Endodontic Materials Flashcards
What is cyclic fatigue?
Generation of tension/compression cycles which leads to work hardening and failure of the file.
What is torsional failure?
Results from continuing to turn the file beyond the elastic limit
What is work hardening?
Strengthening of a metal by plastic deformation
Causes crystal structure dislocation
Dislocations interact and create obstructions in a crystal lattice
Resistance to dislocation formation develops
What is nitinol?
An equiatomic alloy of nickel and titanium
Present in two forms - austenite and martensite
What are the components of a rotary endo instrument?
Taper - diameter change along working surface
Flute - groove to collect dentine & soft tissue
Cutting edge - forms and deflects dentine chips
Land - surface extending between flutes
Relief - reduction in surface of land
Helix angle
What is the purpose of irrigants?
Removal of debris Lubrication Dissolution of organic & inorganic matter Kill bacteria/yeasts/viruses Penetration to canal periphery Biofilm disruption
Name an irrigant used in endo.
Sodium hypochlorite (NaOCl)
What can be used to remove the smear layer formed during canal preparation?
17% EDTA (used for 1 min then back to hypochlorite)
10% citric acid
MTAD
Why can EDTA and NaOCl not be in the root canal at the same time?
They deactivate each other.
Must thoroughly dry canal between use.
What are the ideal properties of obturation materials?
Easily manipulated Ample working time Seals the canal laterally and apically Non-irritant Impervious to moisture Unaffected by tissue fluids Inhibits bacterial growth Radiopaque Does not discolour tooth Sterile Easily removed if necessary
What are the components of gutta percha?
20% gutta percha
65% zinc oxide
10% radiopacifiers
5% plasticisers
How is beta phase GP produced?
Alpha phase heated above 65 degrees melts into amorphous phase.
If cooled slowly - returns to alpha phase.
If cooled rapidly - recrystallises as beta phase.
What is resilon?
Resin-based system (bonds to the dentine in the canal).
Thermoplastic synthetic polymer based on polymers of polyester containing bio active glass & radiopaque fillers.
What is the function of sealer?
Seals space between dentinal wall and core.
Fills voids & irregularites in canal, lateral canals and between GP points used in lateral condensation.
Lubricates during obturation.
What are the ideal properties of a sealer?
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
