BAMS revision Flashcards
what is the periodontium?
tissues surrounding and supporting the teeth
what is the role of the periodontium?
- retain the tooth in the socker
- resist masticatory loads
- defensive barrier (protecting tissues against threats from the oral environment)
junctional epithelium
the physical barrier separating the body tissues from the oral environment
where is the only breach in epithelial attachment?
where the tooth passes through the epithelium
cementum
- covers root dentine
- similar in structure to bone (collagen matrix, lamellar arrangement)
what are the 2 types of cementum?
- cellular
- acellular
cellular cementum
contains no cells, usually adjacent to dentine, no attached fibres
acellular cementum
contains cementocytes, present in apical part of root and in furcation regions, collagen fibres from PDL (sharpey’s)
where is the weakest point of tooth attachment?
apex and furcation regions
what forms the inner lining of the tooth socket?
cortical plate
layer of compact bond that overlies the spongiosa of the alveolar process on the mandible and maxilla
what penetrates the alveolar bone?
nutrient canals (volkmans)
what is the inner bone of the alveolar bone like?
cancellous
contains marrow
what happens to the alveolar bone when teeth are lost?
the bone is resorbed
leaving a residual ridge
what are alveolar canals filled with?
blood vessels
what is in the connective tissue of periodontal ligament?
fibroblasts ECM fibres nerves blood vessels
what is in the PDL matrix?
hyaluronate GAGs
glycoproteins = fibronectin
proteoglycans
behaves like a viscoelastic gel
what are the cells in the PDL?
- fibroblasts
- cementoblasts
- osteoclasts and cementoclasts
- epithelial cells (cell rests or debris of
malassez) - defence cells
how are cysts formed?
lining of cysts created by debris of malassez
epithelial balloon filled with highly protein liquid
what 3 types of sensory nerve are in periodontium?
- mechanoreceptors (A beta and A delta)
- nociceptors (A delta and C)
- autonomic (sympathetic)
mechanoreceptors in periodontium role
- rapidly or slowly adapting
- proprioception; chewing control
A beta and A delta fibres
nociceptors in periodontium role
- protective reflexes
- inhibit jaw elevator motor neurons (popcorn)
A delta and C fibres
autonomic (sympathetic) nerves in periodontium role
blood vessel control - vasocontriction
blood supply of the periodontium
- From inferior & superior alveolar arteries, passing into PDL from alveolar bone
- From lingual & palatine arteries supplying gingivae
true periodontal ligament
fibres connecting tooth to bone at or apical to the alveolar crest
‘gingival’ ligament periodontal fibres
Fibres mainly above the alveolar crest, including ‘free gingival’ fibres
purpose of PDL
- Attaches tooth to jaw
- Transmits biting forces to alveolar bone
Organised connective tissue
Width approx = 0.2 mm
fibres in PDL
Collagen = (types I & III)
- Principal fibres - true periodontal ligament
- Support tooth; load bearing
Oxytalan fibres
- Function uncertain
alveolodental fibre types (5)
- Alveolar crest
- Horizontal
- Oblique
- Apical
- Interradicular (multi rooted teeth)
interdental fibres
- Transseptal fibres
- between the cementum of two proximal teeth
- Interdental septum = part of alveolar bone between two teeth
gingival fibre groups
- Dento-gingival
- Alveologingival
- Dento-periosteal
- Circular
gingival fibre groups role
support the free gingiva
present in the lamina propria in marginal gingivae
‘gingival margin’
where the gingiva meets the tooth
muco-gingival margin
where the ginigiva meets the mucosa
junctional epithelium type
stratified non-keratinising epithelium
junctional epithelium special properties
2 basal laminas
- One faces tooth (internal)
- One faces connective tissue (external)
how does the junctional epithelium and epithelia attach?
- Internal basal lamina & hemidesmosomes
Connects the junctional epithelium to tooth surface
interdental epithelium type
stratified squamous (keratinised)
what type of forces are PDL mainly subjected to?
intrusive forces and rarely extrusive and horizontal forces
cells in dental pulp
- Odontoblasts
- Fibroblasts
- Defence cells
extracellular components of dental pulp
Fibres
- Collagen
- Oxytalan
Matrix
- Proteoglycans
- Chondroitin SO4
- Dermatan SO4
nerves in dental pulp
- Sensory
- Autonomic (sympathetic)
what makes up the dental pulp?
- cells
- exracellular components
- nerves
- blood vessels
- lymphatics
what is in the cell rich zone?
fibroblasts
functions of dental pulp
- Nutritive - blood vessels
- Dentine growth (primary + secondary)
- Dentine repair (tertiary)
- Defence (immune cells; lymphatics)
- Neural (sensory - pain… control of dentinogenesis)
what does both the dentin and pulp develop from?
dental papilla
structural links between the dentine and pulp
Pulpal elements extend into dentine
- Odontoblast processes
- Nerve terminals
- Immune cells (dendritic cells)
- Dentinal fluid
NB** no blood vessels in normal dentine
primary dentine
rapid formation
from ADJ –> till full tooth formed
secondary dentine
slower
continues to be made and laid down throughout life
reason why pulp shrinks over lifetime
haemodynamics and hydrodynamics of pulp
Fluid leaks from pulp capillaries - interstitial space
- Some drain by lymphatics
- Some pass along dentine tubules (dentinal fluid)
reactionary dentine
- in response to mild stimulus
- laid down by primary odontoblasts
secreted by original odontoblasts
reparative dentine
- in response to intense stimulus that destroys primary odontoblasts
formed by odontoblast-like cells (secondary odontoblasts)
abarsion due to
mastication
attrition due to
bruxism
abfraction due to
occlusal overload (fractions and cervical lesions)
erosion due to
diet, gastric reflux, vomitting
what does the odontoblast layer act as?
permeability barrier
- Separates pulp and tubular space
- Regulates movement of material between pulp and tubular extracellular fluid
- Movement may be in either direction
what moves from the pulp to the dentine?
