bds2 intro to dental materials

Question 1

questions to ask regarding treatment plan for removal of caries and restoration

Answer 1

which material is suitable
how to use material
explain the options to the patient
select the material

Question 2

the behaviour of dental materials affects which stages of the clinical episode, explain why

Answer 2

selection - best type
preparation - cavity design and tooth surface
placement - technique
performance - quality of fit and longevity
patient expectations - aesthetics and durability

Question 3

what does the CE mark indicate

Answer 3

that a material is safe provided you use it for the designated purpose

Question 4

list some common restorative materials

Answer 4

amalgam
composites
glass ionomer cements
composers
porcelain

Question 5

which impression material is a hydrocolloid

Answer 5

alginate

Question 6

which impression material is an elastomer

Answer 6

polysulphides
polyethers
silicones

Question 7

features of composite resin in restorations

Answer 7

initially will flow out of the cartridge (low and high viscosities exist)
sets within margins and hardens

Question 8

what is the negative replica of impressions materials

Answer 8

the recorded dentition - ie initial impression

Question 9

describe the features of impression materials

Answer 9

flows into tray with low viscosity and undergoes a setting reaction to become firm and stable

Question 10

what is the positive replica of an impression

Answer 10

gypsum - the “fake” teeth

Question 11

what can happen to a material when forces are applied

Answer 11

stretch or compression depending on the force
deformation either temporary or permanent
fracture

Question 12

calculation for stress

Answer 12

force / unit area

Question 13

what are the units for stress

Answer 13

pascals

Question 14

what is strain

Answer 14

change in length / original length

Question 15

what is Youngs modules discussing

Answer 15

elasticity

Question 16

what is the definition of Youngs modulus

Answer 16

elastic (Youngs) modulus is equal to stress over strain

Question 17

FS

Answer 17

fracture stress

Question 18

PL

Answer 18

proportional limit

Question 19

mechanical property terms

Answer 19

hard vs soft
strong vs weak
rigid vs flexible
brittle vs ductile

Question 20

what is the typical biting force

Answer 20

500 to 700N

Question 21

biting force in kg

Answer 21

50-70kg

Question 22

what kind of force is biting

Answer 22

compressive

Question 23

force directions for compression

Answer 23

force going up and force going down

Question 24

force directions for tensile

Answer 24

stretching to create fracture - pulling in opposite directions

Question 25

force directions for sheer

Answer 25

one force acting sideways

Question 26

what does tensile force do to dimension

Answer 26

change

Question 27

what is stress measured in

Answer 27

mega pascals

Question 28

describe what happens with forces to the tooth during grinding and chewing

Answer 28

tooth slides along the surface of the other, frictional forces are experienced the tooth surface may be abraded, loss of layers of enamel

Question 29

why is it important that materials adhere to enamel

Answer 29

otherwise the enamel would be removed by masticatory forces

Question 30

what to consider when choosing restorative materials

Answer 30

what treatment options are there what material suits each procedure will that material suit the patients needs and requirements

Question 31

what's the design of amalgam

Answer 31

undercut

Question 32

what is the design of composite resin

Answer 32

minimal

Question 33

what is the retention type of amalgam

Answer 33

mechanical

Question 34

what is the retention type of composite resin

Answer 34

adhesive

Question 35

what are the benefits of an undercut design

Answer 35

keeps the material in place

Question 36

what are the key features required for materials when filling the cavity

Answer 36

the material must be pliable, fit the shape of interest, and set to form hard, strong material

Question 37

what is the failure mechanism of a fracture

Answer 37

large force causes catastrophic destruction of materials structure

Question 38

what is the failure mechanism of hardness

Answer 38

ability of surface to resist indentation

Question 39

what is the failure mechanism of abrasion

Answer 39

material surface removal due to grinding

Question 40

what is the failure mechanism of abrasion resistance

Answer 40

ability to withstand surface layers being removed, so compromising surface integrity

Question 41

what is the failure mechanism of fatigue

Answer 41

repetitive small stresses cause material fracture

Question 42

what is the failure mechanism of creep

Answer 42

gradual dimensional change due to repetitive small forces

Question 43

what is the failure mechanism of deformation

Answer 43

applied stress causes permanent changes in materials dimensions but does not fracture it

Question 44

what is the failure mechanism of debonding

Answer 44

applied forces sufficient to break the material to tooth bond

Question 45

what is the failure mechanism of impact

Answer 45

large, sudden force causes fracture

Question 46

what is abrasion

Answer 46

when the tooth grinds along the opposing tooth surface or restorative material at its surface. the surface is abraded and there is loss of material surface layers, causing a roughened surface

Question 47

how are most failures brought about

Answer 47

when repeated loads are applied, small flaws in a material grow and this allows the fracture when only a relatively small force is applied

Question 48

what is creep

Answer 48

repetitive forces causing dimensional change

Question 49

what results in permanent deformation

Answer 49

releasing stress that is greater than the elastic limit

Question 50

how is debonding used in orthodontics

Answer 50

to remove the appliance, shear force is applied to separate the bracket/bonding material from the tooth surface

Question 51

main chemical properties for dental materials

Answer 51

setting mechanism setting time corrosive potential

Question 52

main physical properties for dental materials

Answer 52

viscosity thermal conductivity thermal expansion density radiodensity

Question 53

elements of the oral environment that can impact dental material behaviours

Answer 53

saliva temperature variations pH variations oral bacteria