Endodontics

Question 1

what are the steps of RCT

Answer 1

1. diagnosis - with radiographs
2. access
3. extirpation
4. debridement + irrigate
5. drying
6. obturate + seal
7. restoration

Question 2

what is working length

Answer 2

distance from the coronal reference point to the point at which the canal prep and obturation should terminate (1-2mm short of apex ideally)

Question 3

what is the master apical file

Answer 3

it is the largest diameter file taken to WL
it represents the final prepared size of the apical portion of the canal at WL

Question 4

what is tug back when using the master apical file

Answer 4

the cone provides little resistance to its displacement or withdraw from root canal system

Question 5

what are some reasons for carrying out obturation of prepared root canal

Answer 5

• prevent bacteria ingress at apical foramina
• prevent coronal microleakage of bacteria
• prevents any bacteria remaining in the root canal system from multiplying and spreading

Question 6

which part of the root canal filling is the most important in ensuring long term success

Answer 6

coronal seal (2-3mm from apex)

Question 7

how do you decide b/w conventional vs post+core crown placement

Answer 7

conventional
= used when the tooth as a ferrule of a min 1.5-2mm (collar of dentine extending supragingivally 360deg around circumference of tooth)

post+core
= lack of ferrule for the crown to bond to - last resort

Question 8

what are the functions of a post

Answer 8

a post gains intra-radicular support for a restoration
it is present to retain the core

Question 9

what are the materials used for core + post

Answer 9

Core
= composte, amalgam, GI

Post
metal - cast gold, SS, brass, titanium
ceramic - alumina/zirconia
fibre - gladd, quartz, carbon

Question 10

what are types of Posts

Answer 10

prefabricated threaded parallel
prefabricated smooth tapered
indirect custom made

Question 11

what is a disadvantage of using a prefabricated smooth tapered POST

Answer 11

causes wedging

Question 12

what are 3 ways to determine POST LENGTH

Answer 12

LENGTH - should be 1/2 to 1/3 length of root or at least equal to the length of the crown

DIAMETER - should be no more than 1/3 of the root width at the narrowest point

APICAL - should have at least 4-5mm of GP left apically

Question 13

what are the problems associated with POSTS that are inserted that are too wide/too narrow

Answer 13

length is more important than width
BUT the longer/ narrow the post length there is an increased risk of perforation as root gets narrower

tooth is also weakened if root dentine is removed to place a larger post

Question 14

what are features of CaOH

Answer 14

gold standard intra-canal medicament. has pH 12.5

• provides prolonged anti-bacterial activity
• effective in removing tissue debris
• reduces inflammation via hydrolysis of liposaccharides
• easy to remove

Question 15

ideal properties of good sealer

Answer 15

exhibits tackiness + provides good adhesion
easily mixed
no shrinkage on setting
bacteriostatic
insoluble in tissue fluids
soluble on re- treatment
radiopacity

Question 16

components of GP

Answer 16

20% gutta percha
65% zinc oxide
10% radiopacifiers
5% plasticisers

Question 17

reasons for using sealer during cold compaction (obturation)

Answer 17

there is a limit to how much obturation that be be achieved laterally
- sealers will infiltrate dentine tubules the GP cannot pack into
- seals space between dentinal wall and core
- fills voids of canals, lateral canals and space b/w GP points
- provides lubrication for GP point insertion

Question 18

what are Herb Schilder’s endo principles

Answer 18

• access should be continuously tapered funnel shape
• apical foramen should be maintained in original position
• apical foramen should be kept as small as possible

Question 19

other than disinfection why is irrigation important

Answer 19

• provides lubrication
• removal of the smear layer
• dissolves pulp remnants + collagen

Question 20

what is the irrigant of choice in RCT

Answer 20

sodium hypochlorite 3%

Question 21

features to take in account when using irrigant

Answer 21

• ensure low pressure (lower than venous pressure in neck)
• slow irrigation
• needle short of WL (never pass deeper than few mm short of WL)

Question 22

what is the communication called between pulpal space and peri-radicular tissues

Answer 22

lateral canals

Question 23

what are potential causes of CWL changing during course of endo

Answer 23

root curvature
residual GP left in canal

Question 24

what are materials used for crowns

Answer 24

metal - gold , platinum, nickel, titanium, chromium
metal ceramic - porcelain fused metal

Question 25

factors important for the function of irrigant

Answer 25

concentration, volume, depth of penetration, time it is left in canal

Question 26

what are some problems after RCT/re-RCT

Answer 26

• Amount of remaining tooth structure - externally and internally
• Restoration type
• Lack or no ferrule (no tooth structure above the gum)
• Wide post holes e.g. re-RCT
• Endodontic complications - fractured instruments perforations, short/long root fillings

Question 27

what is the important cause of RCT failure

Answer 27

poor coronal seal, microleakage, bacteria ingress

Question 28

once a tooth is root treated how should it be monitored

Answer 28

take PAs yearly

Question 29

what are problems with posts

Answer 29

Perforation (angulation error)
Core fracture
Root fracture or crack
Post fracture

Question 30

how do you manage a post perforation

Answer 30

Repair – internal or external (periradicular surgery)
OR
Extraction