Endodontic Materials Flashcards
7 endodontic material categories
- Instruments
- Irrigants
- Intra-canal medicaments
- Obturation materials
- Sealers
- Pulp Capping materials
- Root-end filling materials
5 endodontic instruments uses
- 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
8 key physical properties
- Stress
- Stress concentration point
- Strain
- Elastic limit
- Elastic deformation
- Shape memory
- Plastic deformation
- Plastic limit
stress
deforming force measured across a given area
tensil/compressive/shear/torsional
stress concentration point
abrupt changes in geometric shape of a file that leads to higher stress at that point
strain
response of a material to stress
anount of deformation a file undergoes
elastic limit
a set value representing the maximal strain that when applied to a file, allows to return to original dimensions
elastic deformation
reversible deformation that does not excess elastic limit
shape memory
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
plastic deformation
permanent bond displacement occurring when elastic limit exceeded
plastic limit
the point at which a plastic deformed file breaks
leads to instrument separation
- clinical failure
cylic fatigue
freely rotating in a curvature
generation of tension/compression cycles
cyclic fatiugue = failure
torsional fatigue
bind to dentinal wall
rotate but not bond portion
- plastic deformation between 2 parts = failure
7 prevention methods for endodontic instrument failure
- 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
6 classifications of endodontic instruments
- 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
stainless steel
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
2 manufacturing techniques of stainless steel endo instruments
- Machined stainless steel wire
- Cut into Square/Triangular or Twisted
- Work-hardening occurs – improves
or
- Machine stainless steel wire into desired shapes
- Work hardening
work hardening
- 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
nitinol
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
NiTi Crystal Structure
- 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
6 components of endodontic rotary instruments
- taper
- flute
- leading/cutting edge
- land
- relief
- helix angle
taper
diameter change along working surface
flute
groove to collect dentine and soft tissue
leading/cutting edge
forms and deflects dentine chips
land
surface extending between flutes
relief
reduction in surface of land
helix angle
angle cutting axis forms with long axis of file
impact of subtle difference in endodontic instrument features
large change in characteristics of instrument
positive helix/rake angle provides
active cutting surface action of the K3
third radial land role
stabilises and keep the instrument centred in the canal and minimises ‘over-engagement’
wide radial land provides
blade support while adding peripheral strength so resist torsional and rotary stresses
radial land relief
reduces friction on the canal wall
properties of irrigants key to role
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
formula for sodium hypochlorite
NaOCl
NaOCl irrigant reaction
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
what component of NaOCl is responsible for antibacterial activity
HOCl
3 negatives of NaOCl
- Effect on organic material
- Inability to remove smear layer by itself
- Possible effect on dentine properties
5 factors key to NaOCl function
- concentration
- volume
- contact
- mechanical agitation
- exchange
preparation of the canal for obturation
- 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
4 ways to remove smear layer
- 17% EDTA
- 10% Citric Acid
- MTAD (Mixture of a Tetracycline isomer, an Acid, and a Detergent
- Sonic and Ultrasonic irrigation
Watch apical control!
5 things used during canal irrigation
- sodium hypochlorite
- EDTA
- chlorhexidine digluconate
- sterile saline
NaOCl and EDTA not present at same time in canal as EDTA effects NaOCl therapeutic benefits
sodium hypochlorite as irrigant
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
EDTA as irrigant
17%
- smear layer removal
3ml penultimate rinse for 1 min
corodyl as irrigant
chlorhexidine digluconate 0.2%
used for checking dam integrity and disinfect tooth surface
gluco-chex as irrigant
chlorhexidine digluconate 2%
- antimicrobial
use when suspect iatrogenic damage
- but only when NaOCl contraindicated
sterile saline in irrigation
used to wash out canal
suspect hypochlorite accident
volume as required
irrigant interaction
Interaction with NaOCl forms para-chloroaniline
- Cytotoxic and carcinogenic
- Uncertain bioavailability
11 properties for ideal obturation materials
- 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
Gutta percha
history
- 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
- Alpha phase heated above 65°C melts into amorphous phase
- Beta phase used in commercially prepared dental gutta-percha
- Alpha phase is the naturally occurring form
gutta percha cones
components
- 20% Gutta-percha
- 65% Zinc Oxide
- 10% Radiopacifiers
- 5% Plasticizers
Standardised, non-standardised and size-matched
3 sealer functions
- 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
11 properties of ideal sealer
- 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
zinc oxide and eugenol
sealer
properties
- 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
Zinc oxide as antimicrobial and cytoprotective functions
- 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
zinc oxide and eugenol
setting
issues
- 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
Glass ionomer sealers
- Advocated due to dentine bonding properties
- Removal upon retreatment is difficult
- Minimal antimicrobial activity
- Little clinical data to support use – not adopted widely
zinc oxide and eugenol issues (2)
- Free eugenol which remains can act as an irritant
- Lose volume with time due to dissolution (apical seal diminished)
- resins can modify this
resin sealers
- 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
epiphany
- 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
EndoRez
- UDMA resin-based sealer
- Hydrophilic
- Good penetration into tubules
- Biocompatible
- Good radio-opacity
calicum silicate sealers
- 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
medicated sealers
- 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
endodontic sealers
- resin based
- zinc oxide and eugenol
- glass ionomer
- calcium silicate
- medicated
what happens if endodontic conditions change? e.g.
- 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
2 types of MTA
(mineral trioxide aggregate)
porcelain cement derivative
- grey
- white
grey MTA
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
white MTA
- Smaller particle size
- Reduced discolouration still slight
Components
- Tricalcium silicate
- Dicalcium silicate
- Calcium aluminate
- Bismuth oxide
- Calcium sulphate dehydrated
setting reaction MTA
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
MTA pro and con
works well in moisture control hard – apical, perforation
cannot use in oral cavity – be washed out before set
biodentine improvement on MTA
bioceramic cement to reduce issues of MTA – faster setting (mins not hours), reduced staining – direct pulp cap
tissue response to MTA
- Induce osteogenesis bone formation
- Change in pH – HA layer formed on surface
MTA plug with cementum directly on top
ideal root filling?
- 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
MTA as orthograde obturation?
