Arrangement of the dental tissues (OB1) Flashcards
(23 cards)
1
Q
cervical margin
A
margin between crown and root
2
Q
apex
A
point of root
3
Q
anatomical crown
A
- full crown dimensions
- part of tooth covered with enamel
4
Q
clinical crown
A
-part of tooth visible in mouth clinically
5
Q
erupting teeth
A
clinical crown
6
Q
gingival recession
A
- clinical crown > anatomical crown
- gum receeds back, revealing more of root
- occurs with old age/disease
7
Q
enamel
A
- covers anatomical crown
- outer surface like veneer
- epithelial product
- 96% inorganic (hydroxyapatite)
- 2mm thick max
- translucent
- non-vital
- hard (KHN 360-390)
- brittle
- made up of enamel prisms
8
Q
amelodentinal junction
A
junction between enamel and dentine
9
Q
dentine (and pre-dentine)
A
- main bulk of hard tissue of tooth
- underneath enamel
- specialized (mineralised) connective tissue
- hard (KHN 75)
- strong and resilient
- 70% mineral and 20% collagen (matrix)
- > when initially formed = pre-dentine which is non mineralised and located beside pulp
- collagen fibres run parallel to the amelodentinal joint
- dentine is highly tubular (tubules are continuous with pulp)
- > there are 15,000-65,000 tubules per mm squared
- dentine is described as a vital tissue as it is alive and can respond as it contains nerves and tissues
10
Q
cementum
A
- thin layer of hard tissue covering root
- mineralised tissue
- mineralised specialized connective tissue
- covers tooth roots
- tooth support
- resistant to resorption (movement)
- > close to fibres and around the tooth ‘locking it in’
- > force changes shape of bone however cementum remains in tact therefore orthodontics = small changes over long time
11
Q
pulp
A
- within cementum
- specialized connective tissue
- essentially a matured dental papilla
- dentine is the calcified tissue of the pulp
- pulp functions:
- > dentine formation
- > defence and repair
- > sensory
- as pulp is effectively enclosed in a rigid chamber (dentine), there is no scope for tissue to swell when inflamed
- > packed full of nerves (contains the most pain producing nerves in the body)
12
Q
ideal properties of tooth
A
- strong
- hard
- wear resistant (abrasive diet)
- resistant to chemical damage (acidic foods)
- ability to respond to insult/damage
- ability to repair itself to damage
- aesthetic
13
Q
chemical components of enamel
A
- 96% mineral (calcium phosphate and hydroxyl groups/hydroxiyappetite - the hard part)
- 1-2% matrix (organic component)
- 2% water
14
Q
chemical components of dentine
A
- 70% mineral (calcium phosphate and hydroxyl groups/hydroxiyappetite - the hard part)
- 20% matrix (organic component)
- 10% water
15
Q
chemical components of cementum
A
- 65% mineral (calcium phosphate and hydroxyl groups/hydroxiyappetite - the hard part)
- 23% matrix (organic component)
- 12% water
16
Q
chemical components of bone
A
- 60% mineral (calcium phosphate and hydroxyl groups/hydroxiyappetite - the hard part)
- 25% matrix (organic component)
- 15% water
17
Q
methods of cutting through enamel
A
- enamel bur (drill) needs to be able to cut through enamel
- > high speed air turbine with either diamond or tungston carbide
- unsupported enamel is easily fractured with a hand instrument eg. chisel (due to the enamel prisms, can fracture along a prism due to how brittle the enamel is)
18
Q
methods of cutting dentine
A
- carious dentine = soft therefore cut with a bladed bur or hand excavator
- sound dentine = less hard than enamel, there are two options for cutting sound dentine -> high speed diamond burs or low/high speed bladed bur
19
Q
dentinal tubules
A
- dentine is highly tubular
- the tubules are continuous with the pulp
- tubules may contain:
- > cell processes
- > nerves
- > fluid (which flows out)
- there are between 15,000-65,000 tubules per mm squared:
- > between 15,000-20,000 per mm squared at the amelodentinal junction (where tubule diameter = 0.5-1 microns, tubule distance apart = 15 microns, 4% of the surface is occupied by tubules)
- > between 45-000-65,000 tubules per mm squared at the predentine (where tubule diameter = 2-3microns, tubule distance apart = 6 microns and 28% of the surface in this area is occupied by tubules)
20
Q
how do fillings stay in (methods of securing fillings)
A
- mechanical (undercut), this method is destructive
- ‘bond’ed to enamel by utilizing the structure of enamel by acid etch (which roughens the tooth)
- ‘bond’ed to dentine by one of three methods:
- > acid demineralisation (dissolves hydroxiappatite, acid permeates in and locks around the fibres)
- > infiltrate collagen with resin
- > penetrate tubules with resin
21
Q
gross anatomy of pulp
A
- pulp horns within the crown
- coronal pulp chamber (chamber between the radicular pulp in coronal section)
- radicular pulp (within the root)
- apical foramen (at apex/point of root/roots, pulp exits tooth at apical foramen/base of the tooth)
- lateral canal (comes off radicular pulp)
- > radicular pulp is treated by draining through pulp chamber then carrying out root canal treatment
- > lateral canals cannot be filled
- > if pulp dies off: treated by filling the space/sealing the space or getting rid of the space by tooth extraction
22
Q
dentine-pulp complex
A
- dentine and pulp are linked embryo-logically, physically and functionally
- dentine is porous therefore any material/procedure may irritate pulp, causing inflammation, however some materials are therapeutic eg. Ca(OH)2
- > dentine is considered vital as it can respond to insult to protect the pulp
23
Q
cementum-enamel relationships
A
- in 60% of cases, cementum overlaps the enamel
- in 30% of cases, cementum meets with enamel
- in 10% of cases, there is a gap between the cementum and enamel, exposing the dentine, causing sensitive teeth as the tubules are exposed (sensitive teeth = shooting pain from stimuli eg. hot/cold, sugary food, drinks)
