CTB theme 2 Flashcards
What are the 3 phases of tooth development ?
initiation
morphogenesis
histogenesis
What is initiation ?
appearance of tooth germs
this stage determines the tooth position
What is morphogenesis ?
cell proliferation and movement
determines the tooth shape and type
What is histogenesis ?
cell differentation and specialisation
leads to the formation of dental tissues
What are the 3 stages in the initiation phase of tooth development ?
formation of the priamary epithelial band
condensation of mesenchymal cells
formation of the dental and vestibular lamina
What happens during the formation of the primary epithelial band ?
6 weeks in utero
a continuous band of odontogenic epithelium forms around the mouth in the upper and lower jaws
each band corresponds with the dental arches
Why does the primary epithelial band form ?
as a result of a change in the cleavage plane of dividing cells
What happens when mesenchymal cells condense ?
epithelial band grows into ectomesenchyme
What is ectomesenchyme ?
neural crest derived mesenchyme
What happens in the formation of the dental and vestibular lamina ?
7 weeks in utero
primary epithelial band divides into the dental and vestibular lamina which grow into the ectomesenchyme
What eventually happens to the dental lamina ?
it continues to proliferate lingually leading to the development of 20 epithelial outgrowths - tooth germs
How is the vestibule formed ?
epithelial cells proliferate and the central cells enlarge and degenerate to produce the vestibule
What are the stages of the morphogenesis phase ?
formation of a tooth bud
early cap stage
late cap stage
early bell stage
What happens in the formation of a tooth bud ?
elongation of the dental lamina leads to localised swellings- proliferates rapidly
ecomesenchymal cells condense
What happens at the early cap stage ?
11 weeks
epithelial outgrowth resembles a cap which sits on condensed ectomesenchyme
What is the condensed ectomesenchyme called ?
the enamel organ
it will eventually form the enamel of the tooth
What happens in the late cap stage ?
a group of non dividing cells form the enamel knot
the condensed ectomsenchyme cells under the enamel organ from the dental papilla
the condensed ectomesenchyme surrounding the enamel organ forms the dental follicle
What is the enamel knot ?
a transient molecular signalling centre
What does the dental papilla form ?
the dentine and pulp
What does the dental follicle form ?
periodontal tissues
What happens in the early bell stage ?
cells on the periphery of the enamel organ become cuboidal and form the outer enamel epithelium
cells bordering the dental papilla have a columnar shape - inner epithelium
What is in the middle of the enamel organ?
stellae reticulum
What is the stellae reticulum characterised by ?
star shaped cells
cells are connected by desmosomes
intracellular spaces filled with GAGs
What do GAGs act as ?
shock absorbers
What is the stellae intermedium ?
in the bell stage some epithelial cells between stellae reticulum and the IEE diffferentiate into the stellae intermedium
What are characteristics of stellae intermedium ?
2-3 cell layers thick
high activity of alkaline phosphatase
involved in protein synthesis and substance transport to and from the IEE
supports ameloblasts.
What is the role of the dental papilla ?
generates fibroblasts and ectomesencymal stem cells of the pulp
produce odontoblasts
What is the role of the dental follicle ?
support the enamel organ with nutrients
supports the generation of tooth forming tissues
What is the inner layer of the dental follicle like ?
condensed and vascularised and in contact with the OEE
What is the outer layer of the dental follicle like ?
loose and vascularised and contacts the developing alveoalr bone
What are the stages of the tooth histogenesis phase ?
late bell stage
reciprocal tissue interactions in crown formation
protection of the crown after completion
What happens in the late bell stage ?
odontoblasts and amelobalsts secrete predentine and preenamel
stellae reticulum moves downwards
breakdown of the dental lamina
enamel organ looses contact with the oral epithelium
Why does the stellae reticulum move downwards ?
protect the cellular area of the tooth
What is the cervical loop ?
growing end of the enamel organ
located where the IEE and OEE meet
involved in root formation
What does stratum intemedium do in the late bell stage ?
produces alkaline phosphatase which leads to enamel mineralisation
What does stellae reticulum do ?
protects and maintains tooth shape
What does the OEE do ?
maintains tooth shape and exchanges substances with the dental follicle
What are odontoblasts ?
dental papilla cells
What are ameloblasts ?
IEE cells
How is the IEE separated from the dental papilla ?
cell free zone
What happens when the IEE cells elongate ?
they become preameloblasts which secrete signalling molecules that induce odontoblast differentiation of dental papilla cells
What happens once the odontoblasts start secreting predentine ?
they align and release signals that induce differentiation of preameloblasts into ameloblasts- produce pre enamel
When is the protective epithelium for the crown formed ?
when the crown is formed
How is the REE formed ?
flattened ameloblasts and remnants of the enamel organ
What is the purpose of the REE ?
it covers the crown and stops enamel of the erupting tooth being attacked by osteoclasts in resorption
Which teeth need successive tooth germs ?
incisors, canines and premolars
How are successional tooth germs formed ?
they bud off lingually from the dental lamina at 5 months in utero
What do successional tooth germs do ?
they remain dormant until their development is initiated
How does molar development occur ?
dental lamina grows posteriorly
backward extension gives rise to epithelial outgrowths that form molar tooth germs
What are ectodermal appendages ?
epithelium and mesenchyme cross over
in organ development
What is the origin of ameloblasts ?
epithelial
What is the origin of odontoblasts ?
mesenchymal
How is the interaction between epithelium and mesenchyme mediated ?
cell signalling molecules
What is the enamel knot ?
signalling centre
determines the cuspation of the tooth
What happens to the enamel knot in the early bell stage ?
it divides depending on how many cusps the tooth has
eg. premolars- divide into 2
number of knots is number of cusps
What does the 1st pharyngeal arch divide into ?
mandibular and maxillary arch
What is the odontogenic potential ?
capacity to form teeth
What can potentially happen within 2 days ?
dental epithelium can loose its odontogenic potential
How does the odontogenic potential switch ?
from epithelial to mesenchyme
What type of signalling is there in the initiation stage ?
epithelial signallig which turns epithelium into dental mesenchyme
What type of signalling is there in the bud stage ?
mesenchymal signalling as epithelium looses its odontogenic potential
What do combinations of transcription factors do ?
regulate expression of signalling molecules
What is paracrine signalling ?
signalling molecules are secreted and act on nearby receptors
Give some examples of signalling molecules ?
Wnt family
Fgf- fibroblast growth factors
BMP- bone morphogenic proteins
What do transcription factors do ?
alter gene expression
Give some examples of transcription factors ?
Pax
Msx
What happens in the initiation stage signalling wise ?
competence to make tooth in the epithelium
FGF and BMP signals transmitted
expression of PAX9/MASX1 transcription factors
TFs lead to cells identifying as mesenchymal cells
What i the outcome of the initiation stage ?
tooth position
What happens in the bud stage signalling wise ?
odontogenic potential shifts to mesenchyme
mesenchyme secretes FGF and BMP
PAX9/MSX1 transcription factors made
How is the enamel knot formed ?
cells in the centre become arrested and dont divide
this happens in cap stage when BMP is secreted
What happens in the cap stage signalling wise ?
enamel knot secretes BMP arrests cell division
FGF induces cell proliferation in surrounding border cells - leads to downwards movement of enamel knot and formation of a 3D structure
What does the cap stage determine ?
tooth shape
How are signalling molecules used repeatedly ?
BMP and FGF are always present in tissue
they in turn stimulate MSX1 and PAX9 transcription factors
again stimulates BMP and FGF
What are genetic modules ?
they are reused to regulate subsequential development steps
Mutations in genetic regulators lead to what ?
arrest tooth development at an early stage
What do EDA1/EDAR mutations lead to ?
ectodermal dysplasia
What do PAX9/MSX1 mutations lead to ?
hypodontia
How does variable Shh expression lead to domains that determine tooth development ?
at the lamina stage shh expression can varied in different regions
leads to domains of cells that form a special structure
domains divide to determine tooth shape- primary enamel knot
further subdivision leads to secondary enamel knot to determine cusps
Which transcription factors code for the incisor region ?
MSX1/2
Which transcription factors code for the molar region ?
Dlx 1/2- maxillary molars
Dlx 5/6- mandibular molars
Barx
What would happen in an absence of Dlx1/2 ?
loss of maxillary molars
What would happen with an overexpression of barx-1 ?
in the incisor region the incisors would be transformed into molars
Defects in the initiation stage lead to ?
defects affect tooth number and identity
ectodermal dysplasia and hyperdontia
Defects in the morphogenesis stage lead to ?
defects in number, shape and size
hypodontia
Defects in the histogenesis stage leads to ?
hard tissue formation
amelogenesis imperfecta etc
What are syndromic defects ?
they occur in combination with other effects
What are non-syndromic defects ?
defects not associated with another abnormalities
What is hypodontia ?
less than 6 missing teeth excluding 8s
Which mutation leads to hypodontia ?
MSX1 mutation
What are common features of hypodontia ?
missing lower 5s
retained primary molars
missing lower 2s
incisors are peg shaped
What is oligodontia ?
more than 6 missing teeth excluding 8s
Which mutation leads to oligodontia ?
pax9 mutation
What are common features of oligodontia ?
missing 4s
missing 5s
missing molars
What is anodontia ?
no teeth
What are syndromes associated with oligodontia ?
hypohidrotic ectodermal dysplasia
rieger syndrome
oligodontia- colorectal cance syndrome
Which mutation leads to hypohidrotic ectodermal dysplasia ?
Eda1
Which mutation leads to rieger syndrome ?
Pitx2
Which mutation leads to oligodontia- colorectal cancer syndrome ?
Axin 2
How can we manage hypodontia ?
open spaces for bridges and implants
close spaces with orthodontic devices
Give an example of hyperdontia ?
cleidocranial dysplasia
Which mutation leads to cleidocranial dysplasia ?
RUNX2
What is cleidocranial dysplasia ?
bone defects in the clavicle
multiple teeth due to duplication of the dental lamina
enamel hypoplasia
delayed eruption
What are dentigerous cysts ?
radiolucency caused by a fluid filled space between REE and the tooth crown
Incomplete breakdown and removal of the dental lamina can lead to what ?
supernumerary teeth
eruption cysts
odontomes
What are eruption cysts ?
form when teeth try to erupt and hit epithelial remnants leading to pearls of serres
What is the gubernacular canal ?
canal filled with connective tissue that connects the dental follicle to the oral epithelium
What are the 3 types of amelogenesis imperfcta ?
hypoplasia
hypomineralisation
hypomaturation
What is hypoplasia ?
affects enamel matrix formation
reduced enamel thickness
What is hypomineralisation ?
normal enamel thickness but reduced mineral content
What is hypomaturation ?
normal enamel thickness but softer
Which gene is mutated in amelogenesis imperfecta ?
