Biomechanics and Biomaterials Flashcards
A good wetting material will have what contact angle?
Low contact angle; approaching 0
A poor wetting material will have what contact angle?
High contact angle; approaching 180
Are good wetting agents typically hydrophilic or hydrophobic?
Hydrophilic
Hydrophilic chemicals will wet what kind of surfaces?
Hydrophilic
What are four important aspects of surface wetting?
Important anytime two different materials come into contact; important in impression materials; important in adhesives; and important in bacterial adhesion
What is primary bonding affected by?
Generally affected by chemical and electro chemical reactions
What is secondary bonding affected by?
Generally affected by processes such as adsorption (onto) and absorption (into)
Chemical properties of a material are those that involve changes in what?
The primary and secondary bonding of the material
What is corrosion?
The spontaneous destructive oxidation of metals
What metals do not corrode?
Gold, platinum, and palladium
What does active metal corrosion lead to?
Destruction (Gamma 2)
What does passive metal corrosion lead to?
Produces a film that prevents further corrosion (Titanium implants)
In active electrochemical corrosion what is the anode?
The corroding metal
In active electrochemical corrosion what is the cathode?
A different metal (passive-supplied electrons to solution)
What are the four types of corrosion?
Galvanic, structure selective, crevice, stress
How does the chemical dissolution of ceramics happen?
Normally occurs through dissolution of oxides created by hydrogen bonding effects of water in local areas of high acidity
What are the two ways that polymers are affected?
Absorption of water into polymers (secondary bonds), and hydrolytic degradation and release of components (primary bonds)
When polymers absorb water what is the physical affect?
Dimensional change
What are the four major material properties?
Physical, chemical, biological, and mechanical
Biologic properties are interrelated with what two things?
Degradation properties, and polymerization process or processing
What do the mechanical properties of a material describe?
How a material responds to loads (forces)
What are the three single dimension forces?
Compression, tension, and shear
What are the three combination forces?
Torsion, flexion, and diametral compression
What is resilience?
The amount of force that can be applied before deformation occurs
What is toughness?
The amount of force that can be applied before failure or fracture occurs
Hardness is a relative measure of what?
Plastic deformation
Fracture toughness measures what?
A materials resistance to crack propagation
What is creep?
(Strain relaxation); deformation over time in response to low constant stress
What is stress relaxation?
Deformation over time in response to low constant strain
What are the normal biting forces?
150-550N (35-125lbs)
What are max biting forces?
200-2440N (45-550lbs)
What is the molar biting force?
500N
