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DMS :( > endo materials > Flashcards

endo materials Flashcards

1
Q

endo materials

A 
instruments
irrigants
intra-canal medicaments
obturation materials
sealers
pulp capping materials
root end filling materials
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2
Q

functions of instruments

A

remove hard and soft tissues
removes MOs
creates space for disinfectants/medicaments
creates appropriate shape for disinfection

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3
Q

stress

A

deforming force measured across a given area
tensile/compressive/shear/torsional
stress = F/A

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4
Q

stress concentration point

A

abrupt changes in the geometric shape of a file that leads to a higher stress at that point

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5
Q

strain

A

response of a material to stress
amount of deformation a file undergoes
change in length/length

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6
Q

elastic deformation

A

reversible deformation that does not exceed elastic limit

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7
Q

elastic limit

A

a set value representing the maximal strain that when applied to a file allows the file to return to original dimensions

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8
Q

shape memory

A

alloys - can be deformed at one temp but when heated/cooled return to their original shape
= behave differently in the canal as they do outside

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9
Q

plastic deformation

A

permanent bond displacement occurring when plastic limit exceeded

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10
Q

plastic limit

A

the point at which a plastic deformed file breaks

- instrument separation - can affect outcome but not always

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11
Q

cyclic fatigue

A 
freely rotating - not bound
in curved canals
generation of tension/compression cycles - compression on one side tension on the other
failure
e.g. MB canal of molar
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12
Q

why might an instrument that breaks due to cyclic fatigue be easier to remove?

A

freely moving

torsional bound so may be more difficult

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13
Q

torsional fatigue

A

when bound in canal
instrument binds in RC, is further rotated - stress in torsion, torque
structure of metal will undergo changes - reversible or irreversible - depends on amount of rotation when instrument binding

elastic phase - elastic limit - plastic phase - fracture

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14
Q

elastic phase

A

no irreversible changes

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15
Q

plastic phase

A

irreversible changes in structure of metal

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16
Q

in reciprocation how should the clockwise and anticlockwise angles of rotation be set?

A

lower than the elastic limit
safer procedure the lower the angles of rotation
as long as can still cut dentine, advance apically in the canal and remove the cutting debris in a coronal direction

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17
Q

preventing instrument fracture

A

training
create a manual glide path
crown-down instrumentation technique to ensure straight line access
electric speed and torque controlled motor
NiTi files - constant motion using gentle pressure
avoid triggering or disable the autoreverse mode
avoid rotary files in abruptly curved or dilacerated canals

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18
Q

classification of instruments

A 
manually operated
low-speed instruments e.g. GG
engine-driven NiTi rotary instruments 
engine-driven instruments that adapt to canal shape
engine-driven reciprocating instruments
US instruments
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19
Q

SS components

A

alloy - Fe, C, Cr

Ni maybe

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20
Q

improved carbon steel

A

rusting = all single use now

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21
Q

Cr in SS

A

13-26%
prevents rusting
passivation layer or chromium oxide

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22
Q

SS instrument manufacture

A 
cut then twist
 - machined SS wire
 - square/triangular
 - twisted
 - work-hardening
cut
 - machine SS wire into desired shape
 - work-hardening
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23
Q

work hardening

A

strengthening of a metal by plastic deformation
crystal structure dislocation
dislocations interact and create obstructions in crystal lattice
resistance to dislocation formation develops
observed work hardening

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24
Q

what can work hardening lead to?

A

cyclic fatigue

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25
Q

Nitinol

A

equiatomic alloy of Ni and Ti
exotic metal - does not conform to typical rules of metttalurgy
superelasticity - application of stress does not result in usual proportional strain

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26
Q

NiTi crystal lattice structures

A

temp dependent structures martensite and austenite

crystal lattice structure altered by temp or stress

character and proportions determine mechanical properties of metal

martensite form - soft, ductile and easily deformed

austenitic form - quite strong and hard

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27
Q

taper

A

diameter change along working surface

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28
Q

flute

A

groove to collect dentine and ST

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29
Q

leading/cutting edge

A

forms and deflects dentine chips

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30
Q

land

A

surface extending between flutes = can be flat, grooved or concave
affects how it behaves in canal