AMELX and ENAM
What is dentinogenesis imperfecta ?
defects in dentine formation
blue, gray, opalascent teeth
softer dentine leads to enamel chipping and tooth wear down
bulbous crowns
Which genes are mutated in dentinogenesis imperfecta ?
DSPP
How can dentine be classified ?
by location and time of development
What is predentine ?
unmineralised dentine matrix
forms between the layer of odontoblasts and the mineralising front
What is primary dentine ?
forms during tooth development
What is secondary dentine ?
forms after root completion
What is tertiary dentine ?
in response to stimuli
What is coronal dentine ?
in the crown
What are the 2 types of coronal dentine ?
circumpulpal and mantle
What is mantle dentine ?
outermost layer that forms first
What is circumpulpal dentine ?
bulk of the crown
What are the 2 types of root dentine ?
hyaline layer- outermost
granular layer of tomes
What is the composition of dentine ?
70% inorganic
20% orgaic
10% water
What is the inorganic component of dentine ?
calcium hydroxyapatite crystals
Where are the hydroxyapatite crystals located in dentine ?
between the type I collagen fibrils
What are the components of the organic matrix of dentine ?
type I collagen fibrils and some type III networks proteoglycans glycoproteins phosphoproteins growth factors
What are proteoglycans what do they do ?
they are GAGs with proteins attached
they regulate the mineralisation process
What are glycoproteins ?
osteonectin
osteopontin
dentine sialoprotein
What are phosphoproteins ?
dentine phosphoprotein
unique to dentine
What are growth factors ?
BMPs
transforming growth factors
What are the physical properties of dentine ?
softer than enamel higher tensile strength than enamel porous sensitive reactive less radiopaque than enamel
Why does dentine have a higher tensile strength than enamel ?
collagen fibrils resist shearing forces
Why is dentine sensitive ?
it is innervated by the pulp
Why is dentine reactive ?
tertiary dentine can be made in response to external stimuli
When does dentine formation begin ?
at the cusps in the late bell stage
Where do odontoblasts differentiate ?
in the cervical loop region from dental papilla cells
When do odontolasts differentiate ?
when signals from pre-ameloblasts induce differentation of dental papilla cells into odontoblasts and subodontoblasts
What happens when odontoblasts differentiate ?
they become columnar and secrete predentine
What are the steps of dentinogenesis ?
- odontoblasts secrete predentine
- Large type III collagen fibrils form perpendicular to the EDJ
- secretion of smaller type I fibrils parallel to the EDJ
- in mantle dentine- vesicles are secreted by odontoblasts- contain calcium phosphate
- odontoblasts develop cell processes
- initiation of mineralisation
- crystallites burst out from vesicles- for,m the mineralising front
What are von Korffs fibres ?
type III collagen fibrils that form perpendicular to the EDJ
How does mineralisation happen ?
via matrix vesicles
What are matrix vesicles ?
small membrane covered vesicles secreted by odontoblasts
What do matrix vesicles contain ?
Phospholipids that bind to calcium
Alkaline Phosphatase which increases phosphate concentration by destroying the inhiibtor of mineralisation- pyrophosphate
In which dentine are matrix vesicles only observed ?
mantle dentine
Where is predentine mineralised ?
at the mineralising front
Why does the thickness of predentine remain constant ?
the amount calcified is balanced by the addition of new unmineralised matrix
What are the 2 types of dentine mineralisation ?
linear and globular depending on speed
Which type of mineralisation happens in mantle dentine ?
globular
Which type of mineralisation happens in circumpulpal dentine ?
both linear and globular
Which mineralisation happens with fast dentine deposition ?
globular
Which mineralisation happens with slow dentine deposition ?
linear
What happens in globular calcification ?
calcospherites form in the matrix and fuse to form a single calcified mass
What are calcospherites ?
globular masses of mineralised matrix
What happens if calcification is exceptionally fast ?
the calcospherites dont fuse - leading to interglobular dentine
Where is interglobular dentine found ?
in the upper third of circumpulpal dentine
Why is the EDJ scalloped ?
increasing the SA and the attachment of enamel to dentine
What are enamel spindles ?
overshot odontoblast processes that enter the enamel and become trapped once the enamel mineralises
What is significant about dentine tubules in mantle dentine ?
they are highly branched increasing the sensitivity of dentine
What are the 2 types of dentine tubule curvature ?
S-shaped
Linear shaped
What are S-shaped dentine tubules ?
in the coronal region
crowding of odontoblasts means they are pushed apically
What are linear shaped tubules ?
in the cervical region and root dentine
little or no crowding of odnotoblasts
What is secondary curvature of dentine tubules ?
change in the direction of dentine tubules during dentien deposition
What are contour lines of owen and how are they formed ?
when secondary curvature coincides with adjacent tubules leads to an owen line
forms due to metabolic stress
What type of line is a contour line of owen ?
accentuated incremental growth lines
hypomineralised
What are von ebner lines ?
daily short period lines
they showcase daily dentine deposition - daily activity of odontoblasts
closely spaces
What are andresen lines ?
more spaced out than von ebner lines
long period
sharply defined
What is the most prominent growth line ?
neonatal line
Why does the neonatal line form ?
disturbance at birth in dentine deposition
What are the types of circumpulpal dentine ?
intetglobular
intertubular
intratubular
sclerotic
What is intertubular dentine ?
dentine between tubules
What is intratubular dentine ?
dentine inside tubules
What is sclerotic dentine ?
caused by obliteration of dentine tubules
What is reactionary dentine ?
original odontoblasts secrete dentine
less tubules
in response to weak stimuli
What is repairative dentine ?
newly recruited odontoblast like cells - original die
deposit dentine that is less structured
strong stimulus- fast repsonse
What is secondary dentine and where is it found ?
forms throughout life
reduces the size of the pulp chamber
found on roof and floor of pulp chamber
What are the features of intratubular dentine ?
lines the inside of dentine tubules
hypomineralised
What does continual formation of intratubular dentine lead to ?
obliteration of dentine tubules
dentine is now sclerotic
What are dead tracts ?
retraction of odontoblast processes and odontoblast cell death means that tubules become air filled and are visible as dark lines
How does sclerotic dentine increase ?
age
attrition
caries
The formation of sclerotic dentine is a mechanism for what ?
protection against microorganisms
What are the 2 different types of root dentine ?
tomes granualr layer
hyaline layer
What is the hyaline layer ?
non tubular
first layer formed
bonds dentine to cemnetum
hypomineralised
What is tomes granular layer ?
globules
incomplete fusion of calcospherites
How do ameloblasts form ?
odontoblasts send signals to IEE cells which induces differentaition to ameloblasts
What are the 3 phases of amelogenesis ?
presecretory phase
secretory phase
maturation phase
What are the 2 stages in the presecretory phase ?
morphogenetic stage
histodifferentation stage
What is the initial enamel layer like ?
aprismatic
30% mineralised
What are the 2 stages in the secretory phase ?
initial secretory sage
secretory stage
What happens in the morphogenetic stage ?
IEE cells are cuboidal
basal lamina made which separates the IEE cells from the dental papilla - differentiation to pre-ameloblasts
What happens in the histodifferentiation stage ?
differentiation of pre-ameloblasts to ameloblasts
cells are columnar, cell polarity and nucleus moves proximally
basal lamina removed
enamel proteins made
What is the purpose of tomes process ?
to orientate crystals
align prisms
What happens in the initial secretory stage ?
tomes process is absent
ameloblasts enlongate
and secrete the initial aprismatic layer of enamel
What happens in the secretory stage ?
tomes process is present
the proximal part develops before the distal part
proximal part produces interprismatic enamel
distal part produces prismatic enamel
Where is the distal portion of tomes process located ?
between the prismatic and interprismatic layer of the enamel
What happens when the outermost enamel layer is formed ?
the ameloblasts become shorter and loose the distal portion of tomes process
form thin aprismatic enamel
What are the 2 types of enamel proteins ?
amelogenins and non-amelogenin proteins
What are amelogenins ?
90% matrix content
hydrophilic- regulate growth and thickness of enamel
form nanospheres- collate between crystals to prevent them widening
scaffold for enamel structure
How are amelogenins removed ?
proteolytically cleaved selectively
What do mutations in enamelysin lead to ?
amelogenesis imperfecta
What are non-amelogenin proteins ?
first matrix component secreted but removed proteolytically
10% matrix contnet
What happens if non-amelogenin proteins arent removed ?
they form the enamel sheath at the periphery of prisms
only remaining organic material
What are 3 examples of non-amelogenin proteins ?
ameloblastin
enamelin
amelotin
What is ameloblastin ?
adhesion of ameloblasts to enamel matrix
What is enamelin ?
promotes and guides formation of enamel prisms
What is amelotin ?
basal lamina protein
adhesion of enamel to junctional epithelium
What are the 2 stages of the maturation phase ?
transitional stage
maturation proper
What happens in the transitional phase ?
enamel full formed
ameloblasts decrease in volume and 50% die by apoptosis
What happens in the maturation proper stage ?
increase in mineral content
water and proteins removed
increase in ion transport
Ameloblasts in the maturation phase are cyclically modulated between which 2 types ?
smooth ended
ruffle ended
What are ruffle ended ameloblasts ?
selectively transport calcium ions to the enamel layer
What type of junctions are in ameloblasts ?
leaky junctions at the basal end
tight jucntions at the enamel end to prevent fluid passage
What are smooth ended ameloblasts ?
leaky junctions at enamel end
allows water and enamel proteins to leave
IF travels between ameloblasts to neutrlaise increase in protons
deliver trace elements like fluoride to enamel layer
Which surface has the most mineralised layer of enamel ?
occlusal surface
degree of mineralisation decreases towards the EDJ
Why are primary teeth less mineralised ?
smaller maturation phase
How is mature enamel in a chemica equilibrium ?
acid leads to mineral loss
saliva acts as a buffer and is a permanent remineralising agent
What happens in the protective stage of amelogenesis ?
REE forms inactive cuboidal cells
cover crown and prevent crown from being resorbed
What does water fluoridation do ?
leads to fluoride incorporation
enamel becomes resistant and reduces dental caries
What does long term excessive consumption of fluoride lead to ?
fluorosis
mottled enamel
What are the features of enamel in fluorosis ?
faint white opacities
pitting
high porosity in outer third- bacteria can enter
What does acid etching do ?
makes it more adhesive for dental restorative materials
removes a thin layer of enamel to increase SA- better bonding surface
What are white spot lesions ?
loclaised demineralisation
can be arrested or progress to caries
What does tetracycline do?
disturb amelogenesis and can be incorporated into tissues - brown pigmentation
What is enamel hypomineralisation ?
smooth surface but abnormal colour
What is molar incisor hypomineralisation ?
affects teeth that form in first year of life
6s and incisors
What is the origin of enamel ?
epithelial origin
What is the composition of enamel ?
