Physical properties of dental materials

Question 1

3 basic physical structures (forms) of dental materials (and all matter)

Answer 1

1. solids: shape and volume
2. liquids: volume and no shape
3. gases: no shape and no volume

Question 2

measuring solids

Answer 2

• density
• hardness
• elasticity
• stiffness
• ductility (tensile strength)
• malleability
• brittleness

Question 3

what is density

Answer 3

• the compactness of a material

Question 4

what is hardness

Answer 4

• used to define a material’s resistance to wear and abrasion

Question 5

what is elasticity

Answer 5

• ability of a material to deform and then return to its original shape

Question 6

what is stiffness

Answer 6

• the resistance to deformation

Question 7

what is ductility

Answer 7

• tensile strength, the ability of a material to be pulled or stretched under tension

Question 8

what is malleability

Answer 8

• the ability to be compressed easily into a thin sheet

Question 9

what is brittleness

Answer 9

• materials with poor ductility

Question 10

in general

Answer 10

• metals = ductile and malleable

- ceramic = brittle

Question 11

what is viscosity in liquids

Answer 11

• the resistance of a liquid to flow (viscous material = decreased flow)

Question 12

what is thixotropic materials (liquid)

Answer 12

• liquids that flow more easily under mechanical forces

Question 13

classifying materials by application as:

Answer 13

• preventive
• therapeutic
• restorative

Question 14

what is direct fabrication

Answer 14

• fabricated directly in the mouth

- ie. amalgam, composite

Question 15

what is indirect fabrication

Answer 15

• fabricated outside of the mouth, then placed into the oral cavity
• ie. crown and bridge, onlays, inlays, dentures

Question 16

composition of materials can be:

Answer 16

• water and powder
• liquid and powder
• paste and paste
• paste and initiator

Question 17

reactions can be:

Answer 17

• physical (evaporation or cooling of liquids)

- chemical (creating new primary bonds

Question 18

what is mixing time

Answer 18

• the amount of time needed to bring the components together to form a homogeneous mix

Question 19

what is working time

Answer 19

• the amount of time permitted to manipulate the material in the oral cavity

Question 20

what is the initial set time

Answer 20

• begins when the material no longer can be manipulated

Question 21

what is the final set time

Answer 21

• when the material has reached its ultimate state

Question 22

3 different types of setting:

Answer 22

1. chemical-set materials: chemical reactions of a catalyst and a base
2. light-activated materials: light initiates the reaction stage
3. dual-set materials: begin with the initiation of a blue light source, then continue the set with a chemical reaction

Question 23

manipulation can be done:

Answer 23

• quickly/slowly
• on a paper pad/glass slab
• handmixing/automix dispenser

Question 24

what is shelf life

Answer 24

• the deterioration and change of quality of the material over time

Question 25

attention to date of expiry

Answer 25

• important for consistency in the optimum characteristics of the product

Question 26

in summary

Answer 26

• physical structure

- important to refer to the manufacturer’s directions for instructions in storage, proportioning, mixing