Biomechanics Flashcards
What are the goals of dental materials
longevity, function properly, aesthetics, patient satisfaction
Model of dental materials
similar to tooth structure, properties, and composition
What are the limitations of dental materials?
cannot know everything about a given material/system, have to choose parameters
Define measure (surface properties)
contact angle used to measure how liquid interacts w/ solid
Define good wetting
low contact angle
Define poor wetting
high contact angle
What are some clinical consequences of surface properties?
bonding time, cell attachment (sheer strength), hydrophilic/phobic, and surface area/roughness
What makes sealants
a slowable resin with NO filler that is clear
Is HEMA hydrophobic or hydrophilic?
possesses both
What is an advantage of hydroPHILIC primers?
low viscosity and allows for attachment to composite
Is tooth structure (dentin) hydrophobic or hydrophilic
hydrophobic
Where is surface wetting important?
anytime two different materials come in contact, impression materials, adhesives, bacterial adhesion
What does primary bonding affect?
chemical and electrochemical reactions
What does secondary bonding affect?
adsorption (onto) and absorption (into)
How are metals affected?
corrosion or spontaneous destructive oxidation
what metal do not corrode?
gold, platinum, titanum and palladium
Define active corrosion
leads to destruction via gamma 2
Define passive corrosion
production od corrive film that prevents further corrosion
Define immune corrosion
noble metals (full valence octet)
What are the components of electrochemical corrosion?
anode, cathode, circuit, and electrolights in solution
What is an anode?
corroded metal
What is a cathode
a passive supplier of electrons to solution
What are the four types of corrosion?
glavanic, structural selective, cervice (crack), stress
Define chemical dissolution
dissolution of oxides created by hydrogen bonding effect of water in local areas of high acidity
What does absorption of water affect polymers?
the secondary bonds cause 3D changes and the primary bonds of the polymer breaks piece by piece
What are the concerns of biological properties?
No adverse reaction, toxicity, and sensitivity to react/degrade
Define mechanical properties
how a material responds to loads/forces
What are the three types of single dimension forces?
Compression (push together)
Tension (pull apart)
Shear (opposing forces)
What are the three types of combination forces?
Torsion (twisting)
flexsion (tensile or bending)
Diametral compression (capable of being stretched)
What is the correlationn between stress and strain?
directly coerelated
more stress - more strain until elastic limit
Define ultimate stress
highest stress (force/area)
Define elastc modulus
Stiffness
Define plastic deformation
when a sufficient load is applied, it will cause the material to change shape but revert to the original shape
Define elastic deformation
when a sufficient load is applied,it will cause the material to change shape
Define total deformation
plastic and elastic deformation
Define stiff brittle
high stress and does not change length
Define stiff ductile
high stress and changes length
Define flexible ductile
low stress drastically changes the length
Define resilience
measures the energy absorbed by the material before deformation
Define toughness
measures the energy absorbed by a material before failure or fracture
What are mechanical events dependent on?
time and temperature
Do impressions removed fast have higher or lower deformation?
Lower
What is hardness a relative measure of?
Plastic deformation
Define fracture toughness
measures the resistance to crack propagation
What happens to mechanical properties over time?
the properties degrade, cracks & non-difficult defects accumulate, water is absorbed
Define creep
deformation over time in response to low constant stress
What happens after many cycles of low stress?
fatigue or small amounts of deformation accumulate until failure occur at low stress
True or false, the larger the number of cycles the less stress that can be applied before failure
True
What class of lever is chewing?
Class 3,
Fulcrum , effort, load
What is normal biting forces?
35-125 lbs or 150-550 N
What kind of forces are teeth subjected to when chewing?
strain through subclinical movements
What kind of forces lead to heavy wear on teeth?
abfractions or mechanical tooth loss that is not caused by decay and is often found along the gum line
What leads to microfractures of enamel rods?
cyclic tension and compression
Define microfracture
enamel loss due to mechanical or chemical forces
How is stress transferred in a tooth?
The stress causes formation in enamel, which is transferred to dentin via DEJ
Do preps weaken the tooth structure?
Yes, it takes a smaller load to break or reach critical strain
Define single cycle overload
single event that is very sudden that causes breakage
Rank the materials that can handle the most stress to least before breaking
CVC>composite>amalgam
True or false, the composite interface should be continuous and strong?
True
