Root Canal Instrumentation

Question 1

one anatomical consideration when thinking of instrumentation

Answer 1

root canal naturally tapers apically

Question 2

time for disease resolution (eg. apical periodontitis) after RCT

Answer 2

months to yrs

Question 3

what 2 things need be mentioned to pt

Answer 3

1. success rate of procedure

2. in case it fails… what happens

Question 4

gold standard for chemical preparation of the canal

Answer 4

2% Hypochlorite (bleach)

Question 5

precautions when using Hypochlorite

Answer 5

1. keep within rubber dam pocket - stains clothes
2. burns tissue is ingested (hence rubber dam)
3. dissolves pulp - this property is what also makes it so suitable

Question 6

why avoid overpreparing

Answer 6

not enough structure remaining - RCT will break

Question 7

first 3 aims of preparation

Answer 7

1. complete yet conservative access to pulp chamber
2. straight-line access to root canals
3. creation of continuous taper corono-apically

Question 8

next 3 aims of preparation

Answer 8

4. maintaining original canal anatomy
5. minimal enlargement of apical constriction
6. disinfection of root canal system using Irrigants and Instruments

Question 9

Bystrom 1981

Answer 9

1. saline irrigant - not sufficient, 50% only bacteria free at visit 5
2. cannot use instrument disinfection alone

Question 10

why cannot use instrumentation alone for disinfection

Answer 10

files contact only 60% of walls of canal

Question 11

what must one always use in combination with instrument disinfection

Answer 11

1.antimicrobial irrigant (and medicament if necessary)

Question 12

what can be said then about the role of instrumentation?

Answer 12

provides the MECHANICAL ACCESS for disinfection

Question 13

two metals used in endo files

Answer 13

Stainless steel
Nickel titanium (1988)

Question 14

types of stainless steel files

Answer 14

1. Barbed broaches
2. Hedstrom files
3. K files
4. Reamers (hand or engine driven)

Question 15

disadvantage of stainless steel files + one advantage

Answer 15

very stiff, not flexible enough through root canal at greater thicknesses.
+greater cutting efficiency than Nickel Titanium files

Question 16

taper used on stainless steel files

Answer 16

0.2 (2%). anything higher will make it too rigid

Question 17

ideal taper for a file

Answer 17

6 - 8% mimicking biological taper

Question 18

advantage of Nickel titanium

Answer 18

more flexible - can make use of 6-7% taper efficiently

Question 19

what sort of standardization are K files subjected to

Answer 19

ISO standardization

Question 20

what does ISO standardization comprise

Answer 20

1. color coded APICAL size
2. length
3. taper
4. length of cutting shaft

Question 21

3 commonly used lengths of K files

Answer 21

21
25
31 mm

Question 22

3 common APICAL sizes

Answer 22

#10
#15
#20

Question 23

brand of K file used in DDUH

Answer 23

Maillefer Flexofile (Dentsply)

Question 24

two hand filing techniques

Answer 24

1. watch-winding: reciprocal for negotiation

2. Balanced-Force Technique

Question 25

who + when introduced balanced force technique?

Answer 25

Roane | 1985

Question 26

second category of instrumentation?

Answer 26

rotary (NiTi) files

Question 27

disadvantage of rotary NiTi files

Answer 27

1. don't cut as well | 2. more difficult to see when damaged

Question 28

advantage of NiTi rotary files

Answer 28

greater taper possible

Question 29

"Crown Down Preparation"

Answer 29

removal of bacteria starting coronally and moving down apically (as opposed to starting at the apex and moving out)

Question 30

why not 'true' Crown Down preparation?

Answer 30

as we step back from the apex

Question 31

4 advantages of crown down prep

Answer 31

1. rapid irrigant penetration 2. prevents instruments from binding coronally 3. consistent LENGTH CONTROL 4. straight line access to apex

Question 32

what technique we use for crown down prepping

Answer 32

'Modified double-flare technique' with Balanced force

Question 33

3 preparation errors

Answer 33

1. zipping of apex (transportation) 2. ledge formation 3. stripping

Question 34

stripping /strip perforations

Answer 34

caused by excessive flaring of canal w rotary instruments; mostly inaccessible; treated w MTA

Question 35

zipping

Answer 35

transportation of apical portion of canal. | causes: existing curved canal that has been straightened

Question 36

ledge formation

Answer 36

1. inadequate straight line access 2. inadequate irrigation/lubrication 3. using straight instruments in curved canal. 4. packing debris in apical portion of canal. 5. rapid advancement in file sizes 6. skipping file sizes

Question 37

how to avoid these (x5)

Answer 37

1. use NiTi files 2. Balanced force technique 3. smaller files in curved canals 4. irrigate profusely 5. ensuring patency (condition of being open or unobstructed)

Question 38

list 3 endo burs

Answer 38

1. Trans-metal bur [aka beaver bur] 2. Endo-Z bur (blunt end) 3. long shank bur [aka Goose neck bur]

Question 39

advantage of long shank bur on plastic teeth

Answer 39

less damage

Question 40

how to detect canal that bifurcates close to apex

Answer 40

need of microscope

Question 41

principle of Bleeding technique for determining working length

Answer 41

necrotised pulp does not bleed. bone will. introduce file until meet resistance (aka bone) take out and check for bleeding

Question 42

first 4 steps in RCT

Answer 42

1. tooth assessment 2. LA 3. rubber dam 4. access opening

Question 43

next 3 steps in RCT

Answer 43

5. Explore anatomy & locate/negotiate canals 6. achieve straight line access to canals 7. chemo-mechanical debridement

Question 44

last 3 steps in RCT

Answer 44

8. +/- interim dressing 9. obturation 10. permanent restoration