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Flashcards in metallic instruments and implants Deck (72):
1

What are the 3 main categories of stainless steel instruments?

martensitic, precipitation hardenable, austenitic

2

martensitic stainless steel has ______ corrosion resistance and is ______ magnetic.

moderate; highly

3

the martensitic compositions contain what percentage chromium? describe their carbon content.

12 to 18%; a medium to high carbon content, and other minor elements

4

Common  types of martensitic alloys of the 400 series of stainless steel  include 420A, 431, and 440B. How does the nomenclature relate to it composition?

the higher three digit 4XX number indicates a higher chromium range for a given alloy (440 > 431 > 420).
the suffix letters A,B, or C define an increasing carbon range for a given alloy (420C > 420B > 420A).

5

T/F: martensitic stainless steel alloys are ideal for cutting instruments and for use in noncutting tools.

True; . Martensitic alloys are very hard and resistant to wear, which makes  them ideal for cutting instruments (such as drills, taps, countersinks, reamers, chisels, and bone-cutting forceps) and for use in  noncutting tools (such as screwdrivers and wrenches).

6

What is heat treating?

 Heat treating is a hardening process that transforms the microstructure with temperatures in the range of 930° to 1150° C, followed by a controlled  quench in air or a liquid. The hardened alloy is then tempered 
at an intermediate temperature of 150° to 370° C to develop  the final optimal properties

7

how does increasing the tempering temperature change the hardness of a given martensitic alloy?

the hardness decreases as the tempering temperature increases.

8

T/F: Precipitation hardenable (PH) stainless steels contain substantial amounts of chromium, nickel, and copper, plus controlled  levels of secondary elements.

True;  A commonly used PHgrade alloy contains 17% chromium plus 4% nickel (17-4PH)  and is identified as Type 630.

9

T/F: The PH grades contain a high carbon content, so edge  retention and wear resistance are superior when compared with  the 400 series martensitic compositions.

False; The PH grades do not contain a high carbon content, so edge  retention and wear resistance are inferior when compared with  the 400 series martensitic compositions

10

T/F:  PH stainless steels are used for a variety of  noncutting instruments that require a moderate hardness level.

True

11

The term __________ describes the type of microstructure associated with 300 series stainless steel, which is ________  magnetic and has ________ corrosion resistance

austenitic; slightly; excellent

12

A commonly used __________ alloy contains 17% chromium plus 4% nickel (17-4PH)  and is identified as Type 630.

precipitation hardenable alloy

13

What are the usual composition ranges of chromium and nickel in austenitic alloys?

16% to 18% chromium (similar to PH alloys); 8% to 10 % nickel (c.f. ~ 4% in PH alloys)

14

T/F: In austenitic alloys, the low carbon grades, such as 304L meet a compositional requirement of a maximum  of  0.03%  carbon.

True; (L indicates  low carbon)

15

 The austenitic  alloys 316 and 316L contain what percent molybdenum?

2% to 3%

16

T/F:  The austenitic  alloys, except for 316 and 316L, which contain 2% to 3% molybdenum, also become slightly magnetic as the amount of coldwork increases. 

True

17

T/F: the 300 series stainless steels have outstanding cutting and wear properties.

False; the 300 series are austenitic alloys and have poor cutting and wear properties because of the low carbon content.

18

T/F: Austenitic alloys can be strengthened by cold working, however they can become slightly magnetic as the amount of cold-working increases.

True; The  300  series  stainless  steels  may  be  strengthened  by  cold  working,  but  they  do  not  have  outstanding  cutting  or  wear  properties because of the low carbon content. The austenitic  alloys, except for 316 and 316L, which contain 2% to 3% molybdenum, also become slightly magnetic as the amount of cold work increases. Some of the austenitic stainless steels can be  cold-worked to a very high tensile strength and may be used for  some noncutting applications including drill guides, clamps,  hollow sleeves, springs, and washers

19

Aluminum _____ are frequently used for bone plate/rod templates.  They are ____ in strength,  highly _______ (malleable), nonmagnetic, and lightweight

templates; low; ductile;  

*Aluminum grade 1100 meets a minimum  aluminum content of 99% and is supplied in the soft annealed  condition (O temper).

