Periodontium Flashcards
what is periodontium?
tissues surrounding and supporting the teeth
functions of periodontium? (3)
- retain tooth in socket
- resist masticatory loads (resist and relieve, transfer pressure onto periodontium bone)
- defensive barrier, protecting tissues against threats from oral environment
how much micro bacteria in each drop of saliva?
10^6
what do we aim to treat in periodontal disease?
junctional epithelium
what is unique about junctional epithelium?
it is a physical barrier that is the only breach in the body’s surface
(where teeth pass through the oral epithelium)
- separates the body tissues from oral environment
2 divisions of periodontal disease
- diseases of the gingiva alone
- diseases of all periodontal tissues
gingival periodontal disease identified by….
no pocket present
periodontal tissue disease identified by….
pockets (more than 3.5mm)
what is a sulcus?
a pocket
where is cementum?
covers root dentine
what is cementum structure like? (2)
very similar in structure to bone
- lamellar arrangement compared to radial arrangement of bone
collagen matrix
difference between cementum and bone structure
cementum is lamellar arrangement whereas bone is radial arrangement in general
- cementum is always linear
function of cementum
provides attachment for some periodontal fibres
- anchor for periodontal fibres
2 types of cementum
cellular cementum
acellular cementum
what lays down cementum?
cementocytes
acellular cementum characteristics
no cells within
usually adjacent to dentine
first formed (primary cementum)
cellular cementum
contains cementocytes
later formed (secondary cementum)
present in apical part of root and in furcation regions
why do we need to know where the different types of cementum are?
When doing root scaling different response in different regions due to different cementum types
alternative classification for acellular cementum
acellular extrinsic fibre cementum
alternative classification for cellular cementum
cellular intrinsic fibre cementum
acellular extrinsic fibre cementum characteristics (3)
- collagen fibres from PDL (Sharpey’s fibres)
- equivalent to primary acellular cementum
- present on cervical 2/3 of roots
cellular intrinsic fibre cementum characteristics (5)
- no Sharpey’s fibres
- intrinsic collagen fibres parallel to surface (run alongside)
- equivalent to secondary cellular cementum
- no role in tooth attachment
- may represent a transitional form
why do furcation regions and apex of roots need newly formed cellular cementum?
Furcation and apex of roots needs newly formed cementum needed to overcome tooth wear - counteracted by slight tooth eruption so cementum created at apex
why does acellular cementum provide?
anchorage of teeth
why is periodontal treatment less successful in furcation and apical areas?
as less Sharpey’s fibres are present
what forms the inner lining of tooth socket?
‘cortical plate’
what are functions of alveolar bone?
suports the teeth
provides attachment for periodontal ligament fibres (‘Sharpey’s fibres’)
- transfer of forces from teeth to bone, needs cushion to prevent bone damage as bone softer than teeth
why is there a need for periodontium?
to transfer of forces from teeth to bone, needs cushion to prevent bone damage as bone softer than teeth
what penetrates alveolar bone?
nutrient canals
- Volkmann’s canals
what is the inner bone of alveolar bone like?
inner ‘cancellous’ bone, containing marrow
what happens to the alveolar bone when teeth are lost?
alveolar process is resorbed, leaving a ‘residual ridge’
what 5 things are in periodontal ligament?
- cells
- extracellular matrix
- fibres (collagen, Sharpey’s fibres)
- nerves
- blood vessels
What are the 3 things in the periodontal ligament matrix (ground substance)?
- hyaluronate GAGs
- Glycoproteins (fibronectin)
- proteoglycans (proteodermatan sulphate, chondroitin/dermantan SO4 hybrid)
what glycoprotein is in PDL ground substance?
fibronectin
what proteoglycans are in the PDL ground sunstance?
proteodermatan sulphate
chondroitin/dermantan SO4 hybrid
properties of the PDL ground substance
viscoelastic gel
- like glue/jelly due to proteins infrastructure
- capacity to regain shape, bounce back
what can periodontal disease cause to happen to the PDL ground substance?
loss of viscoelastic gel property
bacteria relationship with PDL ground substance?
become specialised to aggregate around chemicals in PDL ground substance - use as a way of living
what type of bacteria harbour in PDL ground substance?