96% inorganic
4% organic
Where is enamel the thickest and thinnest ?
Thickest at cusps and thinnest at cervical region
How does enamel thickness increase in molars ?
increases in thickness from 1st to 3rd molar
What are the mechanical properties of enamel ?
hard
brittle
low tensile strength
What do HA crystallites combine to form ?
prisms
What are prisms separated by ?
interprismatic region
How is prismatic and interprismatic eamel different ?
they are similar in structuure but diverge in orientation
What are the 3 types of enamel prism patterns ?
circular
stacked
keyhole
Which pattern is found in humans ?
keyhole
What is the circular enamel pattern ?
discrete rods surrounded by interprismatic enamel
What is the stacked enamel pattern ?
rods in vertical rows
interrow sheets
What is the keyhole enamel pattern ?
head and tail
How many ameloblasts form each keyhole rod ?
5
What is the enamel prism sheath ?
boundary between prisms and interprismatic enamel
What material does the enamel sheath contain ?
ameloblastin
What is the direction of enamel prisms in primary teeth ?
orientated towards the oral cavity
What is the direction of enamel prisms in permanent teeth ?
towards the alveolar crest
What is prism decussation ?
enamel prisms follw a sinusoidal path
What is the purpose of enamel decussation ?
strengthen enamel structure
preventing cracks
What are hunter-schreger bands ?
alternating light and dark bands
due to prism decussation
longitudinally-parazones - light
transversally- diazones- dark
What is gnarled enamel ?
exaggerated prism decussation
rapid enamel formation
What are cross sriations?
result of daily variation
in ameloblast secretory rate
What are striae of retzius ?
result of ameloblast position at various points in development
long weekly lines
extend from the EDJ to the outer surface and externally as perikymata
What is linear enamel hypoplasia ?
disruption to enamel formation causes deep grooves on outer surface due to stressful development
What are enamel tufts ?
hypomineralised voids
located at the EDJ- project outwards
contain tuffelin
if they stretch into enamel theyre lamellae
What is erosion ?
dissolution of enamel by acids that arent of bacterial origin- can be intrinsic ot extrinsic
irreversible tooth loss
Removal of carbonate and phosphate ions leads to which type of structure ?
honeycomb - prisms dissolved
interprismatic enamel more prominent
Where is the pulp derived from ?
mesenchymal cells of the dental papilla
What is the pulp divided into ?
coronal
radicular
What does the pulp open into ?
The PDL via the apical foramen
What is transmitted by the apical foramen ?
blood vessels
nerves
lymphatic vessels
What is the pulp made of ?
ECM
blood vessels and lymph vessels
cells
What is the composition of pulp ?
75% water
25% organic
What are the histological zones of pulp ?
predentine- unmineralised odontoblast layer cell free zone - ECM and nerve endings cell rich zone - fibroblasts pulp core - nerve endings and blood vessels
Why are their tight junctions and desmosomes between odontoblasts ?
maintain spatial relationships
stop substances from the pulp entering the dentine
Why are their gap junctions between odontoblasts ?
cell to cell communication
exchange of small molecules
What is the most abundant cell type in the pulp ?
fibroblaasts
What do fibroblasts do ?
prodcue collagen and ground substance
can also degrade collagen to remodel tissues
What are fibroblasts like in young pulp ?
large
centrally located nucleus
What are fibroblasts like in old pulp ?
spindle shaped
smaller
What are the types of cell in the pulp ?
fibroblasts
undifferentiated mesenchymal cells
immune cells
dental pulp stem cells
What ca undifferentiated mesenchymal cells do ?
differentiate into odontoblast lie cells and fibroblasts
number reduces with age and this reduces the repairative potential
Which immune cells are present in the pulp ?
macrophages
T and B lymphocytes
Neutrophls and eosinophils
dendritic cells
What is the role of pulp macrophages ?
patrol pulp and remove dead cells and bacteria
What is role of T and B lymphocytes ?
adaptive immunity from antibodies
What do neutrophils and eosinophils do ?
respond to infection
mediate inflammation
What do dendritic cells do ?
present foregin antigens to T cells
What does the ECM of the pulp contain ?
type I and III collagen fibres
ground substnace
What is the purpose of collagen in the pulp ?
forms a scaffold
What is the ground substance of the pulp ?
non protein fibrous matrix
GAGs, Proteoglycans, Glycoproteins and water medium for transport
reservoir for growth factors
Why does the ground substance contain hydrophilic molecules ?
swell when hydrated
hydrogel made that fill extracellular spaces
Where do blood vessels in the pulp originate from ?
PDL
Why are there lymphatic vessels in the dental pulp ?
drainage of tissue fluid
have thin walls and no RBCs
What are the 2 types of nerve s in the pulp ?
myelinated afferent
unmyelinated C fibres
What is the role of unmyelinated afferent fibres ?
from v2/v3
transmit pain sensation to the CNS
cell bodies in the trigeminal ganglion
What is the role of unmyelinated C fibres ?
afferent- terminate in odontoblast layer and transmit noxious timuli
efferent- to smooth muscle in arterioels to control capillary flow
What is the plexus of raschkow ?
a nerve plexus that terminates at the cell free zone
What is the function of the pulp ?
provide vitality to the tooth
nourishment of odontoblasts
sensation
barrier
What is the pulp chamber like for young teeth ?
large pulp chamber
thin dentine so pulp easily exposed
What is the pulp chamber like in young teeth ?
narrow pulp chamber
challenge for RCT
How can caries spread ?
from the pulp to the periodontal tissues leading to periodontal abcesses
How can periodontal disease spread ?
from the periodontal tissues to the pulp via accessroy root canals
What is a pulpectomy ?
partial RCT
access pulp chamber and remove pulp tissue
What is RCT ?
pulpectomy
cleaning and shaping
disnfectant
sealing material
Why do pulp stones form ?
age
caries - chronic stimulus
What are false pulp stones ?
calcifying blood vessels
contain bone like material
What are true pulp stones ?
detatched odontoblasts
contain dentine
What are the 3 theories of dentine sensitivity ?
neural theoery- dentine directly innervated
receptors- odontoblasts are receptors
hydrodynamic theory- fluid movement in dentine tubules is sensed directly
When does root formation happen ?
After crown completion
After crown completion has occurred what happens to the epithelial cells of the OEE and the IEE ?
they proliferate from the cervical loop of the enamel organ to form a double layer of cells- Hertzwigs epithelial root sheath
What does HERTS do ?
extends around and encloses the pulp and determines the future shape of the root.
What is different between the cervical loop and the HERS ?
no stratum intermedium or stelale reticulum
What epithelial signalling occurs in the HERS ?
transient enamel proteins
signalling the dental follicle to make osteoblasts that resorb bone and allow tooth eruption
What mesenchymal signalling occurs in the HERS ?
cementoblast differentiation and periodontal regeneration
What does the IEE of the HERS induce ?
odontoblast differentiation
odontoblasts secrete predentine which is mineralised to root dentine - single root tooth made
What is the curved end of HERS ?
epithelial diaphragm
outlines the primary apical foramen
Growth of the dentine layer does what do HERS ?
HERS is stetched and the epithelial cells degenerate
HERS has a network appearance
What happens during root completion ?
growth of HERS
odontoblast differentiation
dentine formation
Why does HERS remain stationary ?
the epithelial cells dont grow downwards
What happens if HERS is stationary ?
root dentine is formed and the root is pushed upwards
however disproven as rootless teeth can erupt
How else are roots erupted ?
collagen fibres rearranged - pull tooth up
What is different about root dentine compared to coronal dentine ?
root dentine has collagen fibres that are parallel to the ECJ
less mineralised due to less dentine phosphoprotein
What does dentine phosphoprotein do ?
binds to calcium and regulates dentine mineralisation
Where is HERS ?
skirt hanging from the enamel organ
encloses the primary apical foramen
How does the secondary apical foramena form ?
primary apical foramen divides by fusion of epithelial cells
How can 3 roots form ?
triangular HERS fusion
At the end of eruption how long is the root ?
65% of the final length
wide, open and root apex
How long do primary teeth take to complete their roots ?
1.5 years
How long do permanent teeth take to complete their roots ?
3 years
What happens to the apical foramen when the roots are complete ?
the foramen is narrow and blood vessels and nerves pass through
What happens in cemntogenesis ?
odontoblasts differentiate and produce dentine
HERS stretches and is disintegrated
differentiation of dental follicle cells into
osteoblasts
fibroblasts
cementoblasts
What do fibroblasts do ?
produce colalgen for the PDL
What do osteoblasts do ?
resorb bone for eruption
What are the 2 theories of cementoblast differentiation ?
- undifferenitated dental follicle cells migrate through gaps in disintegrating HERS - receive inductive signals
- HERS cells undergo epithelial- mesenchymal transition
What is cementum ?
avascular connective tissue covering roots
What is the function of cementum ?
attaches the root dentine to the PDL
What is the chemical composition of cementum ?
45-50% hydroxyapatite
gives resistance to root resorption
What are the types of collagen in cementum ?
type I III
XII
Which non collagen proteins does cementum contain ?
bone sialoprotein
Alkaline phosphatase
How do we classify cementum ?
acellular- primary
cellular- secondary
What are the types of relationship between enamel and cementum at the CEJ ?
cementum overlaps enamel - 60%
cememtum meets enamel- 30%
cementum and enamel dont meet- 10%
What is acellular cementum ?
covers the part of the root adjacent to the dentine- it provides attachment to the PDL
What is cellular cementum ?
founs apically and in interradicualr areas for adaptation and repair thickness increases with age fast rate of development incremental lines are far apart
Why do cementoblasts processes face the PDL ?
to nourish the cementoblasts
How is early acellular cementum made ?
cementoblasts align along the hyaline layer
extension of the cell processes into predentine
deposition of collagen fibres - intemingling of predentine
form fibrous fringe
some of the collagen fibres extend and stitch to the fringe
mineralisation of the dentine- processes are trapped
What is the singnificance of cementoblast processes being trapped ?
they strengthen the attachment of dentine and cementum
What are the lines of salter ?
incremental growth lines in cementum
show daily activity of cementoblasts
What are cementricles ?
groups of cementoblasts that are separated and sit in the PDL
acellualr and have concentric rings
What are epithelial cells of malassez ?