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31
Q

relief

A

reduction in surface of land

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32
Q

helix angle

A

angle cutting axis forms with long axis of file

33
Q

constant helix angle

A

can behave like a screw (bad)

34
Q

modify helix angle

A

can’t behave like a screw

35
Q

positive rake angle

A

provides the active cutting action of the K3

36
Q

wide radial land

A

provides blade support while adding peripheral strength to resist torsional and rotary stresses

37
Q

radial land relief§

A

reduces friction on the canal wall

38
Q

third radial land

A

stabilises and keeps the instrument centred in the canal and minimised ‘over engagement’

39
Q

irrigant ideal properties

A 
facilitate removal of debris
lubrication
dissolution of organic and inorganic matter
penetration to canal periphery 
kill bacteria/yeasts/viruses
biofilm disruption
biological compatibility
does not weaken tooth structure
40
Q

NaOCl conc

A

3%

41
Q

NaOCl chemistry

A

ionises in water into Na+ and OCl-
establishes equilibrium with hypochlorous ion HOCl

acid/neutral HOCl predominates
pH 9 and above OCl- predominates
HOCl is responsible for antibacterial activity

42
Q

NaOCl properties

A

effect on organic material
inability to remove smear layer by itself
possible effect on dentine properties

43
Q

factors important for NaOCl function

A 
concentration
volume 
contact
mechanical agitation - MDI
exchange
44
Q

smear layer

A

formed during prep
organic pulpal material and inorganic dentinal debris
superficial 1-5um with packing into tubules
bacteria contamination, substrate and interferes with disinfection
prevents sealer penetration

45
Q

removal of smear layer options

A

17% EDTA
10% citric acid
MTAD (mixture of a tetracycline isomer, an acid and a detergent)
sonic and US irrigation

46
Q

NaOCl and CHX interaction

A

forms parachloroaniline
cytotoxic and carcinogenic
uncertain bioavailability

47
Q

irrigant selection

A

NaOCl and EDTA shouldn’t be present in root canal at same time
order they should be used debate

48
Q

sodium hypochlorite (parcan)

A

3%
dissolves organic material, bacteriocidal
disinfection
30ml per canal, continual irrigation time for at least 10mins following completion of prep and prior to obturation

49
Q

EDTA usage

A

17%
smear layer removal
penultimate rinse for 1min
3ml per canal

50
Q

Chlorhexidine digluconate (Corsodyl)

A

0.2%

check dam integrity/disinfect tooth surface

51
Q

Chlorhexidine digluconate (GlucoChex)

A

2%
antimicrobial
suspect iatrogenic damage
only use if NaOCl contraindicated

52
Q

sterile saline (Baxter)

A

wash out canal is NaOCl accident suspected

53
Q

properties of an ideal obturation material

A 
easily manipulated with ample working time
dimensionally by tissue fluids stable
seals the canal apically and laterally
non-irritant
impervious to moisture
unaffected by tissue fluids
inhibits bacterial growth
radiopaque
does not discolour tooth
sterile
easily removed if necessary
54
Q

GP production

A

produced from juice of trees of the sapodilla family

trans isomer of polyisoprene

55
Q

GP a and B forms

A

exists in 2 crystalline forms a and B
a phase is the naturally occurring form
a phase heated above 65 degrees melts into amorphous phase
cooled slowly returns to a phase
cooled rapidly recrystallises as B phase
B phase used in commercially prepared dental GP

56
Q

GP constituents

A

GP 20%
zinc oxide 65%
radio pacifiers 10%
plasticisers 5%

57
Q

types of GP cones

A

standardised
non-standardised
size matches

58
Q

what should be done to GP cones before obturation?

