Endodontic Materials Flashcards
What are the Endodontic Material Categories?
- Instruments
- Irrigants
- Intra-canal medicaments
- Obturation materials
- Sealers
- Pulp Capping materials
- Root-end filling materials
What are the endodontic instruments used for?
- For mechanical phase of chemo mechanical disinfection
- Metal files used to remove soft and hard tissues
- Removes micro-organisms
- Creates spaces for disinfectants/ medicaments
- Creates appropriate shape for obturation
What is Stress?
- Deforming force measured across a given area
- Tensile/compressive/shear/torsional
Stress = F/A
What is the stress concentration point in regard to endodontic instrument?
- Abrupt changes in the geometric shape of a file that leads to a higher stress at that point
- Can be due to notch and change in root shape
What is Strain?
- Response of a material to stress
- Amount of deformation a file undergoes
Strain = Delta L / L
What is Elastic Limit in regard to metal file?
- A set value representing the maximal strain that when applied to a file, allows the file to return to original dimensions
- File still has fracture point if stress vs strain too much
What is elastic deformation?
- Reversible deformation that does not exceed elastic limit
What is plastic deformation?
- Permanent bond displacement occurring when elastic limit exceeded
What is the Plastic Limit?
- Point at which a plastic deformed file breaks
What is Cyclic Fatigue?
- Stress and strain, and deformation induced in a material by cyclic loading
- File is freely rotating in a curvature
- Generation of tensions/ compression cycles
- Leads to cyclic fatigue and eventually failure
What is Torsional fatigue?
- The damage to the torque shafts caused by torsional loading which leads to a different form of throwing stress
What is stainless steel for the Kfiles made of?
- 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
How are kfiles manufactured?
- Machined stainless steel wire
- Square/ Triangular
- Twisted
- Work hardening occurs
What is the process of Work hardening?
- Strengthening of a metal by plastic deformation
- Crystal structure dislocation occurs
- Dislocations interact and create obstructions in crystal lattice
- Resistance to dislocation formation develops
- Observed work hardening
What is Nitinol?
- Equiatomic alloy of nickel and titanium
What are the properties of Nitinol?
Exotic metal - Does not conform to typical rules of mettalurgy
Super-elasticity - Application of stress does not result in usual proportional strain
What is mettalurgy?
- Branch of science and technology concerned with properties of metals and their production and purification
What is shape memory?
- Alloys are materials that can be deformed at one temperature but when heated or cooled, return to their original shape.
What is the shape memory of KFile?
- At or below room temp the instrument is very malleable and has relaxed serpentine shape
- Warmer temp (>95degreesF), the instrument transitions to a more robust serpentine shape
What are the properties of Irrigant?
Plays central role for 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
Why is Sodium Hypochlorite (NaOCl) used for Irrigant?
- 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
Why do we need to prepare 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
How do you 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!
What are the 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
What are Gutta-Percha cones made of?
- 20% Gutta-percha
- 65% Zinc Oxide
- 10% Radiopacifiers
- 5% Plasticizers
- Standardised, non-standardised and size-matched
What are the functions of Sealers?
- 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
What are the properties of 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
What are the benefits of Zinc oxide and Eugenol as sealer?
- Radio-opacity < GP
- Rosin or Canada Balsam added to increase dentine adhesion
- Is a corticosteroid
- Zinc oxide effective antimicrobial and is cytoprotectant
Positive and negative of glass ionomer sealer?
- Advocated due to dentine bonding properties
- Removal upon retreatment is difficult
- Minimal antimicrobial activity
Positive and negative of epoxy resin sealer?
- Long history of use
- Slow setting - 8 hours
- Good sealing ability
- Good flow
What is EndoRez? Give positive and negative
- UDMA resin-based sealer
- Hydrophilic
- Good penetration into tubules
- Biocompatible
- Good radio-opacity
What are some Resin Sealers?
- BisGMA
- Ethoxylated BisGMA
- Urethane-dimethacrylate UDMA
- Hydrophilic difunctional methacrylates
- Fillers of calcium hydroxide, barium sulphate, barium glass and silica
What are some properties of 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
What sealers are not acceptable?
- Sealers containing Paraformaldehyde
- Severe and permanent toxic effects on periradicular tissues
What are the two colours of mineral trioxide aggregate?
- Grey
- White
What is an example of MTA?
Tricalcium silicate
Dicalcium silicate