HERS is stretched
degenerates by apoptosis leaving behind groups of cells in the PDL
What are enamel pearls ?
epithelial rests can form enamel pearls
What are the 2 theories of enamel pearl formation ?
cell rests attach to predentine in the absence of cementoblasts
root bifurcates and molecular signals induce ameloblast differentiation
HERS development is initiated and stratum intermedium and stratum reticulum become trapped in the ECRs
What is concresence ?
union of 2 teeth in eruption
due to fusion of cementum surfaces
usually 7s and 8s
Why does concresence come about ?
trauma
crowding
What are dilacerated roots ?
curved and bent roots
due to developmental trauma
extraction is difficult
Why do multiple roots and canals form ?
abnormal folding of HERS
disturbances in the closure of primary apical foramina
What needs to be considered when treating teeth with excess canals ?
need to be aware of extra canal- if not cleaned can be a source of recurrent infection
What is the mechanism of lateral root canal formation ?
HERS disrupted
blood capillary forms between dental papilla and follicle
odontoblast formation- dentine made for new canal
Where are accessory root canals mostly found ?
in the apex
What is hypercementosis ?
abnormal production of cellular secondary cementum
can be due to trauma or age related
What are the implications of hypercementosis ?
increased distance from the CEJ to the root apex
endodontical implications
Which teeth would the neonatal line be present in ?
all primary teeth and the 6s
What would be the position of the neonatal line in the D and E ?
in the D- neonatal line further away from the EDJ- more development time
in the E- neonatal line closer to the EDJ- less development
Why do we need to know prism decussation ?
clinically for restorations
Why does the neonatal line form ?
birth shuts down ameloblasts- ameloblasts freeze- shows position at birth
How do dental follicle cells differentiate ?
the dental follicle cells migrate through gaps in the disintegrating HERS-attach to the predentine and get signals to initiate odontoblast differentation.
Why does the stellate reticulum move downwards in the late bell stage ?
protect the pulp
What happens in coordinated root and PDL development ?
odontoblast induction and dentine formation
stretching and disintegration of HERS
Differentiation of dental follicle cells
What do the dental follicle cells differentiate into ?
cementoblasts- cementum
fibroblasts- collagen
osteoblasts- bone
What are the genetic factors regulating periodontal development ?
FGFs carry out cell proliferation
BMPs carry out bone formation and cell differentiation
GFs stimulate periodontal regeneration
What are the functions of the PDL ?
tooth attachment withstand masticatory forces sensory receptor remodelling nutritive fucntion
What does the PDL do with tooth attachment ?
PDL fibres insert into the cementum and the alveolar bone to form a fibrous gomphosis joint with no movement
How does the PDL withstand masticatory forces ?
acts as a shock absorber
How can the PDL act as a sensory receptor ?
can sense pain tension and compression
What does the PDL do in remodelling ?
during tooth eruption - high turnover of ECM and collagen fibres-
What does the PDL do with nutritive function ?
hughly vascularised tissue
connected to dental arteries to get nutrients
What happens in PDL development in the initiation stage ?
ligament space between cementum and and bone consists of unorganised tissue
What are short fibre bundles ?
formed near the cementum and bone and extend only a little bit into the ligament space
What are fine brush fibres ?
emerge from the cementum and only a few fibres emerges from the bone into the ligament space
How is an interconnected meshwork formed in the PDL space ?
fibroblasts produce more collagen fibrils that assemble as fibres and gradually conenct on both sides to form an interconnected meshwork
What are the fibres like on the alveolar bone side ?
thick and wide spread
What are the fibres like on the cementum side ?
thin and closely spaced
What are alveolar rest fibres ?
formed first at the CEJ
initially oblique then horizontal and the oblique again
When is the PDL constantly modified ?
in tooth movements and occlusion
What are the principle fibre groups ?
alveolar crest group horizontal group oblique group apical group interradicular group
What is the alveolar crest group ?
below CEJ
rim of alveolus
resits extrusive forces
What is the horizontal group ?
below the alveolar crest group
at right angle to the tooth axis
resist horizontal forces that could make the tooth tip
What is the oblique group ?
most abundant fibre group
resists intrusive mastication
What is the apical group ?
radiate from the root apecx
form the bone of the socket
resist extrusive forces
What is the interradicular group ?
only in multi rooted teeth
connects to the crest of the interradicular septum
resist extrusive forces
What does each collagen fibre look like ?
spliced rope of individual fibrils that are continuously individual fibrils are remodelled whilst the overall fibre remains in place
What are the elastic fibres in the PDL ?
oxtytalan fibres that contain fibrillin and are perpendicular to collagen fibres in cervical region
What do the elastic fibres do ?
associated with NV bundles
form 3D meshwork surrounding the root
What are sharpeys fibres ?
mineralised PDL fibres in the alveoalr bone and cementum
What is the main function of finroblasts ?
produce collagen fibrils that turn into fibres and the ECM
What are the types of fibroblasts ?
perivascular and endosteal (bone)
What do fibroblasts do ?
secrete GFs and cytokines
high amount of collagen
Do fibroblasts have a high or low turnover ?
high
Which junctions are in fibroblasts ?
adherens junctions
gap junctions
What does the cytoskeleton in fibroblasts allow them to do ?
migration and motility
How are fibroblasts contractile ?
bind to the ECM via integrins
How is fibroblast activity induced ?
mechanical and masticatory forces
What is the dual function of fibroblasts ?
synthesis
degradation- of ECM and collagen
Which enzymes are responsible for high collagen turnover in periodontal disease ?
matrix metalloproteases
What are osteoclasts and osteoblasts invovled in ?
bone remodelling of alveolar bone
Which immune cells are present in the PDL ?
eosinophils
mast cells
macrophages
What are other cell types in the PDL ?
cementoblasts
rests of mallasez
undifferentiated mesenchymal cells
endothelial cells
How do the superior and inferior alveolar arteries enter the pulp ?
the apex
Which arteries supply the PDL ?
superior and inferior alveolar arteries
interalveoalr arteries
lingual and palatine arteries
What are the interalveoalr arteries ?
pass through the alveolar bone
known as perforating arteries
What do perforating arteries do ?
form interstitial areas with the PDL
enable the PDL to function after endodontic treatment
`What are the perforating arteries ?
part of the NV bundle that passes through the alveolar bone and form interstitial areas with the PDL
What are interstitial areas ?
located closer to the alveolar bone and contain NV bundles
What do blood vessels do around the root ?
form a circular capillary plexus around the root surface a and a postcapillary plexus from which venules pass to the bone
Which direction do blood vessels run ?
apical occlusal direction and form anteriovenous anastamoses
What is the crevicular plexus ?
surrounds the tooth in the region beneath the gingival crevice
Why are capillaries fenestrated in the PDL ?
fenestrations are pores in the endothelial cells
increase diffusion capacity needed for high metabolic rate in PDL
What do perforating nerve fibres divide into ?
gingival and apical branch
Which teeth have a higher PDL innervation than molars ?
upper incisors
What are the 2 types of nerve fibres in the PDL ?
sensory and automatic
What do sensory PDL fibres do ?
detect pain
mechanically respond to pressure
alter tongue and neck muscles
What do autonomic PDL fibres do ?
regulate blood flow through constriction and dilation of blood vessels
What are the types of nerve endings ?
free endings
ruffini corpsucles
colied type
encapsualted spindle type
What do free endings do ?
tree like
unmyekinated
extend to cementoblasts
sense pain and pressure
What do ruffini corpuscles do ?
found in the PDL root apex
myelinated
dendritic endings
sense pressure
Where are coiled type nerve endings found ?
middle third of PDL
What are encapsulated spindle type endings ?
found in the PDL root apex
surrounded by a fibrous capsule
Where is the PDL thinnest ?
middle third of the root
How does PDL thickness change ?
decreases with age
What doe mastication induce ?
periodontal remodelling
increased PDL with
increased alveolar bone size
Where is the PDL thicker ?
in areas of tension than compresssion
What does a decreased use of PDL lead to ?
reduction in the periodontal tissues
What can strong orthodontic forces lead to ?
lead to PDL necrosis
How can a damaged PDL be repaired ?
cells
What does failure to repair the PDL lead to ?
localised resorption
tooth ankylosis
What is tooth ankylosis ?
fusion of the tooth to the bone
How can the PDL be a target for periodontal surgery ?
prevent undesirable wound healing
GFs, cytokines, stem cells stimulate PDL regenration
What is the composition of the PDL ?
60% ground substance
collagen fibrils blood vessels and nerves
What is the composition of the fibres in the PDL ?
90% collagen
10% oxytalan
Which types of collagen are dominant ?
type I
type III
What is oxytalan ?
fibrillin molecules without elastin
What does collagen type III form ?
reticular fibre meshwork
What does collagen type XII form ?
present after development and link collagens together
Does collagen composition change with age ?
no
What is the ground substane known as ?
ECM
What does the ECM contain ?
GAGs
proteoglycans
glycoproteins
What are some examples of GAGs ?
hyaluronic acid
dermatan sulfate
What are the functions of the ground substance ?
act as a shock absorber
orientate collagen fibrils
increase hydration
increase collagen strength
What does fibronectin do ?
mediates collagen fibril attachment to cells via integrin dimers
influence cell differentiation and migration
What does the ECM bind ?
GFs and cytokines
What are lines of salter ?
daily activity of cementoblasts - incremental growth lines
How do odontoblasts come about in root formation ?
IEE of the HERS induces odontoblast differentiation
What does acellular cementum do ?
covers the root and attaches to the PDL
How does a cellular cementum form ?
cementoblasts align to the hyaline layer and their process extend into the dentine - collagen fibrils are secreted and become trapped when mineralisation happens
What do capillaries in the dental follicle supply ?
supply nutrients to the SI and ameloblasts
What happens in initial enamel secretion ?
secretion of a thin aprismatic layer
30% mineralised
tomes process is absent
Why does stellate reticulum moves downwards in late bell stage ?
protect developing areas that arent mineralised
Which lines are accentuated ?
in dentine- contour lines of owen
in enamel- striae of retzius
Why does the granular layer of tomes form ?
incomplete fusion of calcospherites
extensive branching of odontoblasts
hypomineralised
Why does peritubular (intratubular) dentine form ?
increasing age. mild attrition
Is peritubular dentine hypomineralised or hypermineralised ?
hypermineralised
Where is the position of the neonatal line in the D ?
further away from the EDJ as more tissue formation
Where is the position of the neonatal line in the E ?
closer to the EDJ - less hard tissue
How can epithelial rests of malassex contribute to PDL and cementoblast formation ?
EMT
What is the primary curvature of dentine tubules ?
sigmoid route of dentine tubules
What is secondary curvature of dentine tubules ?
meandering at high magnification
What are the functions of the Stratum intermedium ?
alkaline phosphatase- enamel mineralisation
removaal of waste products
support ameloblasts
What does the stellate reticulum contain ?
