Endo materials
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What is strain
Response of a material to stress
What is elastic deformation
Reversible deformation that does not exceed elastic limit
What is plastic deformation
Permanent bond displacement occurring when elastic limit if exceeded
What is the plastic limit
The point at which a plastic deformed file breaks
What is Nitinol
Equiatomic alloy of nickel and titanium
What are the properties of martensite and austenite
Austenite form, it is soft and ductile and easily deformed Martensite form is quite strong and hard
What is shape memory
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 angle called which is formed btween the cutting axis and long axis
Helix angle
What is the purpose ofland releif
Reduces friction on the canal wall
What is the wide radial land for
Porvides blade support while adding peripheral strength to resist torsional and rotary stresses
What part of the instrument provides stability
Third radial land
What are the ideal irrigant 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
What percentage of EDTA is used
17%
When is sterile saline recommended
To wash out canal is NaCL accident suspected
What amount of EDTA is used for the penultimate rinse
3ml
What is the main property of NaCL
Dissolve organic material bactericidal
What is the main purpose of EDTA
To remove the smear layer
What are the ideal properties of an 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 is GP
Produced from the juice of trees of the sapodilla family
What isthe composition of GP cones
20% GP 65% Zinc oxide 10% radiopacifiers 5% Plasticizers
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 ideal properties of a 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 examples of some sealers
Zinc oxide and eugenol GI Resin sealers - AH plus
What are the benefits of zinc oxide and eugenol
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