- nutrients to sustain the cell
- formation of 2 + 3 dentine
- function of tubular nerves (e.g. K+)
what moves from dentine to pulp?
- medicaments applied to dentine
- diffusion of toxins, from bacteria, components of filling materials
anatomy of pulp nerves
Branches of the alveolar nerves
Neurovascular bundles enter pulp via apical foramen and pass along root canal in centre of pulp towards the coronal pulp chamber
- Branches fan out in subodontoblastic layer; some nerves enter dentinal tubules
innervation of dentine
some nerves enter tubules
- Under cusps : 40% of tubules contain nerve
- Some axons extend 100-200um
Tubular innervation is less in coronal dentine (15%) and root dentine (4%)
- Few axons enter tubles; most end in pulp-predentine region
what stimuli can bypass the hydrodynamic mechanism?
act directly on intradental nerves
- intense heating
- intense cooling
- electrical current
- pain-producing chemicals
how can high fillings cause dentine pain?
force distorts the dentine and alters the tubular fluid flow
intradental nerves are…
A beta and delta (large and small myelinated)
C fibres (unmyelinated)
What activates A beta and A delta fibres in intradental nerves?
hydrodynamic stimuli applied to dentine
probably mediate ‘normal’ dentinal sensitivity
What activates C fibres in intradental nerves?
directly by stimulu, rather than hydrodynamic mechanism
- respond to most forms of intense stimulation
probably mediate pain associated with pulp inflamttion (e.g. caries)
4 things that control pulpal blood flow
Local factors e.g. metabolites
Nerves
- Sympathetic
- Somatic afferents
Circulating hormones e.g. adrenaline
Drugs
- E.g. local anaesthetic preparations with vasoconstrictors
5 functions of pulp nerves
Sensory - mediating pain
Control of pulp blood vessels
- Sympathetic : vasoconstrictor
- Afferents : vasodilator (axon reflex)
Promote neurogenic inflammation
Neuropeptides : subset P, CGRP
Promote dentine formation
dentine-pulp first response to injury
immediate, nociceptor activation (pain)
dentine-pulp response to injury after 1 min.
- early inflammatory response
- kinins, prostaglandins, neuropeptides
- vasodilatioin
dentine-pulp response to injury after 10 mins
- nociceptor sensitisation
- extravasation of fluid, odema
- polymorph migration
dentine-pulp response to injury after 100mins
- enzyme activation; nerve growth factor
- monocyte presence
dentine-pulp response to injury after 1 day
- nerve spouting (NGF)
- increased axonal transport
- altered excitability of CNS synapses
dentine-pulp response to injury after 1 week
- repair tertiary dentine formation
pulpitis
Acute inflammation in the pulp
- Pulp cannot swell as it is confined within the pulp chamber
Odema causes increase in pulp pressure
- Can have variable effects on blood flow + nerve excitability
what enamel is more mineralised and harder?
surface enamel is more mineralised and harder than deeper enamel
how does enamel hardness decrease
decrease in hardness from cusp tip to cervical margin
mineral structure varies too
what is a basic unit of enamel?
rod/prism
enamel rods run
from ADJ to surface
enamel rod dimensions
5um x 2.5mm
long parallel enamel rods are due to
daily growth (approx. 4um)
cross sections in rods
brown transverse stiae are due to
weekly intervals
25-35um apart
does rod orientation effect demineralisation?
yes
distinction in head and tail regions is cause by variations in orientations of HA in different parts of the rod
HA content in enamel
95% weight
90% volume
Water content in enamel
4% weight
5-10% volume
organic matrix content in enamel
1% weight
(1-2% volume)
Proteins : amelogenins; enamelins; peptides; amino acids
what does the organic compound of enamel regulate?
the nanomechanical properties of enamel = FLEXIBILITY
how are crystallites deposited?
at right angles to the ameloblast membrane
where are HA crystallites largest?
in enamel, compared to dentine, cementum and bone
ground section of tooth shows
mineral present
no soft tissues
decalcified sections of tooth shows
no mineral
just soft tissues
how to enamel rods run?
in a sinusoidal course
what causes banding patterns (Hunter-Schreger bands) in enamel?
periodic orientation
hunter-shreger bands
- Rod periodic orientation
- Absent in outer enamel
gnarled enamel can be found at
cusps
incremental lines in enamel are
brown striae of retzius
enamel tufts at the ADJ are
hypomineralised regions due to residual matrix protein prism boundaries
enamel lamella at ADJ are
incomplete maturation of groups of prims
- fault line extending through enamel thickness
enamel spindles at ADJ are
odontoblast processes extending into the enamel
