Lecture 2 Flashcards by Savannah Glenn

Looks good
Functions properly
Longevity

Patient satisfaction

-goal of dental material

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Do models have limitations?

Yes

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contact angle
used to measure how liquid
interacts with solid

Measure

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Cannot Know Everything About a Given Material

or System

Models

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Unfilled diluted resins
Self or light cured
Clear or opaque
Radiopaque

Sealants

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Anticipated on the basis
of the Hydrophobicity
(water-hating) and
hydrophilicity (water
loving) of materials

Wetting

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Allow penetration into areas with water

Hydrophilic primers

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Solvent that hydrophllic primers are mixed with

Alcohol or acetone

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Viscosity of hydrophilic primers

Low

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Allows for attatchment to composite

Hydrophilic primers

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Will wet hydrophlic surfaces

Hydrophlic chemicals

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Important anytime two different materials come into contact

Surface wetting

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Important in impression materials, adhesives and bacterial adhesions

Surface wetting

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involve changes in the primary and secondary

bonding of the material

Chemical properties

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generally affected by chemical and

electro chemical reactions

Primary bonding

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generally affected by processes

such as adsorption (onto) and absorption (into)

Secondary bonding

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The spontaneous destructive oxidation of metals

Corrosion

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Do all metals corrode?

Yes

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Copper roofs turn

green

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What color do amalgam filling turn over time?

black

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Designed to minimize corrosion

Gold alloys

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recently deemed a noble metal ADA

Titanium

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Desirable for ceramic to metal bonding

Metal oxides (ceramics)

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Metal corrosion that leads to destruction

Active

Gamma 2

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Metal corrosion that produces corrosion film that prevents further corrosion

Passive | Titanium implants

Metal corrosion of noble metals

Immune | gold

Electrochemical corrosion

Active

Corroding metal

anode

Different metal | -Passive-supplied electrons to solution

Cathode

A conducting environment for ionic movement

electrolyte

An electrical connection | between the anode and cathode for the flow of

Electron current

Two phases in amalgam

Anode and cathode

normally occurs through | dissolution of oxides created by hydrogen bonding effects of water in local areas of high acidity.

Chemical dissolution

How are ceramics affected by dissolution

Chemical dissolution

- Absorption of water into polymers | - Hydrolytic degradation and release of components

How polymers are affected by dissolution

Absorption of water into polymers

Dimensional changes

Hydrolytic degradation and release of components

Contribute to wear problems with composites

Metal ion interation

Hg, Ni

Biological properties are interrelated with

- Degradation properties | - Polymerization process or processing

Biological properties are

dynamic

Describe how a material responds to loads | forces

Mechanical properties

Single dimension of force

- Compression - Tension - Shear

Combinations of forces

- Torsion (twisting) - Flexsion (tensile) - Diametral compression (tensile)

Measures of absorbed energy by material

Resilience and toughness

Before deformation occurs

Resilience

Before failure or fracture occurs

toughness

Time and temperature dependent

Mechanical events

Measures of absorbed energy by material

Hardness

Indent with a load and measure size of indentation

Hardness

Measures a Materials Resistance to Crack Propagation

Fracture toughness

Has High Clinical Correlation to Clinical Wear Data

Composits- fracture toughness

Deformation over time in response to low constant | stress

Creep (strain relaxation)

Deformation over time in response to low constant | strain

Stress relaxation

Multiple cycles of low stress

Fatigue

Effects of forces on the motion of biomaterials and biologic structures

Biomechanics

``` Teeth and restorations (and therefore restorative materials) must withstand forces in service during ```

Mastication and fabrication

Are teeth rigid?

When teeth are subject to chewing forces (stresses) they undergo

Subclinical movements (Strains)

usually associated with | heavy wear facets

Abfractions

Cyclic tension and compression of enamel rods lead to

Microfractures

transfers stress from | enamel to dentin

DEJ

B-L rigidity of teeth

Cuspal independence

How do teeth fail or fracture?

- Single cycle overload | - Fatigue

“unexpectedly bit on cherry pit or bone” (rare)

Single cycle overload

- cyclic loads well below | breaking load

Fatigue

- “I was eating something soft” (more common) -Slow crack propagation over time

Fatigue

- Restorative material - Tooth structure - Interface (stress transferred)

Biomechanical unit