Define ‘elastic deformation’
Reversible deformation that does not exceed elastic limit
Define ‘plastic deformation’
Permanent bond displacement occurring when elastic limit exceeded
Define ‘plastic limit’
Point at which plastic deformed file breaks
What are the compositions of stainless steel?
- Iron
- Carbon
- Chromium >13% (prevents rusting)
- Nickel
What is the role of irrigation in endodontics?
- Facilitate removal of debris
- Lubrication
- Dissolution of organic and inorganic matter
- Penetration to canal periphery
- Kill bacteria/ yeasts/ viruses
- Biofilm disruption
What is the function of sodium hypochlorite?
~5%
- Removes organic material
- Antimicrobial
- Lubricant
How may the smear layer be removed?
17% EDTA
10% Citric acid
MTAD
Sonic and ultrasonic irrigation
What are the disadvantages of sodium hypochlorite?
- Cytotoxicity when expressed past apical foramen
- Bad smell and taste
- Metal corrosion
- Does not remove all smear layer
- May alter properties of dentine
What are the constituents of gutta percha?
- Gutta percha 20%
- Zinc oxide 65%
- Radiopacifiers 10%
- Plasticisers 5%
What is the functions of a sealer?
- Seals space between dentinal wall and core
- Fills voids and irregularites in canal, lateral canals and between GPs used in lat condens
- Lubricates during obturation
What type of sealers are available?
- ZOE
- GI sealers
- Resin sealers
- Calcium silicate sealers
- Medicated sealers
What are the advantages and disadvantages of ZOE as a sealer?
ADV
- Antimicrobial
- Removal on re-RCT is easy
DISADV
- Free eugenol = irritant
- Dissolution over time (resin can be added to resurrect)
What are the advantages and disadvantages of GI as a sealer?
ADV
- Bonds to dentine
DISADV
- Removal on re-RCT difficult
- Minimal antimicrobial activity
