Endodontic Materials

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

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

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

• 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

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

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

• concentration • volume • contact • mechanical agitation • exchange

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

• 17% EDTA • 10% citric acid • MTAD • sonic & ultrasonic irrigation

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)

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

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

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

• 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

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

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

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

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