Dental Materials 2 D

Front 1

Understanding the behavior of materials is important in the ----, ---- and ---- of dental materials. The behavior of any given material is based on the ---- in that material.

Back 1

selection, placement, maintenance, atomic bonds

Front 2

the part of the physical sciences that seeks to explain the properties and performance of materials by examining their internal structure.

Back 2

Materials science

Front 3

---- and restorative materials need to be stronger—and to have stronger ---- —than the food we eat.

Back 3

Teeth, atomic bonds

Front 4

the three phases of materials

Back 4

solid, liquid, gas

Front 5

The atomic bonds between gas molecules are very ---. These bonds are easily broken by the normal microscopic vibrations of atoms at ----. These atomic vibrations are the result of the ---- of the material. Gases have no molecular organization and will take on the ---- of the container that they fill. If thermal energy is removed by cooling, gases condense into ----.

Back 5

weak, room temperature, thermal energy, three-dimensional shape, liquids

Front 6

Liquids have --- attraction between mol-ecules than gases do, but this attraction is not strong enough to carry a --- or to maintain a --- without support. The attraction between molecules results in --- order. Molecular attraction keeps liquids from ---, but not always from ---. Other characteristics of a liquid are vapor pressure, boiling temperature, ---, and ----.

Back 6

stronger, load, shape, short-range, boiling, evaporating, viscosity, surface tension

Front 7

a consistent spatial relationship among atoms or molecules 5 to 10 neighbors apart.

Back 7

Short-range order

Front 8

Solids exhibit the --- attraction between atoms and molecules. The atomic bonds of solids maintain the --- of objects and --- external forces placed on them. Solids can be classied as -- or ------ Table salt, diamonds, and the hydroxyapatite of teeth are crystalline solids. Crystalline solids have both --- and --- order of their atoms or molecules.

Back 8

strongest, shape, resist, crystalline, amorphous, short-range, long-range

Front 9

have a consistent spatial relationship of atoms or molecules repeated hundreds to thousands to millions of times that is called long-range order

Back 9

Crystalline solids

Front 10

have the same strong atomic bonds present in crystalline mate-rials, but have only short-range order, much like liquids.

Back 10

Amorphous solids

Front 11

The long-range order of an amorphous solid is more ---- or ---. Some solid objects are stronger than others. The difference is determined by the --- of atoms that make up the material and the ---- of the atomic bonds that hold the material together.

Back 11

irregular, disorganized, type, strength

Front 12

Atomic bonds are a result of ----. The electronic force causes --- charges to attract --- charges and --- charges to attract --- charges. Positive charges are --- by positive charges, and negative charges are --- by negative charges.

Back 12

electromagnetic (EM) force, positive, negative, negative, positive, repelled, repelled

Front 13

the strong bonds between atoms that involve the transfer or sharing of electrons between atoms.

Back 13

Primary bonds

Front 14

The atom is made of ---, ---, and ----. The protons and the neutrons make up the ----; the electrons move around the nucleus in ----.

Back 14

protons, neutrons, and electrons, nucleus, shells

Front 15

Electrons in the outer shell of atoms that are involved in chemical reactions and atomic bonding.

Back 15

valence electrons

Front 16

the result of an electron being given up by one atom and being accepted by another.

Back 16

Ionic bonds

Front 17

the result of two atoms sharing a pair of electrons

Back 17

Covalent bonds

Front 18

valence electrons are shared between atoms.

Back 18

Metallic bonds

Front 19

Metals are typically ---, ---- materials. They are good conductors of both --- and ----, are cold to the touch at ----, and, if shaped properly, will ring like a --- if struck.

Back 19

dense, heavy, electricity and heat, room temperature, bell

Front 20

The electrons in a metal object are not shared by --- atoms; instead, they are shared by --- the atoms that make up that object

Back 20

two, all

Front 21

the result of partial charges from an uneven distribu-tion of electrons around an atom or a molecule.

Back 21

Secondary bonds, or van der Waals forces,

Front 22

A permanent partial charge,

result in weak bonds,

Back 22

permanent dipole

Front 23

The hydrogen atom contains only --- electron. When this single electron is pulled away from the hydrogen nucleus by a “greedy” atom, such as oxygen, the nucleus is left partially unshielded, but to a much greater extent than in other elements with multiple electrons. The resulting interaction between molecules results in a bond that is much --- than other secondary bonds.

Back 23

one, stronger

Front 24

he result of an intermittent, uneven distribution of electrons around the atoms or molecules.

