Dental Materials: Chapter 2

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

material science

subgroup of material science

dental materials

What does restorative materials have to have in order to withstand forces that occur when we bite or grind food?

strong atomic bonds

What are three phases of materials?

solid
liquid
gas

Describe gas and give an example

atomic bonds between gas molecules are very week, no molecular organization, example is condensation of water vapor

Describe liquid and give an example

stronger attraction between molecules but do not strong enough to have shape. Short-range order
example is water

consistent spatial relationships among atoms or molecules 5 to 10 neighbors apart

short-range order

Describe solids and give an example

strongest attraction between atoms and molecules. desk is an example.

___________ solids have a consistent spatial relationship of atoms or molecules repeated hundreds to thousands to millions of times that is called _____ ______ ______

crystalline
long-range order

have the same atomic bonds present in crystalline materials, but have only short-range order, much like liquids

amorphous

atomic bonds are a result of

electromagnetic force

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

primary bonds

electrons in the outer shell of atoms are involved in chemical reactions and atomic bonding called

valence electrons

electrons being given up by one atom and being accepted by another

ionic bond

two atoms are the result of two atoms sharing a pair of electrons

covalent bonds

have characteristic properties that allow us to easily identify a meterial being a metal

metals

similar to covalent bonds in that valence electrons are shared between atoms. Difference is that the electrons in a metal object are not shared by two atoms, instead they are shared by all atoms that make up that object

metallic bonds

result of partial charges from an uneven distribution of electrons around an atom or a molecule

secondary bonds

one atom involved in the bond is partially positive, and the other is partially negative. What occurs?

permanent dipole

this is a special case of permanent dipole; atom containing only one electron

hydrogen bond

Their bonds are the result of an intermittent, uneven distribution of electrons around the atoms or molecules. These weak bonds are called

fluctuating dipole

Ceramic material is bonded with

ionic bonds

composed of long chains of covalently bonded, repeating units

polymers

materials made up of two or more different materials

composites

two-phase materials. They have a mixture of gases, liquids, or solids at microscopic levels

colloids

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

emulsions

The molecules found in a pane of glass can be best described as:
a. crystalline solid, having short-range order only
b. crystalline solid, having both short-range and long-range order
c. amorphous solid, having long-range order
d. amorphous solid, having

d. amorphous solid, having short-range order

a partial charge resulting form an uneven distribution of electrons around an tom forms a bond known as
a. metallic
b. secondary
c. covalent
d. ionic

b. secondary

A notable advantage of using ceramic materials in dentistry is the property of
a. transparency
b. translucency
c. opacity
d. brittleness

b. translucency

A dental polymer with many cross-links as compared to one with no cross-links would be a dental material that is
a. flexible but strong
b. flexible and weak
c. stiff and strong
d. stiff but weak

c. stiff and strong

All of the following are examples of a composite except:
a. set Jell-O with sliced pineapples
b. enamel
c. fiberglass
d. tin foil

d. tin foil

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
a. permanent dipole
b. fluctuating dipole
c. hydrogen bond
d. primary bond

a. permanent dipole

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
a. metal
b. ceramic
c. polymer

a. metal

A mixture of two liquids that do not blend together to form one liquid is termed
a. composite
b. emulsion
c. colloid
d. solution

b. emulsion

When two atoms share a pair of electrons, the resulting atomic bond is termed _______ bond
a. secondary
b. ionic
c. covalent
d. metallic

c. covalent