Root Canal Instrumentation Flashcards
one anatomical consideration when thinking of instrumentation
root canal naturally tapers apically
time for disease resolution (eg. apical periodontitis) after RCT
months to yrs
what 2 things need be mentioned to pt
- success rate of procedure
2. in case it fails… what happens
gold standard for chemical preparation of the canal
2% Hypochlorite (bleach)
precautions when using Hypochlorite
- keep within rubber dam pocket - stains clothes
- burns tissue is ingested (hence rubber dam)
- dissolves pulp - this property is what also makes it so suitable
why avoid overpreparing
not enough structure remaining - RCT will break
first 3 aims of preparation
- complete yet conservative access to pulp chamber
- straight-line access to root canals
- creation of continuous taper corono-apically
next 3 aims of preparation
- maintaining original canal anatomy
- minimal enlargement of apical constriction
- disinfection of root canal system using Irrigants and Instruments
Bystrom 1981
- saline irrigant - not sufficient, 50% only bacteria free at visit 5
- cannot use instrument disinfection alone
why cannot use instrumentation alone for disinfection
files contact only 60% of walls of canal
what must one always use in combination with instrument disinfection
1.antimicrobial irrigant (and medicament if necessary)
what can be said then about the role of instrumentation?
provides the MECHANICAL ACCESS for disinfection
two metals used in endo files
Stainless steel Nickel titanium (1988)
types of stainless steel files
- Barbed broaches
- Hedstrom files
- K files
- Reamers (hand or engine driven)
disadvantage of stainless steel files + one advantage
very stiff, not flexible enough through root canal at greater thicknesses.
+greater cutting efficiency than Nickel Titanium files
taper used on stainless steel files
0.2 (2%). anything higher will make it too rigid
ideal taper for a file
6 - 8% mimicking biological taper
advantage of Nickel titanium
more flexible - can make use of 6-7% taper efficiently
what sort of standardization are K files subjected to
ISO standardization
what does ISO standardization comprise
- color coded APICAL size
- length
- taper
- length of cutting shaft
3 commonly used lengths of K files
21
25
31 mm
3 common APICAL sizes
#10 #15 #20
brand of K file used in DDUH
Maillefer Flexofile (Dentsply)
two hand filing techniques
- watch-winding: reciprocal for negotiation
2. Balanced-Force Technique
who + when introduced balanced force technique?
Roane
1985
second category of instrumentation?
rotary (NiTi) files
disadvantage of rotary NiTi files
- don’t cut as well
2. more difficult to see when damaged
advantage of NiTi rotary files
greater taper possible
“Crown Down Preparation”
removal of bacteria starting coronally and moving down apically (as opposed to starting at the apex and moving out)
why not ‘true’ Crown Down preparation?
as we step back from the apex
4 advantages of crown down prep
- rapid irrigant penetration
- prevents instruments from binding coronally
- consistent LENGTH CONTROL
- straight line access to apex
what technique we use for crown down prepping
‘Modified double-flare technique’ with Balanced force
3 preparation errors
- zipping of apex (transportation)
- ledge formation
- stripping
stripping /strip perforations
caused by excessive flaring of canal w rotary instruments; mostly inaccessible; treated w MTA
zipping
transportation of apical portion of canal.
causes: existing curved canal that has been straightened
ledge formation
- inadequate straight line access
- inadequate irrigation/lubrication
- using straight instruments in curved canal.
- packing debris in apical portion of canal.
- rapid advancement in file sizes
- skipping file sizes
how to avoid these (x5)
- use NiTi files
- Balanced force technique
- smaller files in curved canals
- irrigate profusely
- ensuring patency (condition of being open or unobstructed)
list 3 endo burs
- Trans-metal bur [aka beaver bur]
- Endo-Z bur (blunt end)
- long shank bur [aka Goose neck bur]
advantage of long shank bur on plastic teeth
less damage
how to detect canal that bifurcates close to apex
need of microscope
principle of Bleeding technique for determining working length
necrotised pulp does not bleed. bone will. introduce file until meet resistance (aka bone) take out and check for bleeding
first 4 steps in RCT
- tooth assessment
- LA
- rubber dam
- access opening
next 3 steps in RCT
- Explore anatomy & locate/negotiate canals
- achieve straight line access to canals
- chemo-mechanical debridement
last 3 steps in RCT
- +/- interim dressing
- obturation
- permanent restoration