20

T/F: Pure aluminum has more strength and less ductility when  compared with aluminum alloys.

False; Aluminum alloys have more strength and less ductility when  compared with pure aluminum

21

T/F: Aluminum alloys nonmagnetic and lightweight. They are  frequently used for depth gages, intramedullary (IM) nail-insertion instruments, hollow external-fixation rings, graphic case modules, and  screw  racks. 

True

22

T/F: Aluminum  contact  with  strong  alkaline  cleaners  must  be  avoided to prevent aggressive chemical attack.

True; Chemical  cleaning  solutions  containing  chlorine,  iodine, or certain metal salts may attack the anodized coating.

23

Implant quality 316L stainless steel is an iron-based stainless composition, aka wrought 18% chromium-14% nickel-2.5% molybdenum implant alloy. What qualities do the chromium, nickel, and molybdenum lend to the compound? What is its carbon content?

Chromium provides corrosion resistance; nickel lends greater microstructural stability; molybdenum improves resistance to pitting and crevice corrosion. This alloy has a low carbon content (maximum, 0.03% carbon) which improves resistance to intergranular corrosion.

24

Can you use a titanium plate with stainless steel screws?

No;  For  multicomponent devices, such as plates and screws, it is not  advisable to mix stainless steel and titanium implants because  an accelerated form of corrosion, known as galvanic corrosion,  can occur.

25

T/F: The  alloy  may  also  be  supplied  in  the  cold-worked  or  moderate-strength condition to resist the stress loading encountered by bone plates and bone screws. Cold-working refers to a  metalworking operation that permanently deforms the material  at room temperature to increase the strength, usually by reducing the cross-sectional area by drawing or rolling

True

26

The excellent corrosion resistance of stainless steel is primarily a result of a _________ _____ film, known as the ________ layer,  which is present on the surface. 

Chromium oxide; passive

27

T/F:  Chemical passivation in nitric  acid  is  a  commonly  used  method  of  surface  finishing  for stainless steel implants.

True;  Immersion in 20 to 45 volume-percent  nitric acid passivation solution removes surface contaminants,  such as cutting tool transfer films, oxide from heat treatment,  imbedded particles, and burned-in lubricants. The passivation  process restores maximum corrosion resistance but does not  affect part dimensions.

28

 Immersion in 20 to 45 volume-percent ______ _______ passivation solution removes surface contaminants,  such as cutting tool transfer films, oxide from heat treatment,  imbedded particles, and burned-in lubricants. The passivation  process restores maximum corrosion resistance but does not  affect part dimensions.

nitric acid

29

____________ is a surface treatment that consists of  applying an electric current to an implant immersed in a specially formulated chemical solution under specified conditions    of  time  and  voltage.

Electropolishing

30

T/F: Electropolishing removes  a  microscopic  amount of metal, decreases the surface roughness of the implant,  provides a low coefficient of friction, improves corrosion resistance, and creates a chemically passivated surface.

True

31

T/F: repeated steam autoclaving will disrupt the passive film and  alter the mechanical properties of stainless steel implants. 

False; repeated steam autoclaving will not disrupt the passive film or  alter the mechanical properties of stainless steel implants. 

32

What does shot-peening  before  electropolishing do to stainless steel implants?

improves fatigue strength; In shot-peening the  implant  surface is subjected to high-velocity impaction by metallic or  ceramic particles under well-defined conditions. Shot-peening  produces a roughened surface with increased residual compressive stress for enhanced fatigue life.

33

T/F: Implant quality stainless  steel is completely nonmagnetic in all conditions, and implants  will not exhibit torsional movement or displacement during MR  scans.

True

34

T/F: Signal artifacts may obscure complete MR visualization in the  vicinity of the stainless implant. 

