Instrumentation of the Root Canal System Flashcards
why is instrumentation used in the root canals
removed infected soft and hard tissue, give disinfecting irrigant access to apical canal space, create space for the delivery of medicaments and subsequent obutarion, raise integrity of radicular structures
get all stuff out, widen to allow bleach, make easier to kill, keep in same shape as before
design objectives of instrumentation of RC system
- create a continuously tapering funnel shape
- maintain apical foramen in orginal position
- keep apical opening as small as possible
chemo vs mechanical preparation
chemo = kill organisms, remove smear layer
mechanical = prepare shape, flush out
what is the aim of chemomechanical preparation
shape canal, allow delivery of NaOCl to working length and create shape to obturate
what are the challenges of root canal preparation
complex, number length curvature and diameter of root canals varies considerably
estimated working length
estimated length at which instrumentation should be limited.
obtained by measuring pre-op radiographs to determine distance between coronal reference point and radiographic apex then subtracting 1mm
corrected working length
length at which instrumentation and subsequent obutration should be limited
obtained by electronic apex locator and/or working length radiograph
master apical file
largest diameter file taken to working length and therefore represents final prepared size of apical portion of canal at WL
types of motions used in mechanical preparation
- filing
- reaming
- watch winding
- balanced force motion
- envelope of motion
watch winding technique
back and forward oscillation of 30-60*
light apical pressure, effective with K files, useful for passing small files through canals
barbed broach instrument
for extirpation not enlarging
tapered round shaft, not engage canal walls
stainless steel instruments
16mm cuttig flutes
hedstrom file, reamer, k-file
hedstrom file
filing motion, cuts on withdrawl
good cutting efficiency
iatrogenic damage so no longer used for canal preparation
useful for removing gutta percha or fractured instruments in retreatment
reamer
twisting tapered triangle shaft
cutting edges parallel to cutting edge
contact with walls for effectiveness
if it binds, it breaks
k-files
cutting edge perpendicular to long axis
filing motion, withdrawn while applying lateral pressure, repeat until canal enlarged
nickel titanium instruments
super elasticity, can be strained more than other alloys before permanent deformation
curved canals for less lateral force exerted
less transportation, zipping, ledging
more centrally placed preparation in harmony with original canal shape
what are the components of endodontic rotary instruments
- taper
- flute
- leading/cutting edge
- land
- relief
- helix angle
taper and flute component definitions
taper = diameter change along working surface
flute = groove to collect dentine and soft tissue
leading/cutting edge and land component definitions
leading/cutting edge = forms and deflects dentine chips
land = surface extending between flutes
relief and helix angle component defintions
relief = reduction in surface of land
helix angle = angle cutting axis forms with long axis of file
advantages of NiTi vs SS
increased flexibility in larger sizes and tapers, increased cutting efficiency
good safety if used appropriately, can be more user-friendly with fewer instruments and simple sequences
disadvantages of NiTi
instrument fracture, expense, access difficult in posterior teeth, unsuitable for complex canal anatomy
what is true reciprocation
adv and disadv
mimic of manual movement
reduces risks associated with continuously rotating a file through canal curvatures
decreased cutting efficiency, increased inward pressure required, limited capacity to auger debris out of canal
how do you create a glide path
confirm straight line access, explore anaotmy, introduce 10-25 files to resistance, coronal flare, size 10 watch winding to establish apex, irrigate and repeat using size 15-20
what is torsional stress
extensive instrument surface encounters excessive friction on canal walls, instrument tip is larger than canal section to be shaped, tip may lock and torque exceeds critical level
what is flexural stress
repeated cyclic metal fatigue, cannot be influenced by clinician
what is cyclic fatigue
freely rotating in curvature, generation of tension/compression
