Endodontics Materials Flashcards
what are endodontic instruments used for??
- mechanical phase of chemo mechanical disinfection
- used to remove soft & hard tissues
- removes micro-organisms
- creates spaces for disinfectants/medicaments
- creates appropriate shape for obturation
what is the elastic limit?
a set value representing the maximal strain that when applied to a file, allows the file to return to original dimensions
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 are the purposes of Irrigants in endodontic treatments?
- facilitate removal of debris
- lubrication
- dissolution of organic and inorganic matter
- penetration to canal periphery
- kill bacteria/yeasts/viruses
- biofilm disruption
What is the plastic limit?
The point at which a plastic deformed file breaks
How can endodontic instrument failure be prevented?
- training and proficiency in the NiTi system of choice
- create a manual glide path
- use an electric speed and torque controlled motor
- NiTi should be used in constant motion using gentle pressure
- use of rotary files in abruptly curved or dilacerated canals should be avoided
what are the classifications of endodontic instruments?
- manually operated
- low-speed instruments
- engine-driven nickel-titanium rotary instruments
- engine-driven instruments that adapt to canal shapes
- engine-driven reciprocating instruments
- ultrasonic instruments
What benefit does chromium give to stainless steel instruments?
prevents rusting
what is work hardening?
Strengthening of a metal by plastic deformation
- causes crystal structure dislocation
- these dislocations interact and create obstructions in crystal lattice
- resistance to dislocation formation develops
what is Nitinol?
Equiatomic alloy of nickel and titanium
What are shape memory alloys?
materials that can be deformed at one temperature but when heated or cooled, return to their original shape
what are the properties of the NiTi crystal structure?
- temperature dependant structures martensite and austenite
- crystal lattice structure altered by temperature or stress
what is the Martensite form of NiTi like?
soft and ductile
- easily deformed
what is the Austenitic form of NiTi like?
strong and hard
What are the components of an endodontic rotary instrument?
- taper
- flute
- leading/cutting edge
- land
- relief
- helix angle
what is a commonly used irrigant in Endodontic procedures?
Sodium Hypochlorite (NaOCl)
How is the smear layer removed typically? what else can be used?
17% EDTA
- (10% citric acid)
How long should EDTA be placed in the canal?
penultimate rinse for 1 min
what occurs if EDTA interacts with NaOCl?
Para-chloroaniline formed
- cytotoxic and carcinogenic
what would the properties of an ideal obturation material be?
- easily manipulated with ample working time
- dimensionally stable
- 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 is the most common endodontic core material?
Gutta-percha
What type of gupta-percha is used in dental procedures?
Beta phase gutta percha
What are the constituents of gutta percha cones?
- 20% gutta percha
- 65% zinc oxide
- 10% radiopacifiers
- 5% plasticisers
what is the function of sealers in endodontics?
- seals space between dentinal wall and core
- fills voids and irregularities in canal, lateral canals and between gutta percha points
- lubricates during obturation
What would the properties of an ideal sealer be?
- exhibits tackiness to provide good adhesion
- establishes a hermetic seal
- radiopacity
- easily mixed
- no shrinkage on setting
- non staining
- bactériostatique
- slow set
- insoluble in tissue fluids
- tissue tolerant
- soluble on retreatment
What is typically used as a sealer?
Resin sealers (epoxy resin)
Why are glass ionomer sealers problematic?
Removal upon re-treatment is difficult due to bonding to dentine
What resin sealer is used in the dental hospital ?
AH plus
how long does AH plus take to set?
8 hours