True

35

T/F: The 15% nickel content may provoke a metal sensitivity reaction and is responsible for about 90% of the metal allergies that  are clinically observed in people.

True

36

Commercially pure (CP) titanium, also known as unalloyed titanium, is available in five implant compositions designated Ti  Grade 1 ELI, 1, 2, 3, and 4. What does ELI stand for? how do the grade changes affect the strength and ductility?

ELI = extra-low interstitial grade (it has  the lowest content of nitrogen, carbon, iron, and oxygen).

 The strength increases and the  ductility decreases as the grade changes from the lowest designation (grade 1 ELI) to the highest designation (grade 4).

37

T/F: Stainless steel has better biocompatibility than CP titanium.

False; CP titanium has better biocompatibility than stainless steel and typically  contains  less  than  0.05%  nickel. Unalloyed  titanium  implants will not cause metal allergy reactions and are recommended for humans in situations where metal sensitivity is  preoperatively verified or where 316 L stainless steel implants  have provoked an allergic response.

38

T/F: Titanium's unique biocompatibility properties include soft tissue and bone adhesion to the implant  surface,   possibly resulting in less  bacterial  colonization  and  reduced infection.

True

39

T/F:  Tissue adjacent to pure titanium implants  becomes well vascularized, with less tendency toward capsule  formation. 

True

40

What is a major disadvantage associated with titanium implants?

 titanium implant removal may be difficult, especially for well-osseointegrated implants

41

T/F: The pitting  and crevice corrosion resistance of titanium is inferior to stainless steel. 

False; The pitting  and crevice corrosion resistance of titanium is superior to stainless steel. 

42

T/F:  Titanium implant materials have a lower density,  have a lower modulus of elasticity, and provide significantly less  MR artifact when compared to stainless steel.

True

43

How do the densities and weights compare between stainless steel and titanium implants?

 The density of  titanium is 57% of the density of stainless steel and represents a weight reduction of nearly 50% when implants of similar  dimensions are compared.

44

The _________ __ __________ is a constant physical property that  describes the stress per unit strain in the elastic region. 

modulus of elasticity; A material with a high modulus of elasticity will transfer less stress  from the implant to the bone.

45

 A material with a high modulus of elasticity will transfer less stress  from the implant to the bone. This may produce a condition  known as ________ __________, which is not ideal because bone must  be adequately stressed to consolidate properly during the bone healing stage.

stress shielding

46

How does the modulus of elasticity compare between titanium and stainless steel implants?

 The modulus of elasticity of titanium is about  55% of stainless steel, and the low modulus is desirable because  of increased stress transfer. 

47

T/F:  The anodizing treatment for titanium is different  from the electrolytic anodizing treatment used for aluminum.  The titanium implants are immersed in a chemical solution and  a known electrical voltage is applied for a specified time.

True

48

T/F:  The titanium anodizing process is capable of  producing a variety of colors that permit the design of colorcoded implant systems.

True;  Visible  light diffraction within the oxide film creates a distinct color,  which depends on the thickness of the oxide film. No pigments or organic coloring agents are present in the anodized  titanium film. 

49

T/F: Multiple steam sterilization cycles will significantly change the appearance of  anodized titanium implants. 

False; Multiple steam sterilization cycles will not significantly change the appearance of  anodized titanium implants. However, fingerprint contamination from skin contact should be avoided when handling the  implants between autoclave cycles. Gloved handling of anodized titanium implants prevents the discoloration of isolated  areas during steam autoclaving.

50

In regard to titanium alloys, what does "ELI" indicate?

The ELI designation denotes lower oxygen content and lower  hydrogen content

51

What are common titanium alloys (composition)?

Titanium-6 aluminum-4 vanadium alloys containing approximately  6% aluminum and 4% vanadium;

titanium, 6% aluminum, and 7%  niobium
titanium-15 molybdenum

52

Titanium  alloys  have ______  tensile  strength  capability,  _______ ductility, ______ modulus of elasticity, and equivalent  density when compared to CP titanium.

higher; lower; similar;

53

Define notch sensitivity.