GAGs for protection
What is the shape and function of OEE ?
cuboidal
tooth shape and exchange
What is the EDJ like in primary teeth ?
less scalloped as it forms faster
What is the clinical significance of enamel prism orientation ?
need to know direction so you dont undercut them - can release restorations
Which direction do primary enamel prisms orientate in ?
occlusally
Which direction do permanent enamel prisms orientate in ?
apically
Are prisms straighter or more curved in primary teeht ?
straighter
What does the distal portion of tomes process secrete ?
prismatic
What does the proximal portion of tomes process secrete ?
interprismatic
How does mantle dentine form ?
matrix vesicles- globular calcification
What in unique about mantle dentine ?
no dentine phosphoprotein
loosely packed with von korff fibres
highly branched dentine prevent crack propagation
What does amelobalstin do ?
adhesion of ameloblasts to enamel
What does enamelin do ?
guide formation of enamel crystals
What does amelotin do ?
adhesion of enamel to the junctional epithelium
What does the neonatal line signify in enamel and dentine ?
enamel- position of ameloblasts at birth
dentine- position of mineralising front
When is the first histological appearance of enamel and dentine ?
late bell stage
When are calcium ions actively transported during maturation stage ?
maturation stage with ruffle ended ameloblasts
Which gene family encodes transcription factors ?
MSX
Where are accessory root canals mostly found ?
apex
Which teeth are mostly affected by a PAX9 gene mutation ?
permanent molars
What percentage of people have cementum overlapping the enamel ?
60%
What percentage of people have cementum meeting enamel ?
30%
What percentage of people dont have cementum meeting the enamel ?
10%
What is secondary dentine ?
develops after the root is complete
reduces the size of the pulp chamber and root canals
How can we see secondary dentine ?
visible change in dentine tubule direction
found on roof and floor of pulp chamber
What does secondary dentine do ?
it forms throughout life by odontoblasts that line the pulp cavity
What does the alveolar process of the mandible form ?
tooth sockets
What are the mechanisms of bone formation ?
endochondral ossfication
intramembranous osssification
sutural ossification
What is endochondral ossification ?
chondrocytes produce cartilage
bone is made from the cartilage
osteoblasts replace cartilage with osteoid
What is intramembranous ossification ?
bones made from osteoblasts that differentiated from mesenchymal stem cells
What is sutural ossification ?
similar to intramembranous
fibrous connection providing stability during growth
What is the chemical composition of bone ?
67% inorganic hydroxyapatrtite between collagen I fibris
33% organic
What are the non collageneous proteins present in bone ?
bone sialoprotein
osteocalcin
osteonectin
osteopontin
What is the role of non collagenous proteins in bone ?
they bind to calciuim and control mineralisation
What are the functions of bone ?
support
protection
locomotion
mineral reservoir of calcium and phosphate
What does PTH do to bone ?
decrease bone formation
What does calcitonin do to bone ?
increase bone formation
What does vitamin D do to bone ?
increases bone formation
What does oestrogen do to bone formation ?
increase bone formation
What do glucocorticoids do to bone formation ?
decrease bone formation
What does leptin do to bone formation ?
increase bone formation
What is woven bone ?
forms during development
randomly orientated colalgen fibrils
remodelled into lamellar bone
What are the components of adult bone ?
compact bone
trabecular bone
What is compact bone ?
dense outer area of bone
What is trabecular bone ?
canceollous
spongy cavity filled with bone marrow
network of bone platees
What are the types of bone lamellae ?
cicumferetnial
concentric
interstitial
What are circumferential lamellae ?
enclose entire outer and inner perimeter of the bone
What are the concentric (haversain) lamellae ?
form basic unit of bone
make up bulk of compact bone
What is the structure of concentric lamellae ?
concentric rings with blood vessel in the middle
What is the basic unit of bone ?
osteon
What is an osteon ?
cylinder of bone that has a central canal which includes blood capilalreis used by osteoblasts
What is the periosteum ?
external connective tissue membrane consisiting of 2 layers
outer fibrous layer- dense collagen fibrils
inner fibrous layer- osteoblasts
What is the endosteum ?
loose connective tissue
separates bone surface from the bone marrow
not that active in bone formation
What are osteoblasts ?
bone forming cells
What is the morphology of osteoblasts ?
active- cuboidal
inactive- flat
What are osteoblats derived from ?
mesenchymal stem cells
What are the fucntions of osteoblasts ?
synthesis alkaline phosphatase
synthesis bone matrix
produce growth factors
What is the role of alkaline phosphatase in tooth development ?
cleaves inorganic phosphate to initiate and promote mineralisation
Which growth factors do osteoblasts produce ?
IGF1
TGF-
PDGF
What is the role of PDGF ?
increases bone repair and used in periodontal therapy
What are osteocytes ?
osteoblasts that are trapped in the bone amtrix
become smaller in size and produce a lacunae space
What do osteocytes produce ?
network of cellular processes that connect osteocytes- canaliculi
What is the fucntion of osteocytes ?
form sensors of the changing bone environment
form signalling centres to maintain bone integrity
What are osteoclasts ?
bone resorbing cells
produce howships lacunae
produce acid phosphatase and lysozymes
What is the morphology of osteoclasts ?
large and multinucleated
What are howships lacunae ?
resorption bays
What is the resorption sequence ?
osteoclasts attach to bone
create an acid environment
degrade exposed matrix
endocytosis of degradation products
What is intramembranous ossification ?
mesenchymal cells of the cellular periosteum - osteoblasts produce woven bone
remodelled to lamellar bone
formation of osteons by osteoblasts
continued bone replacement produces orgnaised mature bone with develope osteons and circumferential lamellae
What are the steps in the development of the alveolar process ?
1) mandible forms a trough under the inf alveoalr nerve and the alveoalr pocess grows towards the tooth germ
2) alveolar process surrounds the tooth germ and the inf alveoalr nerve is now in a bony canal
3) to accomodate the growing tooth germ and stellate reticulum the bone must be resorbed on the inner wall and deposited on outer wall
What are bone lining cells ?
flat cells
form an area of bone inactivity
area protected from resorption
source of progenitor cells
What are the stags of bone remodelling ?
resorption
reversal
formation
cessation
What happens in resorption ?
recruitment
migration and activation of osteoclasts
What happens in reversal ?
cessation of resorption
osteoclasts disappear- apoptosis and migration
What happens in formation ?
recruitment and migration of osteoblasts
What happens in resting ?
cessation of bone formation
surface covered by bone lining cells
What are the structural lines in bone ?
resting and reversal lines
What are resting lines ?
osteoblasts stop bone formation
lines form showing pauses in deposition
parallel
What are reversal lines ?
scalloped
change from resorption to formation
What are the plates in the tooth sockets ?
buccal cortical plate
lingual cortical plate
alveolar cibriform plate
What is the alveolar cribriform plate ?
has peroforations for blood vessels and nerves
What is the interdental septum ?
alveolar spetum between 2 teeth
What is the interradicular seprum ?
between 2 roots
What are the 3 parts of the alveolar process ?
cortical plate
spongiosa
alveolar plate
What is the cortical plate ?
surface layer or lamellar bone supported by osteons
thinner in maxilla than amndible
Where is the cortical plate the thickest ?
buccal aspect of the 4s and 5s lower
What is the spongiosa ?
trabecular bone
bone marrow spaces rich in adipose tissue
absent in anterior teeth as the alveolar and cortical plate is fused
What is the alveoalr plate ?
made of lamellar and bundle bone
contains sharpeys fibres
What is bundle bone ?
innermost layer of alveolar plate
contains collagen fibres of the PDL- sharpeys
What is the purpose of the bundle bone ?
provides attachment for the PDL fibres
What happens in the process of tooth drift ?
- resoprtion on the right side of alveolar bone- creates space for the tooth to move into
- bone must be formed on the cortical plate to compensate
- bone depostion on the cortical side
- excess bone must be resorped on the cortical side
Why is there no bone displacement ?
alveolar bone remodelling proceeds at same time
What is the concept of mesial drift ?
unworn teeth have few contact points
attrition causes loss of interproximal and occlusal surfaces
increase in interproximal distance made up for by mesial drift
leads to broader interproximal contact points
What is the link between abrasive diets and eruption of the 8 ?
in the past abrasive diets led to attrition and mesial drift
creating space for the 8 to erupt
softer diets in modern populations mean higher incidence of 8 impaction
What is ankylosis and what causes it ?
dental trauma or infection can lead to fusion of the totoh to the bone
prevents exfoliation
impaction of the successor
Which teeth are likely to be ankylosed ?
D and E
4 and 5 imapcted
What does further growth and submergence lead to ?
submergence of an ankylosed tooth- infraocclusion
What is the alveolar plate referred to on radiographs ?
lamina dura
Why is the alveolar plate radioplaque ?
thick cortical plate
What does an interrupted dark lamina dura indicate ?
periapical abscess
What can happen to the alveolar bone following extraction and periodontitis ?
resorption
dental implants hard to place
ability to make removable prostheses decreases
Which roots are in close proximity to the maxillary sinus ?
4 and 5 roots
What can happen during extraction to the maxilalry sinus ?
bone can fracture leading to a fistula
What happens in the tooth socket after extraction ?
fills with blood forming a blood clot
What can happen when the blood clot detaches ?
dry socket
alveolar ostelitis
alveolar plate exposed
painful bone inflammation
What is the gingiva ?
part of the oral mucosa that surrounds the teeth and the alveolar bone
What happens during tooth eruption to establish the dgj ?
the REE fuses with the oral epithelium to establish the DGJ
What does the junctional epithelium do ?
attaches tooth to gingiva
What happens when the DGJ is formed ?
tooth approaches oral epithelium and only a thin connective tissue layer separates the REE from the OE
fusion of the OE and the RR- degeneration of central epithelilal cells
DGJ is formed
What type of epithelium is the REE ?
simple epithelium
What type of epithelium is the OE ?
stratified squamous
Why is there no bleeding in eruption ?
epithelial continuity ensures no bleeding
What is the first stage of DGJ formation ?
immediately after tooth eruption
junctional epithelium is entirely REE
not keratinised and attaches firmly to enamel
What is the second stage in DGJ formation ?
gingival epithelium in the upper region overgrows the REE
create gingival sulcus made of sulcualr epithelium
junctional epithelium in the lower region is simple, non keratinised and appears like REE
What are the characteristics of gingival epithelium ?
stratifed
keratnised
What are the characteristics of sulcar epithelium ?
stratified
non keratnised
How is the base of the sulcus determined ?
masticatory forces
What is the external landmark of the base of the sulcus ?
free gingival groove
What is the third stage of eruption ?
gingival epithelium completely replaces the REE
small epithelial tag develops from the REE- Nasmyths membrane
What are the components of nasmyths membrane ?
