal end
secretory - once differentiated, secrete organic proteins (amelogins) to produce the shape desired for enamel, only 30% mineralised at this point
maturation - once shape laid out, proteins are then broken down - matrix metallopeptidase - enamelysin - mineralisation of matrix
protective - ameloblasts regress, layer over top of enamel for protection
describe root formation
migration of cervical loop, IEE and EEE migrate (herte’s epithelial root sheath) , in doing so, stimulate dental papilla to produce odontoblasts, once reached length, epithelium regresses (may have some left over debris of malassez). dental follicle then contacts the root dentine - stimulates formation of cementoblasts to produce cementum
what causes amelogenesis imperfecta and how can it be seen
lack of protein matrix metallopeptidase due to genetic defect. means proteins cannot be removed and mineralisation cannot occur. lack of maturation.
mineral content of enamel and dentine is not different - no ADJ seen in radiograph. teeth will be more prone to tooth wear, yellow and rough surface
what is dentinogenesis imperfecta and how can it be seen
dentine is undermineralised. enamel relies on this for support so this is weakened. dentine moving more than it should - tooth wear. can be seen in radiograph - ADJ is apparent but cannot differentiate between dentine and pulp
what is the difference between gemination and fusion
gemination - one tooth (root) split into 2 crowns
fusion - 2 roots but crowns fused to 1
how does LA prevent sensation of pain
blocks Na channels, cannot reach threshold for AP, so not generated, no neuronal pathway to brain, no perception of pain
how does the structure of the nerve effect how the LA effects the nerve
LA has diffuse through connective tissue to reach nerve, will act on those closest to the membrane first. Also contains a lot of fat which will retain the LA for longer
what factors affect the sensitivity of a nerve to LA
diameter - wider diameter, more Na channels therefore more need to be blocked to prevent AP propagation. Larger axons will take longer to be anaesthetised.
Myelination - LA only has to work at nodes of ranvier, but there is a high concentration of channels here so high number must be blocked
what is the order in which nerves are blocked, from fastest to slowest
A delta, c, a beta, a alpha
what are the components of LA
aromatic ring - lipophilic for diffusion through membrane
amide or ester bond
amine with hydrochloride - hydrophilic, better water solubility
how does the amine group and hydrochloride work with LA
when together, ionised, active form but lipophobic so cannot cross membrane. must be in unionised, dis-associate inactive form to cross the cell membrane. once in, can ionise, re-associate and become active
give examples of an ester and amide bond
ester - benzocaine, topical
amide - lidocaine, prilocaine
why is a vasoconstrictor required in a local anaesthetic
LA is normally a vasodilator, increases blood flow so increases clearance and more is required. vasoconstrictor reduces the flow so it lasts for longer and less is required
what vasoconstrictors are used
adrenaline - used with lidocaine
felypressin - synthetic adrenaline, used with prilocaine
what is the difference between adrenaline and noradrenaline
adrenaline - systemically, no preference for alpha or beta receptors, so increases HR on beta 1 but also causes vasodilation on beta 2, no no overall increase in MAP
noradrenaline - higher affinity for alpha to beta, beta still increases HR but also causes vasoconstriction through alpha, increases MAP, causes the body to reduce BP to counteract this, might be light headed
