5. Instrumentation

Question 1

What anatomical challenges does the root canal system pose?

Answer 1

The number, length, curvature and diameter of canals can vary greatly.

Question 2

What are the 5 types of motion you can use with instruments?

Answer 2

Filing
Reaming
Watch-winding
Balanced forced motion
Envelope of motion

Question 3

What is watch-winding?

Answer 3

Backwards and forwards osscilation of 30-60 degrees using light apical pressure.
Effective with K-files.
Useful for passing small files through canals.

Question 4

What is the aim of instrumentation?

Answer 4

Remove infected hard & soft tissue
Give disinfecting irrigants access to apical space
Create space for the delivery of medicaments & obturation
Retain the integrity of the radical are structure

Question 5

What are barbed broaches used for?

Answer 5

Extirpating not enlarging!

They will engage the pulp tissue and remove it from the canal.

Question 6

What length is the cutting flute of ISO instruments?

Answer 6

16mm

Question 7

What are H files used for?

Answer 7

Removing GP or fractured instruments in retreat meant cases.

Question 8

What shape is the H files tip?

Answer 8

Tear drop

Question 9

What shape is the reamers tip?

Answer 9

Triangular

Question 10

What shape is the tip of a K-file?

Answer 10

Square

Question 11

What are the drawbacks of conventional hand preparation techniques?

Answer 11

Mishaps - ledges, canal blockade, zipping of foramen
Debris extrusion with filing motion
Time consuming
Curved canals are difficult

Question 12

What can cause a blockage in the root canal and what problems does it present?

Answer 12

Caused by dentine debris getting packed into the apical portion of the root. It can be as hard as surrounding dentine if it is packed tightly. Attempts to remove it can lead to a false canal being cut and perforation.

Question 13

What is a ledge and how is it caused?

Answer 13

A ledge is internal transportation of the canal.

Occurs when working short of length.

Question 14

What problems does apical transportation present?

Answer 14

Fails to provide resistance for packing of gutta percha
In severe cases bleeding can be a problem
Attempting to reshape can result in weakening or perforating the tooth

Question 15

What problems does zipping cause?

Answer 15

Over-enlargement along the outer side of the curvature
Under-preparation of the inner aspect at the apical end point
The main axis of the canal is transported
Results in tear-drop or hourglass shape

Question 16

Why does zipping occur?

Answer 16

Occurs as a result of the tendency of the instrument to straighten inside a curved canal.

Question 17

How would you diagnose root perforation?

Answer 17

Persistent bleeding into canal
Multiple radiographs
Electronic apex locators
Dental operating microscope

Question 18

What factors does the prognosis of a perforated tooth depend on?

Answer 18

Location
Time elapsed
Size
Periodontal irritation
Material used for repair

Question 19

What are the advantages of NiTi vs SS?

Answer 19

Increased flexibility (superelasticity) in larger sizes and tapers
Increased cutting efficiency
Safe if used appropriately
Can be more user friendly with less instruments & simple sequences

Question 20

What are the disadvantages of NiTi?

Answer 20

Instrument fracture
Expense
Access can be difficult in posterior teeth
Unsuitable for canals with complex anatomy

Question 21

What are the benefits of using rotary files?

Answer 21

Mimics manual movement

Reduces risk associated with continuously rotating a file through canal curvatures