primary enamel cuticle and cell remnants
What do molecular markers dictate about junctional epithelial and gingival epithelial cells ?
they are different
What is the immunohistochemical evidence behind the difference in junctional and gingival epithelial cells ?
staining for amelotin
amelotin normally expressed in ameloblasts but found in junctional epithelial and internal basal lamina
suggests junctional epithelium is derived from REE
What are the histological characteristics of attached gingiva ?
lamina propia- long papillae with dense collagen fibres
has a mucoperiosteum
no submucosa
What is the mucoperisoteum ?
fibrous connective tissue to the bone for stability
dense collagen fibres directly joint to to the periosteum of the bone
in the masticatory mucosa
difficult to inject- doesnt require sutures
What is the alveoalr submucosa ?
lose and mobile connectve tissue with few colalgen fibres
lamina propia is cellular
Which gingival fibres are visble in the buccal view ?
transseptal fibre group
What is the transspetal fibre group ?
runs interdentally from the CEJ of one tooth over the alveoalr crest to the CEJ of the neigbouring tooth
connects all teeth in the jaw and controls mesial and distal spacing
What is post retention relapse ?
in retetnion phase of orthodontic treatment the fibres are not remodelled quickly enough so the teeth move into original position
What do epithelial cells attach to which connects to the enamel proteins ?
epithelial cells secrete primary enamel cuticle - internal basal lamina onto the enamel - binds to to enamel proteins
How do epithelial cells attach to the primary enamel cuticle ?
via hemidesmosomes
What is the external basal lamina ?
attaches to the lamina propia - conenctive tissue
Why is the junctional epithelium permeable ?
reduced number of desmosomes and large intracellular spaces
What do large spaces in the junctional epithelium allow fo ?
GCF passage
What does GCF contain ?
immunoglobulin molecules complement factors macrophages exfoliated sulcar and junctional epithelial clls cytokines and metalloproteases
What is the purpose of the GCF ?
defence agaisnt bacteria
remove inflammed tissue
overproduction leads to tisseu degradation and periodontitis
What is the GCF indicative of ?
periodontal health
What is the attached gingiva ?
tightly attached to tooth and alveolar bone
What is the alveolar mucosa ?
loosely attached to the alveoalr bone and has sub mucosa
What is the free gingiva ?
not bound to other tissue
What is the free gignival groove ?
mark position of the gingival sulcus
What is the mucogingival junction ?
boundary between alveolar mucosa and attahced gingiva
What are the characteristics of the alveoalr mucosa ?
lining non keratinseid dark pink translucent thin - can see blood vessels
What are the characteristics of attached gingiva ?
part of masticatory mucosa
parakeratinised/ partially otho
light pink
stippled
What is the dentogingival fibre group ?
connects cervical cementum to lamina propia of free and attached gingiva
What is the alveogingival group ?
connects bone of alveolar crest to lamina propia of free and attached gingiva
What is the dentoperiosteal group ?
run from cementum outer surface to alveolar process or mylohyoid
What is the circular group ?
band around neck of tooth and interlaces with other fibres in free gingiva
binds free gingiva to tooth
What is the dental col ?
in the gingiva between the teeth- not attached to enamel
What is gingivitis ?
mild periodontal inflammation
dental plaque accumulation causes inflammatory response
70% collagen fibres destroyed in 3-4 days
treatment stops spread to PDL and alveolar bone
What does chronic inflammation lead to ?
destruction of connective tissue by inflammatory cells
apical migration of junctional epithelium
formation of gingival pocket
loss of PDL and alveolar bone
How can we prevent junctional peithelium migration ?
insertion of membrane
forms a fibrin clot against root surface and allows tissue regeneration
What is guided tissue regeneration ?
membrane inserted and when removed shows damged epitelium, mild inflammation and healthy fibrous tossue apically
What is the size of healthy periodontal pockets ?
0.5-2 mm
What is the size of diseased pockets ?
3 mm +
What is the oral mucosa ?
forms a continuim with the gingiva and tooth attachment tissues
What are the oral epithelium and epidermis derived from ?
embryonic ectoderm
What is the buccopharyngeal membrane ?
where the ectoderm and endoderm meet
What is the oral vestibule ?
space between lips, cheek, bone and teeth
What is the vestibular fornix ?
trough formed through the vestibule
What is the upper labial frenulum ?
fold of alveolar mucosa that attaches to the labial mucosa
Which 2 frenulum are present in the mouth ?
frenulum near the maxilalr molars
upper labial frenulum
What is the midline diastema ?
large labial frenulum attaches to the alveoalr crest
creates a diastema between maxillary 1s
affects the stability of dentures
What is the oral cavity proper ?
separated from the vestibule by the teeth
What is the anterior pillar of fauces ?
palatoglossal fold
What is the posterior pillar of fauces ?
palatopharyngeal fold
What is the palatine tonsil ?
lymphoid tissue tonsils
What is the uvula ?
midline projection from soft palate
What is the soft palate ?
muscular extension of the hard palate
is mobile and not attached to bone- used for swallowing, taste and speech
What are the 2 components of the oral mucosa ?
epithelial and mesenhcymal component
What are the functions of the oral mucosa ?
mechanical protection - protection from masticatory forces
barrier from microorganisms
immunological defence
lubrication and buffering - saliva
sensation - touch, pain, taste and proprioception
What is the lining mucosa ?
60% alveolar mucosa soft palate lip buccal mucosa floor of mouth underside of tongue
What is the masticatory mucosa ?
25%
gingiva and hard palate
What is different about masticatory mucosa ?
it has a mucoperiosteum
lamina propia more fibrous and directly attached to the mucoperiosteum of the bone
What is the specialised mucosa ?
15%
tongue
What are the 3 components of the oral mucosa ?
oral epithelium
lamina propia
submucosa
What are the chracteristics of the oral epithelium ?
stratified squamous epithelium
epithelial ridges- pegs
keratinocytes
What are the characteristics of the lamina propia?
connective tissue papillae fibroblasts - collagen I and III macrophages and lymphoutes elastin fibres
What are the characteristics of the submucosa ?
loose connective tissue larger blood vessels and nerves fat deposits cheeks, lips and lateral palate acts as a cushion
How long does it take skin to regenerate ?
27 days
How long does it take oral mucosa to regenerate ?
9-14 days
high tissue turonver
What happens in oral mucosa regeneration ?
cells are made in the basal lamina
dividing basal cells
replace cells in the top
self renewal and terminally differentiated cells
What are the layers of the stratified squamous epithelium of the oral mucosa ?
Basal layer- basale
prickle layer - spinosum
granular- granulosom
Keratinised layer- corneum
What is stratum basale ?
cuboidal cells single proliferating layer attached to lamina propia keratin 5 and 14 stem cells
What is stratum spinosum ?
round spiny cells
desmosomes
keratin 1 and 10
cociin and involucrin
What is stratum granulosum ?
larger flatter cells several layers loss of cell organelles cytoplasm with keratohyaline granules profilaggrin
What is stratum corneum ?
very flat cells
filaggrin binds keratin filaments
involucrin networks
cornified envelope
What are the types of keratinisation status ?
parakeratinised
orthokeratinised
non keratinised
What is parakeratinisation ?
cornified cell layer with dead cells
cell nuclei present
gingiva
What is orthokeratinisation ?
dead cells with no nuclei - cornified layer
flat cells
present in specialised tongue mucosa
What is non keratinised ?
superficial layer with live cells in coreneum layer
no kerathyalin molecules
in lining mucosa
What are other cell types in the oral mucosa ?
melanocytes- in basal layer, make melanin and transfter to kaeratinocytes via dendritic processes
merkel cells- basal layer, sensory receptor cells, sense light touch
langerhans cells- suprabasal, dendritic cells - antigen processing
lymphocytes- inflammatory response
What type of mucosa does the hard palate have ?
masticatroy mucosa
What is the incisive papilla ?
prominence overlying the nasopalatine foramen
need to relieve in denture fitting
What is the nasopalatine foramen ?
blood vessels and nerves to supply the hard palate
What is the palatine raphe ?
midline epithelial ridge joined to the bone
What is the palatine rugae ?
unique epithelial folds
What is fovea palatini ?
openign ducts of the minor salivary glands
posterior border of the upper denture
What type of mucosa is present at the border of the alveoalr bone and the lateral hard palate ?
submucosa
What is the keratinisation staus of masticatory mucosa ?
ortho and para
What is the buccal mucosa bounded by ?
upper and lower vestibular fornices
What are fordyces spots ?
ectopic sebaceous glands without hair follicles
produce sebum to lubricate lips
What is the parotid papilla ?
opening of the parotid gland opposite the 2nd maxillary molar
What is the linea alba ?
parakeratinisation at the level of the molar occlusal plane
What type of mucosa is on the floor of the mouth ?
movable
lining mucosa above mylohyoid
What is the lingual frenulum ?
attached to the underside of the tongue to floor of mouth
What is ankyglossia ?
lingual frenulum to short
What is the sublingual papilla ?
opening of the submandibular salivary ducts
What is the sublingual folds ?
opening of the sublingual salivary ducts
What are fimbriated folds ?
remnants of tongue development
What is the histological properties of the labial and buccal mucosa ?
thick epithelium non keratinised
long and slender papilale in the lamina propia
submucosa attached to muscle
motility and stability
What ar the histological properties of the floor of the mouth and tongue ?
thin epithelium non jeratinised
thin short papillae in the lamina propia
thin submucosa
motility
What is the vermillon zone ?
lining mucosa
keratinised
between skin and labial mucosa
What is the labial mucosa ?
a lining mucosa
non keratinised
What is the alveolar mucosa ?
lining mucosa
non keratinised
What is the gingiva ?
masicatory mucosa
para and ortho keratinised
What is the mucogingival junction ?
junction between the alveolar mucosa and the gingiva
What are the fucntions of the tongue ?
swallowing
speech
taste
immune function
What are the parts of the tongue ?
anterior two thirds- palatal part - epeithelium from ectoderm
posterior one third- pharyngeal part- epithelium from endoderm
What are the cicumvallate papillae ?
big
taste
between the anterior 2/3 and posterior 1/3
What are the lingual follicles ?
lymphoid function
What are the foliate papillae ?
slits on the side of the tongue
taster
anterior 2/3
What are the fungiform papillae ?
red mushroom shaped
taste
anterior 2/3
What are the filiform papillae ?
masticatory function
white spots
What is the epithelium of the tongue like ?
thick
orthokeratinised in filiform papillae
non keratinised in taste and interpapilalry regions
What is the lamina propia like in the tongue ?
long papillae
minor salivary glands
Is there a submucosa in the tongue ?
no the lamina propia directly attaches to the tongue
What is the function of the specialised mucosa ?
taste
What is atrophy of oral mucosa ?