A

put in NaOCl as not sterile when packaged

59
Q

modified GP

A

can impregnate with bio ceramics and antimicrobials

- enhance bonding between GP and sealer

60
Q

sealer functions

A

seals space between dentinal wall and core
fills voids and irregularities in canal, lateral canals and in between GP points used in lateral condensation
lubricates during obturation

61
Q

properties if an ideal sealer

A 
exhibits tackiness to provide good adhesion
exhibits a hermetic seal (air tight)
radiopacity
easily mixed
no shrinkage on setting
non-staining
bacteriostatic or does not encourage growth 
slow set
insoluble in tissue fluids
tissue tolerant
soluble on re-tx
62
Q

zinc oxide and eugenol chemistry

A

mixing vehicle mostly Eugenol
finely sifted ZnO to enhance flow
can be modified with germicides
rosin or canada balsam to increase dentine adhesion
corticosteroids
setting - chemical and physical embedding of ZnO in matrix of Zn eugenolate
eugenolate formation - hardening
- CaOH accelerates so must be removed from canals
free eugenol which remains can act as an irritant

63
Q

zinc oxide and eugenol properties

A

less radiopaque than GP
ZnO antimicrobial - may be cytoprotective
resin acids 90% of rosins affect lipids in cell membrane therefore strongly antimicrobial/cytotoxic
although toxic may overall be beneficial with long lasting antimicrobial and cytoprotective effects
lose vol with time due to dissolution - resins can modify this
- problem - lose vol - eventually washed away

64
Q

GI sealers

A

advocated due to dentine bonding properties
removal upon re-tx is difficult
minimal antimicrobial activity
little clinical data to support use

65
Q

resin sealers e.g. AHPlus, AH26

A 
epoxy resin
paste-paste mixing
slow setting 8hrs
good sealing ability
good flow
not really bioactive
initial toxicity declining after 24hrs
radiopaque
biocompatible
dimensionally stable
66
Q

epiphany

A

dual cure dental resin composite sealer - used with Resilon

requires self-etch primer

67
Q

EndoRez

A 
UDMA resin-based sealer
hydrophillic
good penetration into tubules
biocompatible 
good radiopacity
68
Q

calcium silicate sealers

A 
high pH12.8 during initial 24hrs of setting
hydrophillic
enhanced biocompatibility
dimensionally stable
non-resorbable
excellent sealing ability
quick set 3-4hrs - requires moisture
easy to use
osteo and bioinductive - stimulates a response in the body
69
Q

medicated sealers

A

sealers containing paraformaldehyde not acceptable
lead and mercury components removed
cytotoxic and carcinogenic
severe and permanent effects (toxic) on PR tissues

70
Q

pulp capping/root end filling material uses

A 
pulp cap
pulpotomy and pulp regeneration
lateral perforation repair
apicoectomy
apexification
root resorption repair
furcation perforation repair
71
Q

grey MTA

A

earliest formulations
less toxic than Portland cement
better setting characteristics
tooth discolouration

tricalcium silicate, dicalcium silicate, tricalcium aluminate, tetracalcium aluminoferrite, bismuth oxide

72
Q

white MTA

A

smaller particle size
reduced discolouration
one that is typically used now
tricalcium silicate, dicalcium silicate, calcium aluminate, bismuth oxide, calcium sulphate dehydrated

73
Q

what is MTA based on?

A

cement

74
Q

MTA setting reaction

A

hydraulic cements composed of several phases
hydration - mixed with H2O - chemical reaction
white and grey diff setting reactions
mixing, dormancy, hardening
modifications to change characteristics
extended setting times

75
Q

bio ceramic cements

A

shorter setting times
tissue response
- no areas of fibrosis/chronic inflammation
- just see induction of cementogenesis etc

76
Q

the ideal root filling?

A

generally a core material and sealer

always sealer used to create a fluid-tight seal

77
Q

now shift to a sealer-based obturation

A

single point obturation with excess of sealer - still need a GP cone to get apical control

78
Q

CaOH properties

A

bacteriocidal and bacteriostatic properties
high pH
adheres directly to dentine
thin so won’t reduce strength of restorative material
won’t dissolve in biological liquids

79
Q

CaOH high pH

A

stimulates fibroblasts for reparative dentine formation - stimulates decalcification of demineralised dentine by stimulating pulpal cells
neutralises low pH from acidic restorative materials

DMS :( (18 decks)

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