 Notch sensitivity is a term that describes the relative effect that local irregularities or stress raisers have on mechanical  properties.

54

T/F: The  notch  sensitivity  resistance  of  implant quality stainless steel is similar to unalloyed titanium and is  somewhat better than conventional titanium alloys.

True

55

_______ alloys are used primarily for prosthetic implants,  such  as  total  hips,  total  knees,  and  total  disc  replacement.

Cobalt-base alloys

56

Co-28Cr-6Mo is the predominant Cobalt-base alloy that is fabricated for  joint replacement applications. The nickel content of this alloy  is typically less than what?

less than 0.5%

57

This alloy may be hot forged  into complex shapes, the tensile strength can exceed 1172 MPa,  and the wear resistance is outstanding.

Cobalt-base alloy

58

Which has better corrosion resistance (cobalt-base alloys, stainless steel, titanium)?

Titanium > cobalt-base alloy > stainless steel

59

Unique properties of  cobalt-base alloys include a high modulus of elasticity, which  may be ___% ______ than stainless steel. 

25% greater

60

_____________ increases  the strength of cobalt-base alloys, and thermal aging heat treatments can significantly _______ the yield strength and ultimate  tensile strength. 

Cold-working; increase

61

T/F: Certain cobalt base alloys contain greater than  10% nickel, which may provoke a nickel allergy reaction.

True

62

T/F:  The  excellent corrosion resistance of the cobalt-base alloys is predominantly the result of the chromium content, which typically  exceeds  19%.

True

63

T/F: Chromium  and  cobalt  are  considered  metal-  sensitizing agents but the clinical incidence of sensitivity reactions are relatively rare when compared with nickel.

True

64

T/F: Fatigue is a phenomenon leading to fracture under repeated or  fluctuating stresses having a maximum value less than the ultimate tensile strength of the material.

True; The fatigue loads are well  below the level that normally would be required to cause fracture within a single load cycle. The fatigue cycle is the time  interval  during  which  the  stress  is  regularly  repeated. 

65

One  common measure of the fatigue properties is known as the ____________ ________, which is the maximum stress below which a  material can presumably endure an infinite number of stress  cycles.

endurance limit

66

What is an S-N curve?

A common method of expressing the fatigue properties of a  material is known as the S-N curve. The S-N curve is a best-fit  plot of the individual test values, where S refers to the applied  cyclic stress and N is the number of cycles required to fracture  the test specimen or to achieve runout.

67

Define runout.

 Runout is defined as the  maximum cyclic stress that does not create fatigue fracture at a  predetermined number of cycles (usually 10^6 cycles or greater).

68

In this type of testing, a bone plate is  placed in a four-point bending fixture and oriented in a manner  that mimics clinical bridging of a fracture site. The bone plate  is subjected to a constant frequency cyclic load in four-point  bending.  The  test  method  establishes  a  uniform  four-point  _____ _______ ______ to characterize and compare the fatigue  performance of different plate designs. 

 bending fatigue test

69

T/F: When comparing bending fatigue curves for 3.5 mm DCP and 3.5 mm LC-DCP,  the  bone plate fatigue curves reveal that the DCP has increased  resistance to maximum compressive fatigue loads when compared to LC-DCP in the low load–high cycle region (greater  than 10^5 cycles).

True;  Maximum runout load for the DCP (n = 4)  was 323 N, whereas the maximum runout load for the LC-DCP  (n = 5) occurred at 268 N.

70

T/F: The endurance limit for 316L stainless steel and CP titanium  increases  as  the  percentage  of  cold-work  increases.

True

71

 T/F: Titanium alloys exhibit a greater 0.2%  yield strength when compared with CP titanium, and this factor  is primarily responsible for the superior fatigue properties of  titanium alloys when compared with CP titanium.

True

72

 Many fracture-fixation implants require a certain balance  between ________ and ________ (i.e., ability to contour a bone  plate) so that specifying the highest attainable tensile strength  is not always desirable. 

Strength; ductility