Arrangement of the dental tissues (OB1) Flashcards Preview

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Flashcards in Arrangement of the dental tissues (OB1) Deck (23):
1

cervical margin

margin between crown and root

2

apex

point of root

3

anatomical crown

-full crown dimensions
-part of tooth covered with enamel

4

clinical crown

-part of tooth visible in mouth clinically

5

erupting teeth

clinical crown

6

gingival recession

-clinical crown > anatomical crown
-gum receeds back, revealing more of root
-occurs with old age/disease

7

enamel

-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

amelodentinal junction

junction between enamel and dentine

9

dentine (and pre-dentine)

-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

cementum

-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

pulp

-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

ideal properties of tooth

-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

chemical components of enamel

-96% mineral (calcium phosphate and hydroxyl groups/hydroxiyappetite - the hard part)
-1-2% matrix (organic component)
-2% water

14

chemical components of dentine

-70% mineral (calcium phosphate and hydroxyl groups/hydroxiyappetite - the hard part)
-20% matrix (organic component)
-10% water

15

chemical components of cementum

-65% mineral (calcium phosphate and hydroxyl groups/hydroxiyappetite - the hard part)
-23% matrix (organic component)
-12% water

16

chemical components of bone

-60% mineral (calcium phosphate and hydroxyl groups/hydroxiyappetite - the hard part)
-25% matrix (organic component)
-15% water

17

methods of cutting through enamel

-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

methods of cutting dentine

-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

dentinal tubules

-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

how do fillings stay in (methods of securing fillings)

-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

gross anatomy of pulp

-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

dentine-pulp complex

-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

cementum-enamel relationships

-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)