smoother and dryer surface loss of epithelial ridges fibrosis decreased cellularity in the lamina propa increased fordyces spots
What are the causes of atrophy of the oral mucosa ?
systemic disease
medication that reduces saliva flow
What are age changes in the tongue ?
epithelial atrophy loss of filiform papillae fissured surface varicoase veins burning sensations
What could lead to age related changes in the tongue ?
nutritional deficiencies
medication
What is black hairy tongue ?
hypertrophy of the filiform papillae
accumulation of food debris and microorganisms
What is geographic tongue ?
bening migratory glossitis
atrophy of filiform papillae
migration of depapilaled white border patches
What is recurrent aphtous stoamtitis ?
recurrent mouth ulcers
genetic and stars in childhood
Which diseaeses can also cause mouth ulcers ?
virus- HPV
Iron and Vit B deficiency
Crohns disease
What is lichen planus ?
autoimmune disease
reticular patches
What is white sponge naevus ?
keratin 13/14 mutation
What is leukoplakia ?
white patches formed by hyperkeratosis
potentially malignant
OPMD
What are risk factors for oral cancer ?
p53 protein mutations
tobacco alcohol HPV
What is the mechanism of oral cancer ?
over expression of protoncogenees inactivation of tumour supressors increased cell proliferation genome instability cell mobility evasion
What are 90% of oral cancers ?
squamous cell carcinoma
What is the progresssion of oral cancer ?
hyperplasia dysplasia carcinoma i situ inasvie carcinoma metastasis
What are the most common pre malignant lesions ?
leukoplakia
eryhtroplakia
What is regenerative medicine ?
aims to develop novel therapies to repair or regenerate tissues and organs that have been damaged by injury, cancer and disease.
What is repair ?
restoration of tissue function but with impaired tissue architecture
What is regeneration ?
complete restoration of tissue architecture and fucntion
Do humans have full regenrative cacpacity ?
no
What is the current function with restoration ?
we are limited to incomplete restoration of original tissue function
What are the 2 routes in regenrative medicine ?
cellular therapy- use exogenous or own progenitro cells
tissue engineering- using biomaterial like collagen
What are stem cells ?
unspecialised cells that can self renew and differentiate into other cell type
development and regeneration
1 is precursor other is self renewal
What are totipotent stem cells ?
can differentiate into all cell types
eg. fertilised egg cell
What are pluropotent stem cells ?
can differentiate into cells of the embryonic germ layers
embryonic stem cells
What are multipotent stem cells ?
can differentiate into many cell types
haemopoietic stem cells
What are oligopotent stem cells ?
can differentiate into a few cell types
myeloid precursors
What are unipotent stem cells ?
can differentiate into 1 cell type
mast cell prescursors
What are quadripotent stem cells ?
can differentiate into 4 cell types mesenchymal cartialge stroma fat
What are the problems with stem cells ?
not fully understood
genetic control is difficult
in niches- hard to find
What are the 4 mechanisms of tissue regeneration ?
stem cell mediated regeneration
epimorphosis
morphollaxis
compensatory regualtion
What is stem cell mediated regernation ?
repalcement of lost tissue by stem cell activity
eg. blood replacement by haemopoietic stem cells
What is epimorphosis ?
dedifferentiation of cells at wound site and formation
of undifferentiated cells
redifferentate to form lost structure
amputation of amphibian limbs
What is morphollaxis ?
depatterning of existing tissue with little or new growth
What is compensatory regulation ?
differentiated cells divide and maintain fucntions
liver regeneration
What are the 4 stages of wound healing in oral mucosa ?
haemostasis
inflammatory response
epithelial response
connective tissue repair
What is haemostasis ?
cessation of blood loss
What happens in haemostasis ?
vascular damage means blood leaks into a wound
clot formation via coagulation, fibrin and platelets
barrier that unites wound margins
protects exposed tissue
What does haemostasis provide ?
provisional scaffold for subsequent colonisation by repairative cells
What happens in the inflammatory response ?
toxins enter triggering the inflammatory response
leakage of plasma proteins by vasodilation
cytokines and GFs released
these stimulate leukocyte migration to the wound - chemotaxis
neutrophils appear and become activated
What do monocytes de in the inflammatory response ?
they become macrophaes
remove debris via phagocytosis
What do lymphocytes do ?
humoral immune system response
What do mast cells do ?
promote inflammation
What happens in the reparative epithelial response ?
mobilisation of cells- widening intercellular spaces
increased basal cell proliferation
epithelial cells adjacent to wound migratte under clot
epithelial sheet formation
reach opposing margin and stop
stratification
What is the reparative connective tissue response ?
fibroblasts proliferate and migrate to connective tissue
deposit collagen in disorganised manner
angiogenesis at wound margin
new ECM - fibronectin, laminin and collagen - scaffold
collagen deposition accelerated - scar tissue formation
What is angiogenesis ?
production of new blood vessels from exiting ones
What is the exception that the oral mucosa can do with scar tissue ?
oral mucosa is able to remodel scar tissue removing it
original collagen formation- looks the same
What are the first fibroblasts that enter the wound site ?
contractile myofibroblasts
What is the origin of contractile myofibroblasts ?
pericytes
What do contractile myofibroblats do ?
form connections with each other and collagen fibrils
draw wound together in contraction
What is the compromise between time and tissue integrity ?
to prevent further damage
quick wound healing but reduced tissue integrity
What leads to immobilisation and rigidity of repair site ?
disorganised collagen
What prevents scar formation is the oral mucosa ?
remodelling of collagen fibres
What is the procedure for wound healing after tooth extraction ?
socket fills with clot
proliferation and migration of epithelial cells
epithelialisation of socket
osteogenic precursor cells migrate to clot
osteoblasts differentiate and bone is deposited
What is the procedure for wound healing at DGJ ?
colonisation of wound by epithelial cells - make a junctional epithelium
ODAm expressed
JE grows downwards
new DGJ
What must happen when restoring the periodontium ?
resotre a unit
cementum , PDL, alveolar bone and gingiva
What do fibroblasts do in periodontal regenration ?
remodel collagen fibres in periodontal regeneration
What do endothelial cells do in periodontal regeration ?
for new blood vessels from exiting blood vessles
angiogenesis
Where do cementoblasts originate from in periodontal regernation ?
epithelial rest cells of malassez
Where do osteoblasts in periodontal regernation originate from ?
mesenchymal progenitor cells
periosteum
Do normal tooth movements require an inflammtroy response ?
no
Why do we need the inflammatory response in infection and repair ?
to combat infection
What does chronic inflammation do ?
inhibits stem cells activation
cell recruitment
proliferation
differentation
What are the molecular approaches to tooth repair ?
FGF
PDGF
TGF-
apply growth factor cocktails to root surfaces
Which enamel matrix protein stimulates repair ?
emdogain
Why cant we regenerate enamel ?
ameloblasts die at the end of development
Which aspects of enamel repair can we control ?
physico chemical properties of remineralisation
calcium
phosphate
fluoride
How are early carious lesions reversible ?
if the surface enamel is intact and acid abcteria are removed
Is dentine living ?
yes
What does the dentine reparative process depend on ?
extent and duration of caries
structural variation - tubules occlude dor not
age of tooth - size of pulp chamber
What happens to dentine with a slow and prolonged insult ?
occlusion of dentine tubules by collagen plug or sclerotic dentine
reactionary dentine formed by existing odontoblasts
What happens to dentine with a rapid and severe insult ?
reactionary dentine possibly if some cells survive
reparative denime fomred by differentiated odontoblast like cells
dentine is less tubular
What does repair of the dentine pulp complex involve ?
inflammation but no epithelial response
What are sources of stem cells for dental regeneration ?
dental pulp
exfoliated primary teeth
from PDL
What are tissue engineering regenerative methods ?
biodegradable scaffolds
cell seeding
implants with bioactive surface for regenration
What is the pattern of cementum relating to age ?
young- more acellular cementum- less mechanical exposure
old- occlusal wear, induces cellular cementum in apical and interradicular areas
What is the clinical significance of enamel and cementum not meeting at the CEJ ?
root dentine is exposed
lead to dentine sensitivity
10% cases
What is the keratinisation status of the gingival epithelium ?
para and ortho
masticatory function
What is the keratinisation status of the sulucular epithelium ?
non keratinised
What are the components of nasmyths membrane ?
epithelial tag
primary enamel cuticle and REE remnants
How does the junctional epithelium attach to enamel ?
hemidesmosomes and IBL
Why is there no bleeding when a tooth erupts ?
epithelial continuity as REE and oral epithelium fuse
What happens to the surface cells of the junctional epithelium ?
they are sloughed off and enter the GCF
What is the appearance of the cells in the deepest aprt if the JE ?
JE similar to REE
How can we identify inflammation histologically ?
dark blue staining
inflammatory cells- neutrophils, monocytes and lymphocytes
What effect does inflammation have on the sulcular epithelium ?
sulcular epithelium moves downwards and form long processes - project into lamina propia
What happens to the basal lamina when inflammed ?
more penetrable for microbes and toxins
What is the function of keratin in mucosa ?
resist abrasion and masticatory mucosa
What are the tissues that comprise the submucosa ?
adipose tissue
larger vessels and nerves
loose connective tissue
minor salivary glands
What is the significance of inter digitation of epithelial and connective tissue interface ?
inter digitation of epithelial ridges increases surface area and increases stability
Which collagen is predominant in gigniva and hard palate ?
strong fibres that provide tensile strength and resist shearing forces
What is the physiological response of the periodontal tissues after application of a light orthodontic response ?
metabolic response
Which type of bone forms the cortical plate of the alveoalr bone ?
bundle bone
What is the size of the orthodontic force applied to achieve movements of the teeth ?
100-150g
Which nerve endings are evenly distributed in the PDL and serving pain and pressure ?
free ending tree like
What is the aim of guided regeneration of the gingiva ?
prevention of undesirable wound healing
Which structure is not involved in taste ?
foliate papilla
What is the function of the REE ?
forms the DGJ
Which type of collagen is present in the PDL after tooth eruption ?
collagen XII
What are the 2 types of tooth movement ?
natural
forced
What is the pathway of force transmission in a tooth?
crown
cementum
PDL
bone
What is the origin of osteoblasts ?
undifferenetiated mesenchymal cells
What is the origin of osteoclasts ?
blood monocytes
What are the origins of osteocytes ?
osteoblasts
What do the undifferentiated mesenchymal cells in the PDL differentiate into ?
osteoblasts
fibroblasts
What happens when a force of 1 second is applied to teeth ?
PDL doesnt have time to become compressed
alveolar bone gives way
creates piezzoelectirc signal
What is a piezoelectric signal ?
mechanical force to a crystaline structure which creates a movement of electrons - short current
What happens to teeth with a longer force of 1-2 seconds ?
