W11

Question 1

what are the key histological features of enamel

Answer 1

hardest substance in the body
highly mineralised
acellular
96% inorganic (hydroxyapatite - calcium and phosphate rod formation)
3% organic - proteins cover crystals in delicate lattice, influencing chemical behaviour of enamel
1% water in space between crystals

Question 2

what are enamel prisms

Answer 2

tightly packed separated by intercrystalline spaces or pores (microporons) - a net flow of fluid out of enamel prisms

Question 3

are enamel hydroxyapatite crystals pure

Answer 3

no as they contain other ions (fluoride, carbohydrate and sodium)
carbohydrate makes them more susceptible to dissolving

Question 4

what is the histological features of dentin

Answer 4

70% mineral and acellular (hydroxyapatite)
30% organic water cologen and mucopolysacharide)

Question 5

describe the demin/remin process

Answer 5

Demin- in prensence of acid phosphate ions will be combined with hydrogen ions producing hydrogen phosphate= unable for crystal formation, PH supersaturated solution is lowered to just saturated due to loss of minerals= critical ph appears (5.5) - if we go beyond that point- inbalance and loss of ions into solution and binding with hydrogen and being lost

Remin - reversal - fluoride brings up ph - fluoropatite crystals

Question 6

when does a cavitation form

Answer 6

first intial white spot lesion - ICDAS
if the demineralisation and remin imbalance continue - the surface of the incipient lesion collapses, so the structure of the enamel becomes extremely weak leading to cavitation icdas 3

Question 7

what does ICDAS stand for

Answer 7

international caries detection and assessment system

Question 8

why can dental caries be classified as a phasic disease process

Answer 8

there is supersaturation, saturation and undersaturation

Question 9

what are the chemical reactions during the caries process

Answer 9

when exposed to sugars, acids and carbohydtrates the ph goes down to 5.5 and Hydroxyapatite is reactive with hydrogen ions
if it stays at this level - phosphate ions bind to hydrogen ions - hydrogen phosphate = DEMINERALISATION

Question 10

would a new tooth or old tooth have higher concentration of flouro-hydroxyapatite?

Answer 10

one that has been in the mouth for some time
it requires the demineralisation and remineralisation process to allow flouride to be incorporated into the crystal (need cariogenic challenges or acidic challenges for flouride to be incorporated)

Question 11

What is the critical PH for hydroxyapatite

Answer 11

5.5

Question 12

What is the critical PH for fluoro-hydroxyapatite

Answer 12

4.5

Question 13

What is the critical PH for Dentin

Answer 13

6.3

Question 14

What is the critical PH for Cementum

Answer 14

6.7

Question 15

what are the key zones of incipient enamel lesions

Answer 15

surface zone
Body of lesion
Dark Zone
Translucent zone

Question 16

which zone has the largest pores

Answer 16

Body of lesion

Question 17

what are the key zones of a cavitated dentinal lesion

Answer 17

zone of destruction
zone of penetration
demineralised dentine

Question 18

what zones of a cavitated dentinal lesion get kept during the cavity prep stage

Answer 18

demineralised dentine - keep and remineralise (firm affected dentine)

Question 19

what are the soft dentin zones of a cavitated dentinal lesion and what do you do with them

Answer 19

zone of destruction
zone of penetration
Destroy/get rid of them

Question 20

under what circumstances can caries be arrested and remineralised

Answer 20

must have favourable environment in the mouth
improve oral hygeine

Question 21

why is the pulp chamber in a molar in a 40year old likely to be smaller than one in a 10year old

Answer 21

pulp chambers decrease in size as you age
tubular serosis and the formation of new dentin are the pulps responses to destructive processes - it works to slow down the advancemennt of the lesion

dead tracts occur when odontoblasts die without tubular sclerosis - new odontoblasts can still be formed

CONTINUED DEPOSITS OF SECONDARY DENTIN INTO THE PULP CHAMBER

Question 22

how does root caries occur

Answer 22

cementum exposed due to recession or perio treatment - higher critical ph of 6.7
does not have that layer of enamel that is highly mineralised and less soluble
will see quite early and easily - easy to arrest and remineralise

Question 23

what is recurrent caries

Answer 23

occurs at margins of restorations

Question 24

what is residual caries

Answer 24

infected or demineralised dentin is left in cavities during cavity prep

Question 25

how can radiographs tell the difference between recurrent and residual caries

Answer 25

residual = radiolucent area under recently placed restoration

Question 26

what are the characteristics of soft dentin

Answer 26

INFECTED DENTIN
- high levels of bacteria
- complete demineralisation
- complete or partial collapse of the tubule structure
- loss of dentin sensitivity

Question 27

what are the characteristics of firm dentin

Answer 27

AFFECTED DENTIN
- there is enough mineral content to maintain tubular structure
- there are minimal levels of bacteria
- as long as there is 10% of the organic level of mineralisation, remin can occur

Question 28

What are the 7 steps in dentine destruction

Answer 28

Sclerotic dentin (white streaks)
Zone of demineralisation (gets bigger)
Odontoblasts lay down secondary dentine
Pointed cavitation (allows bacteria to go through enamel)
Cavitation gets bigger
As biofilm comes into contact with dentine one of destruction forms
Masses of bacteria and destruction of dentin (all need to be removed)