Week 8 Flashcards
What are 4 biomedical applications of metals outside of dentistry?
- orthopedic implants
- fracture management devices
- stents
- spinal cage
What are 5 biomedical applications of metals in dentistry?
- brackets
- dental implants
- tools
- RPD
- restorations - amalgam
Where are metals found in the periodic table?
Any of several solid mineral elements that are malleable under heat or pressure and can conduct heat/electricity
metal
What are 4 examples of metals?
- iron
- gold
- silver
- copper
Why don’t pure metals have practical use in the industry?
low properties and expensive fabrication
the mix of two or more substances where at least one of them is a metal
alloy
What two things make up steel?
- iron
- carbon
What two things make up amalgam?
- mercury
- silver
What are the differences between metals and alloys?
What type of structure do metals have?
crystalline
True or false: metals are arranged in very compact and orderly patterns
true
What are the three main arrangement of atoms in metals?
- cubic body centered
- cubic face centered
- hexagonal
What are the five main methods of metal product manufacture?
- machining
- metal casting
- forging
- pressing
- 3D printing
What influences final properties of metals?
fabrication processes
What are the 6 post-processing (heat treatment) fabrication methods?
- annealing
- quenching
- agin
- stress
- relieving
- tempering
How are metal parts fabricated?
What 5 characteristics make up the ideal metallic biomaterial?
- high corrosion resistance
- biocompatibility
- osseo-integration
- high wear resistance
- suitable mechanical properties
What is wolf’s law of bone remodelling?
a result of removal of stress from the bone due to an implant
osteopenia
Ostepenia is an example of resorption or remodelling?
resorption
Who usually is affected by osteopenia?
astronauts
a biomechanical phenomenon causing adaptive changes in bone strength and stiffness around metallic implants, which potentially lead to implant loosening
stress shielding
Describe bone loss in Gruen zones
composite = too weak and could break (remove/resorb bone due to low stress)
titanium = just enough stress to both resorb and make bone (ideal substance for implants)
co-cr-mo = too much stress, bone continually added and too stiff
What are 6 common metallic biomaterials?
What is the gold standard in implant materials?
titanium (Ti) and Ti-alloys
What are the two characteristics of Ti and Ti-Alloys?
- light weight (2x lower than stainless steel and Co-Cr alloy)
- suitable mechanical properties for load-bearing
What is commercially pure Ti or cp-Ti?
Describe the mechanical properties of cp-Ti and how they change with grades
What are the Ti phases?
Ti is manufactured via controlled machining which comprises what 3 things?
- lathing
- threading
- milling
Why is casting Ti alloys difficult?
- high melting points (1700 C)
- Ni absorption
Describe the classification of Ti-alloys according to ASTM
What three things do Ti alloys (Ti6Al4V) consist of?
What are the Ti6AL4V properties?
When is an implant osseointegrated?
when virtually no mobility in the bone is clinically detectable
How should the interface be between the alloy and the bone of an implant?
direct with no intervening fibrous tissue
Bony tissue grows to within _____ A of the implant surface
100
Why is Ti alloy one of the most biocompatible materials?
it has excellent corrosion resistance
What is the corrosion resistance of a Ti alloy due to?
formation of inert oxide layer
In a Ti-alloy implant, where does bone grow?
adjacent to oxide surface
What is the main reason for excellent biocompatibility of Ti?
low level of charge transfer
The oxide layer is self-healing, what does this mean?
if the surface is scratched it repassivates instantaneously
How does the oxide layer form?
titanium spontaneously forms a oxide surface on
exposure to air or physiologic saline environment
What makes up stainless steel?
What is corrosion resistance attributed to?
formation of chromium oxide layer (Cr2O3)
**more quantity of Cr, better corrosion resistance
The (less/more) quantity of Cr, the better the corrosion resistance
more
What is the classification of stainless steel?
What are the 4 characteristics of martensitic SS?
What are the two characteristics of ferritic SS?
- manufacturing medical devices
- handles for instruments and medical guide pins
What are 4 characteristics of austenitic SS?
- excellent cryogenic properties
- high temperature strength
- oxidation resistance
- formability
What 4 things does SS 316L consist of?
- Iron 60-65%
- Chromium (17-20%)
- Nickel (12-14%)
- Small amounts of Mo, Ni, C, P, Si, F
What does the L in 316L stand for?
low carbon content (<0.030%)
Why is it important to have low carbon content?
for excellent corrosion resistance (prevent carbide accumulation)
What 3 things is SS 316L primarily used for?
- coronary stents
- orthopedic implants
- fracture fixation devices
What is the drawback of SS 316L?
release of certain metal ions that may lead to some serious disease (Fe, Ni, Cr)
What are the four common variations of cobalt based alloys (co-cr alloys)?
What has higher corrosion resistance? stainless steel or cobalt-based alloys?
cobalt based alloys b/c they form a Cr2O3 oxide layer
Describe the roles of alloying elements
What are two issues associated with cobalt-based alloys?
- stress shielding
- metal toxicity
Co alloys are generally superior to stainless steels in terms of what 3 things?
- corrosion
- fatigue
- wear
What remains the most popular metallic implant for joint bearing systems?
Wrought Co-Cr-Mo alloys
What is an outstanding property of nitinol?
What does nitinol consist of?
What are two examples of smart applications?
- self expanding stents
- smart brackets
True or false: Biocompatibility remains controversial for Ni-Ti
True
