endodontic materials Flashcards
(28 cards)
categories of endo materials
Instruments
Irrigants
Intra-canal medicaments
Obturation materials
Sealers
Pulp Capping materials
Root-end filling materials
endo instruments
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
physical properties of endo materials
Stress - tensile/compressive/shear
Stress concentration point - abrupt changes in the geo shape that leads to higher stress in that point
Strain = response to stress = how much deformation undergoes
Elastic limit = maximal strain that when applied to file, allows file to return to original dimensions
Elastic deformation = reversible deformation that does not exceed elastic limit
Shape memory
Plastic deformation
Plastic limit
cyclic fatigue
Freely rotating in a curvature
Generation of tension/compression cycles
Cyclic fatigue
Failure
endo instrument fracture causes
- 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
stainless steel hand files
Alloy of iron, carbon and chromium
Nickel may also be present
Improved carbon steel – rusting
13-26% chromium prevents rusting
Passivation layer of chromium oxide
work hardening = strengthening by deformation
dislocations interact and create obstructions in crystal lattice
resistance to dislocation formation develops
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
Temperature-dependent structures martensite and austenite
Crystal lattice structure altered by temperature or stress
shape memory
shape memory alloys are materials that can be deformed at one temperature but when heated or cooled, return to their original shape.
components of an endo rotary instrument
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
irrigant role in endo 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
sodium hypochlorite (NaOCl)
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
Effect on organic material
Inability to remove smear layer by itself
Possible effect on dentine properties
factors important for NaOCl function
concentration
volume
contact
mechanical agitation
exchange
removal of 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!
irritant interactions
Interaction with NaOCl forms para-chloroaniline
Cytotoxic and carcinogenic
Uncertain bioavailability
properties of an ideal obturation material
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
gp
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 65C 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
gp cones
20% Gutta-percha
65% Zinc Oxide
10% Radiopacifiers
5% Plasticizers
Standardised, non-standardised and size-matched
sealer function
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
properties on an 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
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
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
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 – resins can modify this
GI sealers
advocate due to dentine bonding properties
Removal upon retreatment is difficult
Minimal antimicrobial activity
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
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
EndoRez is a UDMA resin-based sealer
Hydrophilic
Good penetration into tubules
Biocompatible
Good radio-opacity
calcium 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
