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BDS3 DMS > Endodontic Materials > Flashcards

Endodontic Materials Flashcards

1
Q

7 endodontic material categories

A
  • Instruments
  • Irrigants
  • Intra-canal medicaments
  • Obturation materials
  • Sealers
  • Pulp Capping materials
  • Root-end filling materials
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2
Q

5 endodontic instruments uses

A
  • Mechanical phase of chemomechanical disinfection
  • Metal files used to remove soft and hard tissues
  • Removes micro-organisms
  • Creates spaces for disinfectants/medicaments
  • Creates appropriate shape for obturation
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3
Q

8 key physical properties

A
  • Stress
  • Stress concentration point
  • Strain
  • Elastic limit
  • Elastic deformation
  • Shape memory
  • Plastic deformation
  • Plastic limit
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4
Q

stress

A

deforming force measured across a given area

tensil/compressive/shear/torsional

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5
Q

stress concentration point

A

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

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6
Q

strain

A

response of a material to stress

anount of deformation a file undergoes

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7
Q

elastic limit

A

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

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8
Q

elastic deformation

A

reversible deformation that does not excess elastic limit

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9
Q

shape memory

A

shape memory alloys are materials that can be deformed at one temperature but when heated or cooled, return to their original shape

e.g. robut file that fills up root canal when heated

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10
Q

plastic deformation

A

permanent bond displacement occurring when elastic limit exceeded

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11
Q

plastic limit

A

the point at which a plastic deformed file breaks

leads to instrument separation

  • clinical failure
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12
Q

cylic fatigue

A

freely rotating in a curvature

generation of tension/compression cycles

cyclic fatiugue = failure

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13
Q

torsional fatigue

A

bind to dentinal wall

rotate but not bond portion

  • plastic deformation between 2 parts = failure
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14
Q

7 prevention methods for endodontic instrument failure

A
  • Training and proficiency in the NiTi system of choice
  • Create a manual glide path
  • Employ a crown-down instrumentation technique to ensure straight-line access
  • Use an electric speed and torque controlled motor
  • NiTi files should be used in constant motion using gentle pressure
  • Avoid triggering or disable the autoreverse mode
  • Use of rotary files in abruptly curved or dilacerated canals should be avoided
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15
Q

6 classifications of endodontic instruments

A
  • Manually operated (ISO No. 3630-1)
  • Low-speed instruments
  • Engine-driven nickel-titanium rotary instruments
  • Engine-driven instruments that adapt to canal shape
  • Engine-driven reciprocating instruments
  • Ultrasonic instruments
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16
Q

stainless steel

A

alloy of iron, carbon and chromium

nickel may also be present

  • improved carbon steel - rusting
    • 13-36% chromium prevents rusting
    • passivation layer of chromium oxide
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17
Q

2 manufacturing techniques of stainless steel endo instruments

A
  • Machined stainless steel wire
  • Cut into Square/Triangular or Twisted
    • Work-hardening occurs – improves

or

  • Machine stainless steel wire into desired shapes
    • Work hardening
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18
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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19
Q

nitinol

A

Equiatomic alloy of nickel and titanium

Exotic metal

  • does not conform to typical rules of mettalurgy

Super-elasticity

  • application of stress does not result in usual proportional strain
    • Behaves slightly different
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20
Q

NiTi Crystal Structure

A
  • Temperature-dependent structures martensite and austenite
  • Crystal lattice structure altered by temperature or stress
  • Character and proportions determine mechanical properties of the metal
  • Martensite form, it is soft and ductile and easily deformed
  • Austenitic form is quite strong and hard
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21
Q

6 components of endodontic rotary instruments

A
  • taper
  • flute
  • leading/cutting edge
  • land
  • relief
  • helix angle
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22
Q

taper

A

diameter change along working surface

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23
Q

flute

A

groove to collect dentine and soft tissue

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24
Q

leading/cutting edge

A

forms and deflects dentine chips

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25
Q

land

A

surface extending between flutes

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26
Q

relief

A

reduction in surface of land

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27
Q

helix angle

A

angle cutting axis forms with long axis of file

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28
Q

impact of subtle difference in endodontic instrument features

A

large change in characteristics of instrument

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29
Q

positive helix/rake angle provides

A

active cutting surface action of the K3

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30
Q

third radial land role

A

stabilises and keep the instrument centred in the canal and minimises ‘over-engagement’

31
Q

wide radial land provides

A

blade support while adding peripheral strength so resist torsional and rotary stresses

