5. Instrumentation Flashcards
What anatomical challenges does the root canal system pose?
The number, length, curvature and diameter of canals can vary greatly.
What are the 5 types of motion you can use with instruments?
Filing Reaming Watch-winding Balanced forced motion Envelope of motion
What is watch-winding?
Backwards and forwards osscilation of 30-60 degrees using light apical pressure.
Effective with K-files.
Useful for passing small files through canals.
What is the aim of instrumentation?
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
What are barbed broaches used for?
Extirpating not enlarging!
They will engage the pulp tissue and remove it from the canal.
What length is the cutting flute of ISO instruments?
16mm
What are H files used for?
Removing GP or fractured instruments in retreat meant cases.
What shape is the H files tip?
Tear drop
What shape is the reamers tip?
Triangular
What shape is the tip of a K-file?
Square
What are the drawbacks of conventional hand preparation techniques?
Mishaps - ledges, canal blockade, zipping of foramen
Debris extrusion with filing motion
Time consuming
Curved canals are difficult
What can cause a blockage in the root canal and what problems does it present?
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.
What is a ledge and how is it caused?
A ledge is internal transportation of the canal.
Occurs when working short of length.
What problems does apical transportation present?
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
What problems does zipping cause?
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
Why does zipping occur?
Occurs as a result of the tendency of the instrument to straighten inside a curved canal.
How would you diagnose root perforation?
Persistent bleeding into canal
Multiple radiographs
Electronic apex locators
Dental operating microscope
What factors does the prognosis of a perforated tooth depend on?
Location Time elapsed Size Periodontal irritation Material used for repair
What are the advantages of NiTi vs SS?
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
What are the disadvantages of NiTi?
Instrument fracture
Expense
Access can be difficult in posterior teeth
Unsuitable for canals with complex anatomy
What are the benefits of using rotary files?
Mimics manual movement
Reduces risk associated with continuously rotating a file through canal curvatures
