SS and NiTi in endo Flashcards
what is the ISO specification for dentistry
ISO 3630-1, 2019
Types of instruments
standard instrument (taper 0.2)
taper instrument (uniform taper)
non taper instrument (cylindrical)
variable taper (more than one taper in working part)
shape instrument (contoured working part)
what is a hedstrom file
only cuts on retraction
temperature dependant phases of NiTi
austenitic - high temp
martensite - low temp
r-phase - intermediate temp
what phase is niti file in the canal
martensitic
what phase is niti file when removed from canal
austenitic
how are niti files manufactured
from niti wire
examples of 5th gen niti files (2013)
wave one gold
protaper next
reciproc blue
what is the standard taper
0.02
describe the taper on a taper instrument
uniform taper
what shape is non taper instrument
cylindrical
what is variable taper
more than one taper in working part
what part of the endodontic instrument is the cutting surface?
working part
what part of the endodontic instrument is the part that fits in the handpiece?
shank
what part of the endodontic instrument is from the tip to the handle/ shank?
operative part
what type of protaper files have a non active tip?
protaper universal
what type of protaper file has an active tip?
protaper retreatment
what do you call the cutting angle?
effective rake angle
what is stiffer: NiTi or SS?
SS
what is more flexible: NiTi or SS?
NiTi
how are SS Hedstrom files manufactured?
microgrinding
how are SS Kfiles/ reamers manufactured?
from raw ss wire. ground then twisted counter-clockwise
what is cheaper: ss or NiTi?
SS
describe memory shape
the file keeps martensitic phase when stress causes permanent deformation
if heated again, it will return to original austenitic phase
what is more brittle: martensitic or austenitic?
martensitic
what has a higher modulus of elasticity: austenitic or martensitic?
austenitic
how does austenite transform to martensite?
stress or heat
explain superelasticity of NiTi files
file changes from austenitic to martensitic when inserted into canal
as soon as it is removed from the canal it returns to austenitic
explain memory shape
if the temperature that the file is under is stable for the martensitic phase, the stress causes permanent transformation
the file would need to be heated again to return to an austenitic phase
