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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
Nitinol
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
26
NiTi crystal lattice structures
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
27
taper
diameter change along working surface
28
flute
groove to collect dentine and ST
29
leading/cutting edge
forms and deflects dentine chips
30
land
surface extending between flutes = can be flat, grooved or concave affects how it behaves in canal
31
relief
reduction in surface of land
32
helix angle
angle cutting axis forms with long axis of file
33
constant helix angle
can behave like a screw (bad)
34
modify helix angle
can't behave like a screw
35
positive rake angle
provides the active cutting action of the K3
36
wide radial land
provides blade support while adding peripheral strength to resist torsional and rotary stresses
37
radial land relief§
reduces friction on the canal wall
38
third radial land
stabilises and keeps the instrument centred in the canal and minimised 'over engagement'
39
irrigant ideal properties
``` 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
NaOCl conc
3%
41
NaOCl chemistry
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
NaOCl properties
effect on organic material inability to remove smear layer by itself possible effect on dentine properties
43
factors important for NaOCl function
``` concentration volume contact mechanical agitation - MDI exchange ```
44
smear layer
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
removal of smear layer options
17% EDTA 10% citric acid MTAD (mixture of a tetracycline isomer, an acid and a detergent) sonic and US irrigation
46
NaOCl and CHX interaction
forms parachloroaniline cytotoxic and carcinogenic uncertain bioavailability
47
irrigant selection
NaOCl and EDTA shouldn't be present in root canal at same time order they should be used debate
48
sodium hypochlorite (parcan)
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
EDTA usage
17% smear layer removal penultimate rinse for 1min 3ml per canal
50
Chlorhexidine digluconate (Corsodyl)
0.2% | check dam integrity/disinfect tooth surface
51
Chlorhexidine digluconate (GlucoChex)
2% antimicrobial suspect iatrogenic damage only use if NaOCl contraindicated
52
sterile saline (Baxter)
wash out canal is NaOCl accident suspected
53
properties of an ideal obturation material
``` 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
GP production
produced from juice of trees of the sapodilla family | trans isomer of polyisoprene
55
GP a and B forms
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
GP constituents
GP 20% zinc oxide 65% radio pacifiers 10% plasticisers 5%
57
types of GP cones
standardised non-standardised size matches
58
what should be done to GP cones before obturation?
put in NaOCl as not sterile when packaged
59
modified GP
can impregnate with bio ceramics and antimicrobials | - enhance bonding between GP and sealer
60
sealer functions
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
properties if an ideal sealer
``` 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
zinc oxide and eugenol chemistry
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
zinc oxide and eugenol properties
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
GI sealers
advocated due to dentine bonding properties removal upon re-tx is difficult minimal antimicrobial activity little clinical data to support use
65
resin sealers e.g. AHPlus, AH26
``` 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
epiphany
dual cure dental resin composite sealer - used with Resilon | requires self-etch primer
67
EndoRez
``` UDMA resin-based sealer hydrophillic good penetration into tubules biocompatible good radiopacity ```
68
calcium silicate sealers
``` 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
medicated sealers
sealers containing paraformaldehyde not acceptable lead and mercury components removed cytotoxic and carcinogenic severe and permanent effects (toxic) on PR tissues
70
pulp capping/root end filling material uses
``` pulp cap pulpotomy and pulp regeneration lateral perforation repair apicoectomy apexification root resorption repair furcation perforation repair ```
71
grey MTA
earliest formulations less toxic than Portland cement better setting characteristics tooth discolouration tricalcium silicate, dicalcium silicate, tricalcium aluminate, tetracalcium aluminoferrite, bismuth oxide
72
white MTA
smaller particle size reduced discolouration one that is typically used now tricalcium silicate, dicalcium silicate, calcium aluminate, bismuth oxide, calcium sulphate dehydrated
73
what is MTA based on?
cement
74
MTA setting reaction
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
bio ceramic cements
shorter setting times tissue response - no areas of fibrosis/chronic inflammation - just see induction of cementogenesis etc
76
the ideal root filling?
generally a core material and sealer | always sealer used to create a fluid-tight seal
77
now shift to a sealer-based obturation
single point obturation with excess of sealer - still need a GP cone to get apical control
78
CaOH properties
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
CaOH high pH
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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