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Module 5 > Dental materials: Stainless steel + NiTi > Flashcards

Dental materials: Stainless steel + NiTi Flashcards

1
Q

Why are endodontic files single use?

A
  • swarf may harbour CJD (Creutzfeldt-Jakob disease)
  • minimises risk of fracture through work hardening
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2
Q

What is stainless steel an alloy of?

A

iron + carbon (steel)

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3
Q

What is added to stainless steel at manufacture?

A

chromium
may also add Ni to help corrosion + strength

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4
Q

What is the effect of adding chromium to stainless steel?

A

forms CrO2-> prevents rusting by passivating effect

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5
Q

What types of heat treatment can be applied to stainless steel?

A

-Tempering
-Heating
-Quenching

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6
Q

What is the temp range for tempering?

A

200-400

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7
Q

What are the drawbacks of SS files?

A

lack of resilience
no shape memory

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8
Q

What are the benefits of NiTi over SS?

A

softer
not heat treatable
lower modulus of elasticity
greater strenght
tougher
greater resilience
shape memory
superelasticity

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9
Q

What gives NitTi its properties?

A

changes in crystal structure

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10
Q

Describe austenitic properties

A

Hexagonal lattice
less brittle
higher modulus of elasticity

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11
Q

Describe martensitic properties

A

Body centred cubic lattice
more brittle
lower modulus of elasticity

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12
Q

Is SS or NiTi more efficient at cutting + why?

A

SS

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13
Q

Can NiTi files be twisted?

A

NO
superelasticity- so cannot be twisted unlike SS

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14
Q

What is the effect of ionic implant of boron?

A

Increased surface hardness

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15
Q

What is the benefit of thermal nitridation

A

increased wear resistance

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16
Q

What is the benefit of physical vapour deposition of TiN?

A

increased cutting ability + resistancce to NaOCl in repeat sterilisation

17
Q

What happens when NiTi corrodes?

A

releases Ti

18
Q

What can sterilisation lead to?

A

corrosion

19
Q

Which is harder in NiTi files, the core or cutting edges?

A

core

20
Q

what does heat treatment affect?

A

grain struccture

21
Q

What does the radial land do in an endo file?

A

cuts
number of these increases friction

22
Q

What does the angle/rake do in an endo file?

A

directs debris
affects cutting ability

Module 5 (6 decks)

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