Pathways

Question 1

Classification of Instruments used for cleaning and shaping the root canal system; Group 1 is?

Answer 1

Manually operated instruments, such as barbed broaches and K-type and H-type instruments

Question 2

Classification of instruments used for cleaning and shaping the root canal system; Group 2 is?

Answer 2

Low speed instruments with a latch type attachment. Ex. gates Glidden burs and Peeso reamers. Usually used in coronal portion, not curvature.

Question 3

Classification of instruments used for cleaning and shaping the root canal space. What is group 3?

Answer 3

Engine-driven nickel-titanium rotary instruments. They consist of a rotating blade that can safely be operated in curved root canals.

Question 4

Classification of instruments used for cleaning and shaping the root canal space. What is group 4?

Answer 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.

Question 5

Classification of instruments used for cleaning and shaping the root canal space. What is group 5?

Answer 5

Engine driven reciprocating instruments

Question 6

Classification of instruments used for cleaning and shaping the root canal space. What is group 6?

Answer 6

Ultrasonic instruments

Question 7

What is the standard taper of ISO files?

Answer 7

0.02 mm per millimeter

Question 8

What is the length of the working part of an ISO file?

Answer 8

16mm

Question 9

What is the phrase used to remember the ISO file sizes?

Answer 9

When you reach black go back. 
White 15
Yellow 20
Red 25
Blue 30
Green 35
Black 40

Question 10

What is the extension of an access cavity into the coronal most portion of the root canal called?

Answer 10

Coronal flaring

Uses gates gliddens and other NiTi instruments

Question 11

What does modulus of elasticity refer to?

Answer 11

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

Question 12

What is super flexibility or superelasticity?

Answer 12

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

Question 13

Nickel titanium’s thermodynamic properties are due to its ability to phase change. What are the two phases?

Answer 13

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

Question 14

What causes the nickel titanium instrument to go from A-phase to M-phase?

Answer 14

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

Question 15

What is tensile strength?

Answer 15

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.

Question 16

What is yield strength?

Answer 16

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.

Question 17

What is ultimate strength of a material?

Answer 17

The maximum stress a material can withstand

Question 18

What is breaking strength of a material?

Answer 18

The stress coordinate on the stress-strain curve at the point of rupture

Question 19

What is plastic deformation?

Answer 19

Irreversible change that remains once the applied external force has reduced or ceased

Question 20

How much strain can steel allow before plastic deformation occurs? How much can nickel titanium withstand?

Answer 20

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

Question 21

What are milling marks?

Answer 21

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.

Question 22

Why does fracture occur with nickel titanium files?

Answer 22

Either due to cyclic fatigue or torsional fracture.

Question 23

What is cyclic fatigue?

Answer 23

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

Question 24

What is torsional fracture?

Answer 24

Occurs when the instrument tip is locked within the canal while the shaft continues to rotate.

Question 25

Are larger or smaller NiTi files more prone to torsional failure? 

Answer 25

Smaller.

Larger files more prone to cyclic fatigue

Question 26

What is the original operating speed for the lightspeed system?

Answer 26

2000 RPM

Question 27

What is the “12 pecks rule”?

Answer 27

Advice that the master apical rotary file (MAR) be determined when a file requires 12 packs to reach working length. (Senia & Wildey)

Question 28

What are the main differences of the lightspeed LSX from the original LS1?

Answer 28

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

Question 29

What are the basic tenants of shaping canals?

Answer 29

Safety, effectiveness and simplicity