dental materials ch 2-3 quiz

conditions of oral enviornment

• always wet

• temperature changes (ice cream to coffee)

• pH changes (acidic to alkaline)

materials used in dentistry must withstand

• rapid changes in force, temperature, and chemistry

• they have both engineering and biocompatibility

biting forces can exceed

• 28,000 PSI

hue

• main color

• the color of a tooth or restoration (may include a mixture of colors)

chroma

• intensity (gray, yellow, white)

• the intensity or strength of a color

value

• how light or dark the color is

• a low .. indicates a darker color and a high .. indicates a brighter color

metamerism

• color due to lighting

transparent

• optical property in which light passes directly through an object

translucency

• optical property in which varying degrees of light pass through or are absorbed by an object

opaque

• optical property in which light is completely absorbed by an object

the oldest of the major classes of materials

• metals

metal

• defined by a set of characteristics including high thermal and electrical conductivity, ductility, opacity, and luster

galvanism

• electric current being transmitted between two dissimilar metals

• can cause a shock

shearing force

• two surfaces slide against each other

tensile force

• opposite directions to stretch an object

compressive force

• compress an object

torsion/ torque

• twisting force that combines tensile and compressive

coefficient of thermal expansion

• is the measurement of change in volume or length in relationship to change in temperature

thermal conductivity

• is the rate at which heat flows through a material

dimensional change

• is a change in the size of matter

• for dental materials, this usually manifests as expansion caused by heating and contraction caused by cooling

microleakage

• leakage of fluid and bacteria caused by microscopic gaps that occur at the interface of the tooth and restoration margins

stress

• type of force applied to a material or surface

strain

• force is applied to a material or surface

over time stress and strain can cause

• fatigue failure

fatigue failure

• a fracture resulting from repeated stresses that produce microscopic flaws that grow

physical properties of materials

• can be observed

  • color

  • mass

  • density

  • boiling point

  • melting point

  • molecular weight

mechanical properties

• can be measured

  • thermal conductivity

  • coefficient of thermal expansion

  • hardness

  • toughness

  • strength solubility

  • elasticity

primary bond

• strong

  • include ionic, covalent, metallic

  • ex: an adhesive

secondary bond

• weaker and breaks easily

• what we primarily use in dentistry

  • hydrogen bond, permanent and temporal dipoles

  • ex: sealant

viscosity

• thickness of a material

thixotropic

• flows under pressure

• mixing, shaking, stirring

toughness

• the ability of a material to resist fracture

resilience

• the ability of a material to absorb energy without permanent deformation

density

• the measure of the c weight of a material compared with its volume

hardness

• the resistance of a solid to penetration

elasticity

the ability of a material to recover its shape completely after deformation from an applied force

allloys

• strength

• ability to conduct electricity and heat

• malleability

• ductility

• luster

  • ex: amalgam restorations, implants, partial denture frameworks, crowns, bridge

ceramics

• rigid and brittle

• melt at high temperatures

  • ex: esthetic crowns and veneers

polymers

• occur in long chains that give certain properties depending on how the chains are linked

  • ex: denture bases and teeth

characteristics of and IDEAL dental material

• biocompatible (non-toxic, non-allergenic, non-irritating)

• mechanically stable and durable against stress and strain in oral cavity

• dimensionally stable

• minimal thermal conductivity

• esthetic

• easy to manipulate

• strong adhesion and bonding

• tasteless/odorless/hydrophilic

• cost effective

an ideal restorative material should

• be biocompatible to existing tooth structure

• should bond permanently to tooth structure or bone

• should match the natural appearance of tooth structure and other visible tissues

• exhibit properties similar to those of tooth tissues (enamel and dentin)

• be capable of initiating tissue repair or regeneration of missing or damaged tissues

a defining characteristic of a solid is that it has

• shape and volume

the type of primary bond where atoms share electrons in their outer shells

• covalent bond

the correct term for describing the maximal amount of stress a material can withstand without breaking is

• ultimate strength

when the weight of a material increases in relationship to its volume, this is described as

• dense

hardness determines the materials ability to

• resist scratching

when deformation is not permanent and a material recovers, it has good

• elasticity

resistance to flow is known as

• viscosity

thixotropic materials are those that

• flow under mechanical force

mixing time is the length of time from

• the beginning of mixing to the beginning of working time

a material mixed slowly on a cooled glass surface will

• have a shorter working and longer setting time

the safe interaction of a dental material with the rest of the body is defined as the materials

• biocompatibility

the study of dental materials includes knowledge of

• the chemical reactions of the material

• the physical reactions of the material

• the ways to manipulate the material

  • (all of the above)

the internal reaction to an externally applied force is

• stress

when increasingly higher forces are applied to a material it will eventually fracture and the point of fracture is called

• ultimate strength

material subject to repeated stresses such as in mastication may be subject to fracture due to

• fatigue failure

which of the following restorative materials is the most soluble?

• glass ionomer

corrosion is of greatest concern for which of the following restorative materials?

• amalgams

surface discoloration of a metal restoration is called

• tarnish

restorative materials with values of thermal conductivity similar to enamel include

• composite resin

susan has just had an MOD amalgam placed on tooth #30. when biting, this tooth is in contact with a gold crown on tooth #3. Susan complains of electric shock sensation and metal taste. this is likely due to

• galvanism

microleakage may be responsible for

• recurrent decay

• marginal staining

• postoperative sensitivity

  • (all of the above)

excessive film thickness of cements may cause

• improper seating of the restoration

the leakage of fluids and debris extending along the tooth restoration interface is called

• microleakage

colonies of bacteria growing on the teeth are called

• dental plaque

color shades can vary depending on the incident light or source of light. this is called

• metamerism

the term that describes the intensity of color

• chroma

oral biofilm is

• a complex organization of microorganisms on oral surfaces and restorations