PDL fluid expressed
tooth moves in socket
What happens to teeth with a force of 3-5 seconds ?
PDL fluid redistributed
tissues compressed leading to pain
What happens to teeth with long term orthodontic forces ?
tooth movement in the socket
bony changes occur
What causes bony changes with long orthodontic forces ?
piezoelectric effect
streaming potential
What is the streaming potential ?
longer forces leading to movement of ground substance
potential difference leading to cell permeability
What is the pressure tension theory ?
causes bony changes in long duration
when the PDL has a force applied - one side is compressed and one side is tension
What happens when then PDL is stretched ?
blood flow increased
tension is made
What happens when the PDL is squashed ?
blood flow decreased
pressure is made
What can squashing bone lead to ?
hyalinisation
microfractures
What is the cellular response and systemic response in long term force ?
cellular response- prostaglandins, IL1
systemic response- PTH, vitamin D and calcitonin
What is the effect of the force on teeth dependent on ?
size and duration of force
What does applying a force to a tooth do ?
force transmitted through PDL and bone
biological electricity and pressure-tension theory leading to changes in blood flow
Which areas are osteoblasts recruited in ?
areas of tension- increased bone flow
Which areas are osteoclasts recruited in ?
areas of pressure - decreased bone flow
What happens in the heavy forces ?
blood vessels on squashed side are occluded within seconds
blood flow cut off to the compressed PDL- minutes
cell death in compressed layer
adjacent bone forms hyaline layer
cells beneath the hyaline layer are differentiated into osteoclasts
undermining resorption removes lamina dura
What happens in heavy forces to allow tooth movement ?
undermining resorption
What happens in light forces ?
blood vessels on the pressure side are partially occluded
dilated on the tension side
leads to an alteration in blood flow on the pressure side
allows metabolic changes to occur
cell differentiation in PDL - osteoclasts for pressure side and osteoblasts for tension side
What causes tooth movement in light forces ?
tooth remodelling
What are the 5 types of tooth movements ?
tipping extrusion intrusion translation rotation
What is tipping ?
simple movement
around centre of resistance= third distance from the apex
forces are greatest further away from the apex
100-150 g
What is rotation ?
tipping can be due to excessive compression of PDL
50-100 g
What is translation ?
bodily movement though bone
PDL uniformly loaded
100-150 g
What is extrusion ?
produces tension in PDL fibres
too much can loose vitality
50-100 g
What is intrusion ?
forces concentrated on the root apex
excess damage leads to cementum damage - osteoclasts get access to dentine
root resorption
15-25
What are the adverse effects of orthodontic appliances on roots ?
root resorption - 1-2 mm of root length increased in dilacerated roots thin roots excess force tooth can be made mobile - accelerated in periodontal disease
What are the effects of orthodontic appliances on bone ?
loose about 0.5-1 mm of alveolar crest
What are the adverse effects of orthodontics on PDL ?
maintenance of excessive force leads to damage
important in relapse
What is the response of pulp to orthodontics ?
transient inflammatory response
What is infraocclusion ?
tooth below the occlusal plane
What is the aetiology of infra occlusion ?
ankylosis
What is ankylosis ?
tooth fused to the bone
How does ankylosis occur ?
PDL lost- link between tooth and bone made
What are the causes of ankylosis ?
trauma
Why is their a risk of decalcification with orthodontics ?
poor PH
Why do teeth erupt ?
to maintain contact in occlusion
Why does class II div 2 have a deep overbite ?
lower incisors have nothing to erupt agaisnt
What can retained primary teeth cause with opposite teeth ?
over eruption of opposite
What can overuption lead to ?
gingival trauma
occlusal problems
What is mesial drift ?
natural tendency of teeth to drift forward
When does mesial drift happen ?
early loss of primary teeth
if E lost early 6 will move into space and prevent 5 from erupting
How can we stop mesial drift ?
hold the space
How can mesial drift be useful ?
loose 6 early
7 drifts into space
What is late lower incisor crowding ?
old age
pressure from 8s
What is ageing ?
progressive decline in the ability to respond effectively to stresses of the environment
Why do teeth discolour with age ?
thinning of the enamel
thickening of the dentine- shines through translucent enamel
How do teeth become stained ?
stains and food particles become trapped in microscopic pores that are remineralised - trapped
What are strains visible as microscopically ?
dark areas under the surface
more prominent striae of retzius
How do whitening agents work ?
produce oxygen free radicals from hydrogen peroxide which penetrates enamel and reduces larger molecules into smaller molecules
smaller molecules can diffuse out the pores
What is the action of fluoride ?
fluoride replaces hydroxide groups in hydroxyapatite
leads to a more mineralised fluorapatite
Why are old people more resistant to caries ?
fluorapatite is harder than hydroxyapatite
What is the first step in caries ?
chalk white early white lesion
Are white spot lesions always due to caries ?
no can be developmental if they are shiny
Are White spot lesions reversible and if so how ?
they are reversible if the enamel is intact and the biofilm removed
Does secondary or primary dentine form faster ?
primary forms faster
What happens to the pulp chamber in age ?
size of the pulp chamber reduces
root canals very narrow
What are secondary dentine tubules like ?
they are continuous with primary dentine tubules
less secondary tubules
show a change in direction between primary and secondary
leads to contour line of owen
Where does peritubular dentine begin to form ?
on the outter dentine where the stresses are felt the most
What happens to form peritubular dentine ?
precipitation of calcium phosphate ions
Is peritubular dentine hypo or hyper mineralised ?
hypermineralised - 90%
What are the characteristics of peritubular dentine ?
doesnt contain collagen
tubule is completely occluded - sclerotic dentine made
What is sclerotic dentine ?
complete occlusion of dentinal tubules by peritubular dentine
leads to dentine becoming transparent
What are the 2 methods of sclerotic dentine formation ?
physiological - ageing- seen in the roots
pathological - in response to caries- between carious lesion and the pulp
What is reactionary dentine ?
slow response - slow attrition
existing odontoblasts lining the pulp make reactionary dentine
inferior quality of dentine - less tubules
What is repairative dentine ?
quick rapid response
odontoblast like cells (recruited from the pulp) make repairative dentine as original odontoblasts cells have been killed by the stimulus
repairative dentine has less tubules and is less mineralised
What does natural attrition of the crown stimulate ?
peritubular dentine
dentine is less sensitive and less permeable
What happens to compensate for tissue loss in attrition ?
reactionary dentine
What does repairative dentine form in response to ?
strong stimulus- caries
What do dead tracts form in response to ?
attrition and caries
repairative dentine forms to seal off the pulp from microorganisms
empty dentine tubules as odontoblast processes (dead) retract
dark appearance
What are age changes in the pulp ?
less cells
narrow pulp chamber
calcified stones
What are the types of calcified structures that form in the pulp ?
false pulp stones
true pulp stones
diffuse calcifications
What are false pulp stones ?
not made by odontoblasts
concentric layers of calcified tissue
degenerated pulp tissue in pulp
What are true pulp stones ?
denticles
contain organic tissue and dentinal tubules
made by odontoblasts
What are diffuse calcifications ?
blood vessels associated with collagen fibres
become calcified as the blood vessels are calcified
What happens to cementum with age ?
increases in thickness
not known of the pattern if thickness
When is cellular cementum formed ?
in response to attrition it forms at the apex to lift the tooth up
What are the age changes in the PDL ?
decreased cell numbers
fibroblasts have shorter lifespans , diminished collagen synthesis and degradation activity
thicker bundles
irregular organisation of sharpeys fibres
less remofelling of PDL- older teeth are less mobile
What are the age changes the oral mucosa ?
thinning of tongue epithelium
reduced taste sensation
increased susceptibility to cancerous lesions
What happens to the alveolar bone when there is a loss of teeth ?
alveoalr bone receeds
What are the age changes to the salivary glands ?
decrease in the amount of salivary glands
increase in fibrotic tissue
xerostomia- medication use
What is physiological attrition ?
mastication and contact with food
affects interproximal and occlusal surfaces
reactionary dentine forms in response
block off dentine tubules and leads to dead tracts
What is pathological attrition ?
chewing - habitual and abnormal
bruxism
flat occlusal plane
dentine exposed- hypersensitivity
What is abrasion ?
tooth wear comes into contact with foreign objects
pipe smoking
abrasive toothpastes and brushing
What is erosion ?
progressive loss of hard tissues due to chemical dissolution
acid of non bacterial origin
extrinsic- diet
intrinsic- acid reflux / bulimia
Why doesnt enamel dissolve at ph7 ?
pH7 the saliva is super saturated
enamel wont dissolve the calcium phosphate
What happens below pH6 to enamel ?
saliva is unsaturated
pulls out ions
acidic dissolution initiates erosion
What is the development process for a lesion ?
subsurface translucent zone
development of a dark zone
typical zoned structure of early white spot lesion
cavitation and spread along EDJ
How can we arreest non cavitated lesions ?
removal of plaque
seal and hold
What is secondary dentine ?
normal continuation of dentine after root development
odontoblasts lining the pulp
reduce the size of the pulp chamber and root canals
found on the roof and floor of the pulp chamber
What is reactionary dentine ?
in response to mild stimuli like attrition
odontoblast cells lining the pulo
irregular structure with few tubules
What is repairative dentine ?
in response to strong stimuli
original odontoblasts killed so need to use odontoblast like cells
What is the progression of pulpal pain ?
dentine hypersensitivity reversible pulpits irreversible pulpitis apical periodontitis peri apical abscess
What is dentine hypersensitivity ?
short sharp pain arising from exposed dentine in response to stimuli
What are the stimuli that can trigger dentine hypersensitivity ?
thermal evaporative tactile osmotic chemical
How can be dentin ebe exposed ?
by gingival recession or lack of enamel
What are the causes of pulpal inflamIs tehre amation ?
caries
defective restorations
trauma
dens invaginations - infolding of enamel into the dentine
Is there always a correlation of inflamed pulp and pain ?
no- an inflamed pulp can be painless
What is reversible pulpitis ?
short pain in duration
pain disappears when stimulus removed
poorly localised
How can we manage reversible pulpitis ?
remove irritant and restore
What is irreversible pulpitis ?
pain longer in duration
pain PERSISTS when stimulus removed
spontaneous
How can we manage irreversible pulpitis ?
pulpotemy
pulpectomy
extraction
NOT ANTIBIOTICS
What is symptomatic apical periodontitis ?
pain
apical inflammation
still respond to nerve tests
What is asymptomatic chronicl apical periodontitis ?
no TTP
no response to nerve tests
no pain
apical radiolucency
What is apical acute abscess ?
non responsive
swelling
febrile
What is a chronic apical abscess ?
draining sinus
asymptomatic
