endodontic materials 2

Question 1

why must the smear layer be removed from root canal preparations

Answer 1

risks inadequate sealer penetration and bacterial contamination

Question 2

why must the canals be free of sodium hypochlorite before introducing EDTA

Answer 2

they can interact and form parachloroaniline which is cytotoxic and carcinogenic

Question 3

what are the two crystalline forms of gutta percha and how are they achieved

Answer 3

alpha and beta
alpha is the naturally occuring form
when heated above 65 degrees celsius it melts, if cooled slowly it returns to alpha phase but if it cools rapidly it changes to beta phase

Question 4

is alpha or beta gutta percha used in dental settings

Answer 4

betta

Question 5

what is gutta percha cones composed of

Answer 5

gutta percha
zinc oxide
radiopacifiers
plasticisers

Question 6

purpose of endodontic sealers

Answer 6

seal space between core material and dentinal wall, fills voids and irregularities in canal and space between GP points
also provides lubrication during obturation

Question 7

why are zinc oxide and eugenol sealers not the top choice of endodontic sealer

Answer 7

lose volume over time risking the apical seal
however they have a strong antimicrobial affect

Question 8

discuss the pros and cons of resin sealers

Answer 8

pros: good seal, good flow
cons: slow setting, initial toxicity but this declines after 24hours

Question 9

discuss the pros and cons of calcium silicate sealers (new kid)

Answer 9

pros: high pH in 1st 24 hours thought to have antimicrobial effect, hydrophillic (attracted to moisture in dentinal tubules), excellent seal, no shrink, easy to use
cons: expensive

Question 10

what material might be used for apexification or lateral perforation repair

Answer 10

MTA
(grey = old composition, white = new)