Back 24

fluctuating dipole

Front 25

The atoms that make up a material and how these atoms are bonded determine the --- of that material. Materials can be classied into three categories based on their primary atomic bonds: ----, ---- and -----. A fourth category is ----.

Back 25

properties, metals, ceramics, polymers, composites

Front 26

“mixtures” of two materials from two different categories.

materials that are made of two or more different materials.

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composites

Front 27

Metals are held together with ----. Few metals, however, have pure metallic bonds. Most metals have bonds that are predominantly metallic but that also show some --- or --- tendency. The broad range of mixtures of metallic and other primary bonds results in metallic materials with a ---- of properties.

Back 27

metallic bonds, covalent, ionic, range

Front 28

Gold is ----, meaning that it can easily be bent without breaking yet retains its strength.

Back 28

ductile,

Front 29

The atoms of a ceramic material are bonded with --- bonds. The ionic bond dominates the behavior of the material, resulting in ----, ---- materials. The strong nature of the bonds of these materials is reflected in the ----- needed to process many ceramic materials and their chemical ----.

Back 29

ionic, strong, brittle, high temperature, stability.

Front 30

In dentistry, the notable advantage of ceramic materials is the range of --- that can be produced. Crowns made of ceramic materials are colored to match the appearance of the patient’s natural teeth. These materials are also ---, meaning that some light passes through, as in natural teeth. This translucency gives the ceramic crown a more --- appearance that other materials cannot provide.

Back 30

colors, translucent, natural

Front 31

Ceramic materials are strong when ----, because the atoms are forced together. However, ceramic materials are ---- and --- when pulled or bent.

Back 31

compressed, weak, brittle

Front 32

composed of long chains of covalently bonded, repeating units.

Back 32

Polymers

Front 33

A wide variety of polymers are used in everyday life. Some are soft, weak, and flexible; these are called ----. Others are hard, stiff, and fairly strong; these are called --- or ----. Another important group can be stretched out a great deal and still return to their original shape; these are called --- materials.

Back 33

“plastics”, glassy polymers or resins, rubber

Front 34

Why do polymers exhibit such a wide range of properties?

Back 34

it is the variety of bonds between polymer chains that results in such a wide variety of polymeric materials.

Front 35

The weakest bond between chains is the ---. It's bonds are easily ----, and the chains readily -- by one another at room temperature.

Back 35

flactuating dipole, broken, slide

Front 36

Common composites are mixtures of a --- and a ---, such as fiberglass. Each material that makes up a composite is called a ---. Materials or phases are chosen and combined so that the resulting composite has properties --- than those of either individual material.

Back 36

polymer, ceramic, phase, better

Front 37

mixtures of gases, liquids, or solids at the micro-scopic level.

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Colloids

Front 38

Colloids are also --- materials. Colloids are not true ---- of one material dissolved in another, such as saltwater. Colloids are --- of one material in another, such as fog (a suspension of water droplets in air).

Back 38

two-phase, solutions, suspensions

Front 39

a type of colloid composed of two liquids that do not blend together to form one liquid

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Emulsions

Front 40

One of the main functions of teeth is to start the --- of food. Teeth ---, --- and --- a variety of materials to allow the digestive fluids to access the greater surface area that is inherent in smaller pieces of food. Teeth are --- than the food we eat. The dental restorative materials that are used to replace tooth structure must have these same characteristics.

Back 40

digestion, chop, tear, grind, stronger

Front 41

The molecules found in a pane of glass can be best described as ---

Back 41

Amorphous solid, having short-range order

Front 42

A partial charge resulting from an uneven distribution of electrons around an atom forms a bond known as ----

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Secondary

Front 43

What type of bond is formed when the electrons are shared by all the atoms that make up that object and may be thought of as “positive cores” in a “cloud of negative mobile valence electrons”?

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Metallic

Front 44

A notable advantage of using ceramic materials in dentistry is the property of ----

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Translucency

Front 45

A dental polymer with many cross-links as compared to one with no cross-links would be a dental material that is ----

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Stiff and strong

Front 46

What are examples of a composite?

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Jell-O with sliced peaches, Enamel, Fiberglass

Front 47

When the shared electrons of a covalent bond are not shared equally, and one of the bonded atoms is partially positive and the other is partially negative, a ---- is formed.

Back 47

Permanent dipole

Front 48

The sliding of atoms past each other allows this material to bend, not fracture, and maintain its strength. This material is an example of a ----

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Metal

Front 49

A mixture of two liquids that do not blend together to form one liquid is termed an ----

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Emulsion

Front 50

When two atoms share a pair of electrons, the resulting atomic bond is termed a ----- bond.

Back 50

Covalent