32
Q

radial land relief

A

reduces friction on the canal wall

33
Q

properties of irrigants key to role

A

central role in endodontic treatment

  • 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
34
Q

formula for sodium hypochlorite

A

NaOCl

35
Q

NaOCl irrigant reaction

A

NaOCl ionises in water into NA+ and the hypochlorite ion, OCl-

Establishes equilibrium with hypochlorous acid (HOCl)

  • Acid/Neutral HOCl predominates
  • pH 9 and above OCl- predominates

HOCl is responsible for antibacterial activity

36
Q

what component of NaOCl is responsible for antibacterial activity

A

HOCl

37
Q

3 negatives of NaOCl

A
  • Effect on organic material
  • Inability to remove smear layer by itself
  • Possible effect on dentine properties
38
Q

5 factors key to NaOCl function

A
  • concentration
  • volume
  • contact
  • mechanical agitation
  • exchange
39
Q

preparation of the canal for obturation

A
  • Smear layer formed during preparation
  • Organic pulpal material and inorganic dentinal debris
  • Superficial 1-5µm with packing into tubules
  • Bacterial contamination, substrate and interferes with disinfection
  • Prevents sealer penetration
40
Q

4 ways to remove smear layer

A
  • 17% EDTA
  • 10% Citric Acid
  • MTAD (Mixture of a Tetracycline isomer, an Acid, and a Detergent
  • Sonic and Ultrasonic irrigation

Watch apical control!

41
Q

5 things used during canal irrigation

A
  • sodium hypochlorite
  • EDTA
  • chlorhexidine digluconate
  • sterile saline

NaOCl and EDTA not present at same time in canal as EDTA effects NaOCl therapeutic benefits

42
Q

sodium hypochlorite as irrigant

A

trade: parcan

3%

  • dissolve organic material
  • bactercidal

recommended for disinfection

30ml per cnal

continual irrigation for at leat 10 mins following complerion of prep prior to obturation

43
Q

EDTA as irrigant

A

17%

  • smear layer removal

3ml penultimate rinse for 1 min

44
Q

corodyl as irrigant

A

chlorhexidine digluconate 0.2%

used for checking dam integrity and disinfect tooth surface

45
Q

gluco-chex as irrigant

A

chlorhexidine digluconate 2%

  • antimicrobial

use when suspect iatrogenic damage

  • but only when NaOCl contraindicated
46
Q

sterile saline in irrigation

A

used to wash out canal

suspect hypochlorite accident

volume as required

47
Q

irrigant interaction

A

Interaction with NaOCl forms para-chloroaniline

  • Cytotoxic and carcinogenic
  • Uncertain bioavailability
48
Q

11 properties for ideal obturation materials

A
  • Easily manipulated with ample working time
  • Dimensionally by tissue fluids stable
  • Seals the canal laterally and apically
  • Non-irritatant
  • Impervious to moisture
  • Unaffected by tissue fluids
  • Inhibits bacterial growth
  • Radiopaque
  • Does not discolour tooth
  • Sterile
  • Easily removed if necessary
49
Q

Gutta percha

history

A
  • Most common core material
  • One of oldest dental material in use today
    • Produced from juice of trees of the sapodilla family
  • Natural rubber and gutta percha are polymers of same monomer - isoprene
    • Trans isomer of polyisoprene
  • Exists in two crystalline forms alpha and beta
    • Alpha phase is the naturally occurring form
      • Alpha phase heated above 65°C melts into amorphous phase
        • Cooled slowly returns to alpha phase
        • Cooled rapidly recrystalises as beta phase
    • Beta phase used in commercially prepared dental gutta-percha
50
Q

gutta percha cones

components

A
  • 20% Gutta-percha
  • 65% Zinc Oxide
  • 10% Radiopacifiers
  • 5% Plasticizers

Standardised, non-standardised and size-matched

51
Q

3 sealer functions

A
  • Seals space between dentinal wall and core
  • Fills voids and irregularities in canal, lateral canals and between gutta-percha points used in lateral condensation
  • Lubricates during obturation
52
Q

11 properties of ideal sealer

A
  • Exhibits tackiness to provide good adhesion
  • Establishes a hermetic seal
  • 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 retreatment
53
Q

zinc oxide and eugenol

sealer

properties

A
  • Mixing vehicle mostly eugenol
  • Finely sifted zinc oxide to enhance flow
  • Radio-opacity < gutta-percha
  • Can be modified with germicides
  • Rosin or Canada Balsam to increased dentine adhesion
  • Corticosteroids
  • Zinc Oxide effective antimicrobial and may afford cytoprotection
54
Q

