periodontium Flashcards
what is periodontium
tissue surrounding and supporting teeth
what is the role of the periodontium
- retains tooth in the socket
- resists masticatory loads
- is a defensive barrier, protecting tissues against threats from the oral environment
what is junctional epithelium
the physical barrier separating the body tissues from the oral environment
*protects against microorganisms - every drop of saliva has 10^6 micro-organisms
what is the epithelial attachment
what you are trying to make healthy
what is the difference between gingival disease and periodontal disease
difference is established by the space between the gingiva and the tooth - sulcus/pocket
- periodontal disease is commonly pockets beyond 3mm
- periodontal disease common in older patients
what is cementum
- covers root dentine
- anchor for periodontal fibres
- similar in structure to bone - has collagen matrix and lamellar arrangement like lamellar bone
what are the 2 types of cementum
- cellular - has cementocytes and cells have projections
* acellular - no cells or very few cells
what is cementum laid down by
cementocytes
what are the characteristics of acellular cementum
- no or few cells within
- usually adjacent to dentine
- first formed (primary cementum)
- also called EXTRINSIC FIBRE CEMENTUM
- has collagen fibres from the periodontal ligament - these are called Sharpay’s fibres
- present on cervical 2/3 of root
- is acellular because there is no need for metabolic activity
what are the characteristics of cellular cementum
- contains cementocytes
- later formed (secondary cementum)
- present on apical part of root and in furcation regions
- no Sharpay’s fibres - when treating furcations the restorations are more likely to fail as less fibres
- also called INTRINSIC FIBRE CEMENTUM
- intrinsic collagen fibres run parallel to the surface
- has no role in tooth attachment
- may represent a transitional form
how does the type of cementum affect the treatment
depends whether cellular or acellular cementum - treatment will vary
*can sometimes get areas where the two types overlap each other
does cementum help overcome toothwear
Yes.
Cementum helps overcome toothwear which is overcome by eruption so need cementum in these areas
what does alveolar bone do
- provides attachment for periodontal ligament fibres
- very important for transferring forces across bone as it would break without cushioning
- supports the teeth
what is the structure of alveolar bone
- similar to bone elsewhere in the body
- ‘cortical plate’ forms inner lining of tooth socket
- penetrated by nutrient canals - VOLKMANNS canals
- has inner ‘cancellous’ bone (spongy), containing marrow
- inferior of tooth socket may have nutrient foramina perforating the inner cortical bone - corresponds to lamina dura in radiographs
what happens when teeth are lost
the alveolar process is resorbed, leaving a residua ridge
how wide is periodontal ligament
approximately 0.2 mm
what is periodontal ligament
an organised, regular connective tissue
what makes up PDL
- cells
- extracellular matrix (ground substance)
- fibres - run in specific direction, attach tooth to jaw
- nerves
- blood vessels
what is the structure and function of the matrix
- contains hyaluronate GAGs (glycosaminoglycans)
- glycoproteins - fibronectin
- proteoglycans - proteodermatin sulphate and chondroitin/dermatan
- behaves like a viscoelastic gel - wobbles like a jelly so allows it to spring back to original shape
what is the structure and function of the cells
- fibroblasts - generate and maintain the structure
- cementoblasts - same job as fibroblasts
- osteoclasts and cementoclasts - destroy/resorb bone and cementum
- epithelial cells - originate in the root, called cell rests (or debris) of Malassez - important in pathological implications such as cysts
- defence cells - important in periodontal disease - link to the autoimmune response
what nerves are there in the periodontal ligament
sensory and autonomic (sympathetic)
what is the sensory nerves responsible for
- mechanoreceptors (A delta and A beta fibres)
- can be rapidly or slowly adapting
- control chewing through proprioception - automatically changes the way you eat different thing - can be problem with dentures as no PDL
- nociceptors (A delta and C fibres)
- protective reflexes
- inhibit jaw elevator motor neurons
- A fibres are myelinated, C fibres are not
what are the autonomic nerves responsible for
*blood vessel control - vasoconstriction
why do we need to have adrenaline in LA
for vasoconstriction - need to constrict to reduce the clearance of LA from area so procedure can be longer
*but with PDL, don’t want reduced blood flow so need to do some procedures without adrenaline
