Endodontic Materials Flashcards Preview

BDS3 Dental Materials Science > Endodontic Materials > Flashcards

Flashcards in Endodontic Materials Deck (18)
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1
Q

work hardening

A

strengthening of a metal by plastic deformation
- crystal structure dislocation
- dislocations interact & create obstructions in crystal lattice
- resistance to dislocation formation develops
- observed as work hardening

2
Q

martensite v austenite

A

crystal lattice structure altered by temp / stress
character & proportions determine mechanical properties of metal
martensite = soft & ductile, easily deformed
austenite = strong & hard

3
Q

components of endodontic rotary instrument

A

taper - diameter change along working surface
flute - groove to collect dentine & soft tissue
leading / cutting edge - forms & deflects dentine chips
land - surface extending between flutes
relief - reduction in surface of land
helix angle - angle cutting axis forms with long axis of file

4
Q

irrigant properties

A
  • facilitate removal of debris
  • lubrication
  • dissolution of organic & inorganic matter
  • penetration to canal periphery
  • kill bacteria / yeast / viruses
  • biofilm disruption
  • biological compatibility
  • does not weaken tooth structure
5
Q

sodium hypochlorite NaOCl

A

ionises in water into Na+ & OCl- (hypochlorite ion)
HOCl then formed is responsible for antibacterial activity

6
Q

effect of NaOCl

A

effect on organic material
inability to remove smear layer by itself
possible effect on dentine properties

7
Q

factors important for NaOCl function

A
  1. concentration
  2. volume
  3. contact
  4. mechanical agitation
  5. exchange
8
Q

what happens during canal prep for obturation

A

smear layer formed during prep
this is organic pulpal material & inorganic dentinal debris
superficial 1-5um with packing into tubules
includes bacterial contamination, substrate & interferes with disinfection
prevents sealer penetration

9
Q

options for removal of smear layer

A
  1. 17% EDTA
  2. 10% citric acid
  3. MTAD
  4. sonic & ultrasonic irrigation
10
Q

properties of an ideal obturation material

A

easily manipulated with ample working time
dimensionally stable with tissue fluids
seals canal laterally & apically
non irritant
impervious to moisture
unaffected to tissue fluids
inhibits bacterial growth
radiopaque
does not discolour tooth
sterile
easily removed (if necessary)

11
Q

GP used in dentistry

A

beta form
naturally occurring is alpha form but when heated above 65o and cooled rapidly is recrystallises as beta form

12
Q

GP cones

A

20% GP
65% zinc oxide
10% radiopacifiers
5% plasticisers

13
Q

sealer functions

A

seals space between dentinal wall & core
fills voids & irregularities in canal, lateral canals and in between GP points used in lateral condensation
lubricates during obturation

14
Q

properties of an ideal sealer

A
  • exhibits tackiness to provide good adhesion
  • establishes a hermetic seal
  • radiopacity
  • easily mixed
  • no shrinkage on setting
  • non staining
  • bacteriostatic
  • slow set
  • insoluble in tissue fluids
  • tissue tolerant
  • soluble on retreatment
15
Q

zinc oxide eugenol as sealer

A

free eugenol remains & can act as an irritant
loses volume with time due to dissolution (resins can modify this)

16
Q

glass ionomer sealers

A

advocated due to dentine bonding properties
removal upon re tx is difficult
minimal antimicrobial activity
little clinical data to support use

17
Q

resin sealers

A

AH +
epoxy resin with paste - paste mixing
slow setting ~ 8hrs
good sealing ability
good flow
initial toxicity declining after 24hrs

18
Q

MTA white

A

this is a bioceramic cement
smaller particle size than MTA grey and has reduced tooth discolouration
e.g. tri / dicalcium silicate, calcium aluminate