Zinc oxide as antimicrobial and cytoprotective functions

A
  • Resin acids 90% component of Rosins affect lipids in cell membrane thus strongly antimicrobial/cytotoxic
  • Although toxic, may overall be beneficial with longlasting antimicrobial effect combined with cytoprotective effects
55
Q

zinc oxide and eugenol

setting

issues

A
  • Setting is a chemical process combined with physical embedding of zinc oxide in a matrix of zinc eugenolate
    • Eugenolate formation constitutes hardening – CaOH accelerates this process so must be removed from canals
  • Free eugenol which remains can act as an irritant
  • Lose volume with time due to dissolution (apical seal diminished)
    • resins can modify this
56
Q

Glass ionomer sealers

A
  • Advocated due to dentine bonding properties
  • Removal upon retreatment is difficult
  • Minimal antimicrobial activity
  • Little clinical data to support use – not adopted widely
57
Q

zinc oxide and eugenol issues (2)

A
  • Free eugenol which remains can act as an irritant
  • Lose volume with time due to dissolution (apical seal diminished)
    • resins can modify this
58
Q

resin sealers

A
  • Long history of use – development of AH26
  • Epoxy Resin
  • Paste-Paste mixing
  • Slow setting - 8 hours
  • Good sealing ability
  • Good flow
  • Initial toxicity declining after 24 hours

used in GDH

59
Q

epiphany

A
  • dual cure dental resin composite sealer – used with Resilon
    • BisGMA
    • Ethoxylated BisGMA
    • Urethane-dimethacrylate UDMA
    • Hydrophilic difunctional methacrylates
    • Fillers of calcium hydroxide, barium sulphate, barium glass and silica
  • Requires self-etch primer - hard
60
Q

EndoRez

A
  • UDMA resin-based sealer
  • Hydrophilic
  • Good penetration into tubules
  • Biocompatible
  • Good radio-opacity
61
Q

calicum silicate sealers

A
  • High pH (12.8) during the initial 24 hours of the setting
  • Hydrophilic
  • Enhanced biocompatibility
  • Does not shrink on setting
  • Non-resorbable
  • Excellent sealing ability
  • Quick set
    • three to four hours
    • requires moisture
  • Easy to use
62
Q

medicated sealers

A
  • Sealers containing paraformaldehyde not acceptable
  • Lead and mercury components removed
  • Severe and permanent toxic effects on periradicular tissues
  • Sargenti paste, Endomethasone, SPAD

not used now - toxicity

63
Q

endodontic sealers

A
  • resin based
  • zinc oxide and eugenol
  • glass ionomer
  • calcium silicate
  • medicated
64
Q

what happens if endodontic conditions change? e.g.

A
  • root resportion
  • perforation - furcation, lateral
  • open apices - apexification

Developmental differences

  • Dens in dente ??
  • Wide canal and apex

Used bioceramic to plug apical portion and backfill with GP

65
Q

2 types of MTA

(mineral trioxide aggregate)

A

porcelain cement derivative

  • grey
  • white
66
Q

grey MTA

A

Earliest formulations

  • Less toxic than Portland cement
  • Better setting characteristics
  • Tooth discolouration – stain – not appropriate anteriorly

components

  • Tricalcium silicate
  • Dicalcium silicate
  • Tricalcium Aluminate
  • Tetracalcium aluminoferrite
  • Bismuth oxide
67
Q

white MTA

A
  • Smaller particle size
  • Reduced discolouration still slight

Components

  • Tricalcium silicate
  • Dicalcium silicate
  • Calcium aluminate
  • Bismuth oxide
  • Calcium sulphate dehydrated
68
Q

setting reaction MTA

A

Hydraulic cements

Composed of several phases

  • When mixed with water a chemical reaction occurs between these phases and water (Hydration)
    • White and grey MTA undergo different setting reactions
  • Extended setting times – have been modified by manufacturers to try and reduce set

works well in moisture control hard – apical, perforation

cannot use in oral cavity – be washed out before set

69
Q

MTA pro and con

A

works well in moisture control hard – apical, perforation

cannot use in oral cavity – be washed out before set

70
Q

biodentine improvement on MTA

A

bioceramic cement to reduce issues of MTA – faster setting (mins not hours), reduced staining – direct pulp cap

71
Q

tissue response to MTA

A
  • Induce osteogenesis bone formation
    • Change in pH – HA layer formed on surface

MTA plug with cementum directly on top

72
Q

ideal root filling?

A
  • Various endodontic materials have been used
    • Generally a core material and sealer
  • Always sealer used to create a fluid-tight seal

AAE states NSRCT “involves the use of biologically acceptable chemical and mechanical treatment of the root canal system to promote healing and repair of the periradicular tissues”

  • ZOE sealers dissolve – avoid
  • Resin sealers, bioceramic sealers adequate and comparable
73
Q

MTA as orthograde obturation?

A

BDS3 DMS (9 decks)

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