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Nickel titanium instruments for RC Flashcards

1
Q

What are files traditionally made from?

A

Made from SS

These follow a standard shape ISO

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2
Q

What is a taper?

A

The amount by which the diameter of an instrument increases from tip to handle

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3
Q

What is the set taper of traditional files?

A

2% - from each mm from the tip, the diameter of the file increases by 0.2mm

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4
Q

How long are the cutting flutes of all traditional files?

A

16mm

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5
Q

What are K-files? How are they formed?

A

Created by twisting wire to produce cutting flutes

Can be square or triangular in cross-section - get different properties

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6
Q

what are flexible k-files?

What are they made from?

A

Similar to K-files but their cross-sectional design enables them to be more flexible
SS or NiTi

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7
Q

What are Hedstrom files? How are they made?

A

Made by grinding a tapered blank
Round in cross-section with a series of cones with cutting edges
Very aggressive
Like a series of cones, aggressive, good for removing and filing dentine

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8
Q

What are the 2 ways traditional files are used

A

Watchwind-pull 30degree each way followed by a pulling action
Balanced force - 60 degrees clockwise followed by 120 degrees anti-clockwise with apical pressure

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9
Q

What is watch-winding used for?

A

Negotiating the canal and preparing the apical 1/3

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10
Q

What does the balanced force allow?

A

Fractures off dentine which have become lodged in the flutes, useful for preparing the apical 1/3

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11
Q

Why do we use traditional files? What are they used to do?

A

Used effectively to produce satisfactory canal shaping during chemomechanical canal prep
Used to negotiate canals and produce a glide-path

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12
Q

What are the disadvantages of SS files?

A

Have the tendancy to produce satisfactory canal shapes which are narrow so no irrigant gets to the apical 1/3
Become increasingly inflexible in the larger size SS
Root canals are rarely an 02 taper
The traditional prep techniques are use lots of instruments
Must be used in a reciprocating fashion
The push-pull action has the tendency to create ledges - this action also pushes debris into the canal

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13
Q

What is NiTi?

What does it allow?

A

Super-elastic metal alloy
This provides enhanced flexibility and shape
file follows the shape of the canal better - files produced with greater-taper while still retaining elasticity

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14
Q

What is elastic deformation?

A

Bend significantly and back to the original shape with no problem

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15
Q

What is plastic deformation?

A

Exceed the flexibility, wont go back to the original shape

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16
Q

Elastic modulus:

A

Exceed the elastic memory -> plastic deformation -> fracture

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17
Q

What are the 2 forms NiTi exists in?

A

Martensite and Austenite

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18
Q

What causes NiTi to be so flexible?

What does this mean?

A

The application of outer stress cases martensite to form
When the stress is released the martensite transforms back into austenite and the material returns to its original shape
NiTi can be strained several times more than ordinary metal alloys without plastic deformation

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19
Q

Due to the elasticity of NiTi, what does it allow?

A

due to the elasticity, and connection between diameter and stiffness NiTi files with 2-6x taper are possible

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20
Q

How are NiTi files designed to be used?

A

In continuous motion - wont fracture prematurely

21
Q

Why are NiTi files more expensive?

A

They cannot be twisted to shape, therefore have to be machinesd - this increases the cost

22
Q

What are the size and shape of the tips on NiTi files?

A

Will conform to ISO standard

Tips are non-cutting - allows the files to remain centred

23
Q

What is one of the main differences between NiTi and SS?

A

The presence or not of radial lands
Some systems dont have radial lands and are more aggressive, with sharp cutting edges
With radial lands makes them less aggressive, cuts less aggressively into dentine

24
Q

What is a radial land?

