Pathways Flashcards
Classification of Instruments used for cleaning and shaping the root canal system; Group 1 is?
Manually operated instruments, such as barbed broaches and K-type and H-type instruments
Classification of instruments used for cleaning and shaping the root canal system; Group 2 is?
Low speed instruments with a latch type attachment. Ex. gates Glidden burs and Peeso reamers. Usually used in coronal portion, not curvature.
Classification of instruments used for cleaning and shaping the root canal space. What is group 3?
Engine-driven nickel-titanium rotary instruments. They consist of a rotating blade that can safely be operated in curved root canals.
Classification of instruments used for cleaning and shaping the root canal space. What is group 4?
Engine driven instruments that adapt themselves three dimensionally to the shape of the root canal. There’s currently only includes one instrument the self adjusting file SAF from ReDent-Nova.
Classification of instruments used for cleaning and shaping the root canal space. What is group 5?
Engine driven reciprocating instruments
Classification of instruments used for cleaning and shaping the root canal space. What is group 6?
Ultrasonic instruments
What is the standard taper of ISO files?
0.02 mm per millimeter
What is the length of the working part of an ISO file?
16mm
What is the phrase used to remember the ISO file sizes?
When you reach black go back. White 15 Yellow 20 Red 25 Blue 30 Green 35 Black 40
What is the extension of an access cavity into the coronal most portion of the root canal called?
Coronal flaring
Uses gates gliddens and other NiTi instruments
What does modulus of elasticity refer to?
The inherent stiffness of a material. A high modulus of elasticity means the material has more inherent stiffness and will reach plastic or permanent deformation with stress more quickly
What is super flexibility or superelasticity?
The ability of a material to resist stress without permanent deformation. The ability to return to its original shape without showing signs of permanent deformation is described as shape memory effect
Nickel titanium’s thermodynamic properties are due to its ability to phase change. What are the two phases?
Austenite (A-phase)- parent phase, hexagonal lattice, strong & hard (still flexible)
Martensite (M-phase)- when stress occurs, like contact w the canal wall, body-centered cubic lattice, more elastic and greater tensile strength
What causes the nickel titanium instrument to go from A-phase to M-phase?
Stress during procedures or due to changes in temperature during manufacturing causes transformation. Once the stress is released the M phase transforms back to austenite
What is tensile strength?
A measurement of the force required to pull something such as a rope, wire or structural beam to the point where it breaks. The tensile strength of a material is the maximum amount of tensile stress that it can take before failure.
What is yield strength?
The stress a material can withstand without permanent deformation. This is not a sharply defined point. Yield strength is the stress which will cause a permanent deformation of 0.2% of the original dimension.
What is ultimate strength of a material?
The maximum stress a material can withstand
What is breaking strength of a material?
The stress coordinate on the stress-strain curve at the point of rupture
What is plastic deformation?
Irreversible change that remains once the applied external force has reduced or ceased
How much strain can steel allow before plastic deformation occurs? How much can nickel titanium withstand?
Steel allows 3% strain before plastic deformation. Nickel titanium can allow 8% strain. After 100 death formations the tolerance for elasticity decreases to 6% of the original strain ability
What are milling marks?
Surface irregularities and grooves produced during the traditional manufacturing of nickel titanium files. They can compromise cutting ability and lower fatigue resistance or act as stress raisers that may make the file more susceptible to fracture.
Why does fracture occur with nickel titanium files?
Either due to cyclic fatigue or torsional fracture.
What is cyclic fatigue?
When an instrument rotates in a curved canal, leading to motion induced repeated compressive and tensile stress. Product of hardening and metal fatigue, resulting in failure
What is torsional fracture?
Occurs when the instrument tip is locked within the canal while the shaft continues to rotate.
Are larger or smaller NiTi files more prone to torsional failure? 
Smaller.
Larger files more prone to cyclic fatigue
What is the original operating speed for the lightspeed system?
2000 RPM
What is the “12 pecks rule”?
Advice that the master apical rotary file (MAR) be determined when a file requires 12 packs to reach working length. (Senia & Wildey)
What are the main differences of the lightspeed LSX from the original LS1?
LSX illuminates the half sizes with only ISO numbers
The rotational speed is 2500 RPM instead of 2000
The recommended use is in a slow advancement pattern rather than pecking
The LSX blade is slightly shorter but there is a more flexible shaft
What are the basic tenants of shaping canals?
Safety, effectiveness and simplicity
