Instrumentation of Root Canal System Flashcards
what is the watch winding motion and when is it used
clockwise rotation of 30-60 degrees
anticlockwise rotation of 30-60 degrees
used with small instruments
what is the balanced force motion and when is it used
used with larger K files or pro-taper instruments
used in curved canals
clockwise turn of 90 degrees
apply apical pressure
anticlockwise turn of greater than 90 degrees
what is the aim of chemomechanical disinfection
shape canal
allow delivery of sodium hypochlorite to working length
create shape to obturate
how is EWL decided
by the pre-op radiograph
how is CWL decided
by using electronic apex locator or working length radiograph
what is the master file
largest diameter file taken to working length and therefore represents the final prepared size of the apical portion of canal at working length
what is the barbed broach file used for
used for extripating pulp
the elevated barbs engage the pulp and remove it from the canal
the largest sized broach that will fit freely in the canal is selected
what is the ISO colour code for hand files
white - 15 and 45
yellow - 20 and 50
red - 25 and 55
blue - 30 and 60
green - 35 and 70
black - 40 and 80
describe the ISO sized instruments
16mm cutting flute
named according to diameter at first rake
0.32 taper over the 16mm
what cross section do K-files cut in
square
describe K files
cutting edges perpendicular to long axis of instrument
what are the types of ISO files
H files
reamer
K files
what does the superelasticity of nickel titanium instruments allow
they can be strained more than other alloys before permanent deformation
can be placed in curved canals with less lateral force exerted
what are the components of an endodontic rotary instrument
taper
flute
leading/ cutting edge
land
relief
helix angle
what does the positive rake angle provide
active cutting action
what does the third radial land do
stabilises and keeps instruments centred in canal
what does the radial land relief do
reduces friction on canal wall
what does wide radial land provide
blade supporting while adding peripheral strength to resist torsional and rotary stresses
name four advantages of nickel titanium over stainless steel
increased flexibility in larger sizes and tapers
increased cutting efficiency
good safety in use
more user friendly
give four disadvantages of nickel titanium instruments for preparation
instrument fracture
expense
access difficult in posterior teeth
unsuitable for complex canal anatomy
what is true reciprocation and what does it do
mimics manual movement
reduces risks associated with continuously rotating file through canal curvatures
what are the guidelines for rotary instrumentation in canals
straight line access
sufficient space required to guide non-cutting tip of the rotary instrument
decide whether canal is single or multi canals
must use light touch and lots of sodium hypochlorite
what motion is observed in reciproc
150 degrees counterclockwise
30 degrees clockwise
what size of ISO file is required to go to working length before using R50
ISO 30
when is R25 used
in narrow canals where the canal is partially or completely invisible
what causes instrument separation
torsional stress (instrument tip larger than canal)
flexural stress (cyclic fatigue)
what is cyclic fatigue
rotating in free curvature
generating tension and compression cycles
failure of instrument
what probe is used to explore the access cavity and ascertain where the canal is
DG16 probe
name steps of modified double flare technique
DG16 probe to find canal
flush coronal part of canal with irrigant
pass 10K file into canal to ensure free passage
use rotary instrument to 2/3rds working length to shape coronal portion
irrigate and recapitulate
use smaller rotary instrument to move coronal preparation more apically
irrigate and recapitulate
again use smaller rotary instrument to lengthen preparation
place size 10 k file into canal to EWL and place apex locator on and wait til 0 or red band appears
CWL should be 0.5-1mm short of apex locator
use smaller K file and go to CWL
irrigate and recapitulate
how is apical tapering achieved
go to CWL with the smallest size file
each time you go up a size you move 1mm back from CWL
