Endo Materials Flashcards
When would you use chlorhexidine 2% as an irrigant?
When sodium hypochlorite is contra-indicated or you suspect iatrogenic damage
What is cyclic fatigue?
Cyclic fatigue occurs when there is repeated compression and tension cycles in the instrument that occur from rotation.
Causes unwanted work hardening and eventual failure.
What is torsional fatigue?
When the tip of an endo instrument gets stuck in a canal but the motor continues to rotate.
Eventually leads to fracture
Why is NiTi a desirable endo instrument?
It has super-elasticity - application of stress does not result in usual proportional strain.
Compared to SS instrument NiTi has:
Increased flexibility
Increased elasticity
Improved resistance to cyclic fatigue
What happens to a NiTi instrument when the temperature changes?
The characteristics change when the temperature changes.
Crystal lattice structure changes from martensite to austenite.
What is the main purpose of an irrigant in endodontics?
An anti-microbial agent that dissolves organic tissue within the root canal space.
What pH is sodium hypochlorite?
pH 9
Why must the smear layer be removed in endodontics?
Must be removed to facilitate adequate disinfection and sealer penetration into dentinal tubules
Why do you have to use EDTA following use of sodium hypochlorite?
Sodium hypochlorite does not completely remove smear layer by itself.
What are the properties of an ideal obturation material?
Easily manipulated with ample working time
Seals canal laterally and apically
Non-irritant
Impervious to moisture
Radio-opaque
Sterile
Easily removed if necessary
What is the most common obturation material used in dentistry and what form is it?
Gutta-percha
Beta form - rapidly cooled GP that re-crystallises
What are the functions of sealer?
Seals space between dentinal wall and core - creates a fluid-tight seal
Fills voids and irregularities in canal, lateral canals and between GP points used in lateral condensation
Lubricates during obturation
Give 2 examples of sealers used in dentistry?
Zinc oxide and eugenol
Epoxy resin - AH plus
What are some properties of the ideal sealer?
Tacky to provide good adhesion/ seal
Radio-opaque
Easily mixed
No shrinkage on setting
Slow set
Soluble on re-treatment
Bacteriostatic - does not encourage growth
What is the main problem with zinc oxide and eugenol?
Dissolution of material with time
Apical seal is diminished over time
What is a common material used for root-end filling?
MTA
What is the definition of working length?
The distance from a coronal reference point to the point at which the canal prep and obturation should terminate -between 1-2mm short of the apical foramen
What are 2 reasons to change the estimated working length to corrected working length during instrumentation?
Root curvature
Remnants of previous obturation materials in the canal
What are the timings for irrigation?
NaOCl 3% - 3ml for 1 minute
EDTA 17% - 3ml for 1 minute
NaOCl 3% - 30ml for 10 minute - soak
Why is non-setting CaOH an ideal inter-appointment medicament?
Highly radio-opaque
Anti-microbial
What are reasons for obturating?
To prove you got to working length
To seal dentinal tubules and canal space to prevent bacterial ingress
To eliminate space in the canal
What is cold lateral compaction?
Placing a single cone of GP with sealer in prepared canals and adding secondary GP cones that are compacted with a spreader.
What are the constituents of GP?
GP 20%
Zinc oxide 65%
Radio-pacifiers 10%
Plasticisers 5%
Why use sealer during CLC?
Sealer fills space/ voids between GP points
Lubricates for easier insertion of the GP points
Penetrates dentinal tubules, and accessory canals where the GP cannot
What component in stainless steel Endo-files are for corrosion resistance?
Chromium