A

a flat area which prevents the file from locking into dentine - cutting occurs through a planing action

25
What is the rake?
The angle between the leading edge of the cutting tool and the surface being cut The rake angle can be negative neutral or positive
26
What is the rake angle of traditional endodontic instruments?
Slightly negative rake angle
27
What is the rake angle of NiTi instruments?
Sightly negative or neutral rake angle
28
What does the presence of slight grooves in the NiTi files allow? but what do they also produce more of?
efficient removal of debris from the root canal studies show that NiTi (rotary) systems are more efficient at removing debris but they do produce a thicker smear layer in the apical 1/3
29
How do you use NiTi files in practice
proper staight line access should initially be achieved The files are for canal enlargement not canal negotiation (K and SS provide the glide path) Use a crown-down technique if the canal is large enough and there is plenty of space, a glide path is already present and working length can be established straight away without coronal 2/3 opening
30
What is the crown down technique when using NiTi files?
Hand files used to create a glide path up to a minimum of size 15, ideally size 20 K-file at 2/3 of working length Shapers used to open the canal up to this length Establish the working length Shapers then finishers used to prepare the canal to full working length Apex is gauged to determine size of final file
31
What shape do NiTi files produce traditionally?
Initially, NiTi file systems used a variety of files with different taper after coronal access and creation of a glide path the different files were used to create a gradually tapering prep, with a wider taper coronally and decreasing taper towards the apex
32
What shape can the more recent NiTi files produce? | 'varied taper' concept?
files increase in taper and widen out Files no longer had one set taper, but varied in the amount of taper, starting off in the tip of the file and gradually increasing towards the shaft upside down Eiffel tower
33
What can multi-tapered instruments produce?
A canal prep with varying amounts of taper, but using fewer files
34
What does ProTaper use?
progressively tapered files Triangular cross-section It has an active cutting blade It has a blunt tip to help the file remain centred in the canal
35
In ProTaper what are the 3 shapers? and the 3 finishers?
3 shapers: SX (9 increasingly larger tapers 3.5%-19% amd 2% fixed), S1 (12 tapers 2%-11%), S2 (9 tapers 4%-11.5%)
36
What do the shaping files do?
SX, S1, S2 Shape the coronal and middle 1/3 of the canal Use after created the glide path S1 prepares the top coronal 1/3 of the root S2 prepares the mid 1/3 of the root No done the coronal 2/3
37
What do the finishing files do?
F1,2,3,4,5 | Shape the apical part of the canal
38
What is the order for using ProTaper?
SX (widens coronal), S1 (0.17mm), S2 (0.2mm), F1 (0.2mm), F2 (0.25mm), F3 (0.3mm)
39
What are contra-indications for rotary (X-Smart machine)
``` Tight or sclerosed canals - spend time finding good glide path using SS files Very curved canals S-shaped canals Apical hooks Canals with sharp elbows If glide path cannot be formed ```
40
what are the safety features of X-Smart?
precise and controlled speed | Torque control and autoreverse - reduce risk of fracture
41
What are the ergonomic features of X-smart
No foot pedal | Works on batteried micro-head (access)
42
What are the advantages of NiTi techniques?
``` Less canal transportation Flexible - better at preparing curved canals Good 'deep shape' Less debris extrusion Faster than traditional Few files used More predictable results ```
43
What are the disadvantages of NiTi?
Torsional failure caused by unwinding of the file - as a result of too much apical force during instrumentation Flexural fatigue - repeated flexing usually from overly curved canals Torsional failures more common than flextural failures
44
What are the precautions when using NiTi
``` Always have a glide path Work instruments to light resistance and never force them Light 'pecking' action Do not engage in tight curves Discard when signs of stress occur ```
45
What are the different newer developments?
M-wire Single-file technique Reciprocating action
46
What is M-wire? | What are its properties
Propietary thermomechanical treatment Lower elastic modulus and therefore more flexibility Higher fatigue resistance due to more superlastic behaviour This wire more flexible and fatigue resistant than those with conventially processed NiTi wires
47
What is the single file technique?
Due to concerns with cost of files and decontamination a single file system was developed Study which showed successful outcomes with the use of protaper F2 file only Used M-wire to reduce risk of distortion and fracture Can reduce shaping of canal time by up to 50%
48
What is reciprocating action?
Systems which use reciprocating action rather than continuous 360 degree action Reciprocating is a clockwise motion (144 degrees) followed by an anti-clockwise (72degrees) This reduced risk of distortion and fracture WaveOne uses one file with a choice of 3 depending on size of canal - canbe aggressive

APD (9 decks)

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