anaerobic or facultative (do not need O2)
- use proteins for energy (not glucose), hinder viscoelasticity
5 types of cells in PDL
fibroblasts cementoblasts osteoclasts and cementoclasts epithelial cells defence cells
fibroblasts role in PDL
needed to create and maintain infrastructure
cementoblasts role in PDL
need to create cementum
osteoclasts and cementoclasts role in PDL
break down - reorganise and destroy bone
epithelial cells role in PDL
cell rests (or debris) of Malassez - important, many functions including in pathological situations e.g. cysts
importance of cell rests (or debris) of Malassez in PDL
have many functions including in pathological situations e.g. cysts
defence cells role in PDL
PDL has a link to autoimmune diseases - body destroying itself
2 classes of nerves in PDL
sensory - mechanoreceptors and nociceptors
autonomic (sensory)
sensory nerve types in PDL
mechanoreceptors (A beta and A delta fibres)
nociceptors (A delta and C fibres)
mechanoreceptors in PDL role
rapidly or slowly adapting
proprioception; chewing control (different forces and resistance applied to hard Vs soft foods)
nociceptors in PDL role (4)
- protective reflexes - recognise harm (jaw jerk reflex)
- inhibit jaw elevator motor neurons
- autonomic (sympathetic)
- blood vessel control - vasoconstriction
importance of PDL in relation to denture work
can have different ‘taste’ due to difference in mastication process
- no PDL in denture - lose ability to recognise food and harm as no nerves (mechano/nociceptors)
autonomic (sympathetic) blood vessel control in PDL role
Blood vessel control is a way of removing LA from area
- So reduce clearance of LA from area when vasoconstrict so less LA needed for longer period of anaesthesia
Problem as reduced blood flow
- not wanted in some cases,
- here non vasoconstrictors LA used to maintain blood flow
ID block tries to block LA to core nerves
2 PDL blood supplies
from inferior and superior alveolar arteries
- passing into PDL from alveolar bone
from lingual and palatine arteries
- supplying gingivae
what is true periodontal ligament?
fibres connecting tooth to bone or apical to alveolar crest
what is gingival ligament?
fibres mainly above the alveolar crest, including ‘free gingival’ fibres
arranged in a way to create infrastructure for gingival attached to bone or tooth or bone and tooth
2 functions of periodontal ligament
attaches tooth to jaw
transmits biting forces to alveolar bone (from tooth to bone)
2 physical characteristics of periodontal ligament
organised (regular) connective tissue
width of PDL is approx. 0.2mm - variable
3 fibre types potentially in PDL
collagen (types I and III)
oxytalan fibres
(elastic fibres)
role of collagen fibres in PDL
principal fibres - true periodontal ligament
support tooth; load bearing
diseases can affect specific types of collagen
(types I and III in PDL)
role of oxytalan fibres in PDL
present in humans but no clear repsonse so function is uncertain
role of elastic fibres in PDL
absent in human PDL
but used in animal research testing
2 main principal PDL fibre groups
alveolo-dental ligament
interdental ligament
5 types of alveolo-dental ligament
- aleveolar crest
- horrizontal
- oblique
- apical
- interradicular
alveolar crest ligament location and role
parallel upwards slant to crest
stretch when tooth goes upwards
function more bearing than energy
horizontal ligament location and role
rotational activity
below alveolar crest ligament
oblique ligament location and role
transfer force from tooth to bone
downwards slant from bone to tooth in mid root area
apical ligament location and role
coil like receiving force
apex of tooth root
interradicular ligament role
only in multi-rooted teeth
interdental ligament type
transseptal fibres
trasnseptal fibres role
connects tooth to tooth - important as not connected to bone
role of gingival fibre groups
support free gingivae
- not connecting bone to tooth (but each separately
where is gingival fibre groups present?
in lamina propria in marginal gingiva
4 types of gingival fibre groups
dento-gingival
alveolo-gingival
dento-periosteal
circular
what does dento-gingival fibres connect?
tooth to gingiva
what does alveolo-gingiva fibres connect?
bone to gingiva
what does dento-periosteal fibres connect?
tooth to periosteum
what does circular fibres do?
around the tooth
creates a supportive structure for gingiva
- important in gingival disease
3 gingiva classes
free gingiva
attached gingiva
alveolar mucosa
what separates the 3 gingiva classes
border lines
free gingival groove
mucogingival line
sulcular epithelium
epithelium that is covering the gingival surface
apically bounded by the junctional epithelium and meets the epithelium of the oral cavity at the height of the free gingival margin
- nonkeratinised
junctional epithelium role
connects epithelium to enamel
specail arrangement of junctional epithelium
hemidesosomes on one side
basal layers on both sides
- creates appropriate environment for enamel connection
regeneration of junctional epithelium
throughout the lost space, thus reducing the loss of epithelium attachment
junctional epithelium is elongated - tissue regeneration to treat
what is the Interdental Col?
area between 2 teeth that are protected by contact points
specialisation of interdental col
epithelium is non keratinised
because no loading forces of mastication
what is the PDL response to loading?
PDL is mostly subjected to intrusive forces
- mastication
- swallowing
- speech
- parafunction (e.g. clenching, grinding)
teeth are rarely subjected to extrusive and horizontal forces
- sticky foods, orthodontic forces
what forces are mainly put on teeth?
intrusive
- mastication
- swallowing
- speech
- parafunction (e.g. clenching, grinding)
what forces are rarely put on teeth?
teeth are rarely subjected to extrusive and horizontal forces
- sticky foods, orthodontic forces
what do loads applied to tooth do?
push the tooth into the socket
steps in tooth and PDL loading
- initial elastic component
- later, viscous ‘creep’ - due to viscoelastic properties
- tension in PDL fibres
- compression of ECF
