Waxes

Question 1

What does thermoplastic mean?

Answer 1

• solid at room temperature
• at higher temperatures melt with no decomposition

Question 2

What are waxes formed around?

Answer 2

cristalline structure

Question 3

What is the ‘softening temperature’ of waxes?

Answer 3

the temperature before they melt when they become pliable

Question 4

What happens when waxes are at softening temperature?

Answer 4

undergo solid-solid transition
- results in profound change in physical properties, becoming pliable and mouldable
- offers scope for manipulation

Question 5

What are the components of waxes?

Answer 5

• animal
• vegetable - from tress and plants
• mineral - hydrocarbons

Question 6

What is an example of an animal component of wax?

Answer 6

beeswax - partially crystalline natural polyester

Question 7

What is an example of a vegetable component of wax?

Answer 7

carnauba wax, candelilla wax

Question 8

What is an example of a mineral component of wax?

Answer 8

paraffin wax (straight chain), microcrystalline (branched chain)

Question 9

What are the dental applications of waxes?

Answer 9

• modelling
  
  • indirect - modelling wax
  • direct - inlay wax
• carding
• boxing in
• joining components to facilitate union

Question 10

By international convention, how thick is a base plate sheet of wax?

Answer 10

1.5mm thick

Question 11

What type of wax is used to set denture teeth in?

Answer 11

modelling wax

Question 12

What colour is inlay wax?

Answer 12

blue

Question 13

What is inlay wax used for?

Answer 13

to wax up a crown etc

Question 14

What can be used to repair dentures?

Answer 14

sticky wax

Question 15

What is carding wax used for?

Answer 15

for putting denture teeth on e.g. when you have a stip of denture teeth on the ‘senator’ strip that is carding wax they are placed on

Question 16

Other than the waxes, what are the other variety of components incorporated in?

Answer 16

• waxes
• resins
• oils
• fats
• pigments

Question 17

What dictates the properties of wax products?

Answer 17

the blending off the different components

Question 18

Between what temperatures do paraffin waxes soften?

Answer 18

~37-55 degrees C

Question 19

Between what temperatures so paraffin waxes melt?

Answer 19

~48-70 degrees C

Question 20

What can be added to paraffin wax to adjust the properties?

Answer 20

microcrystalline (MP 65-90 degrees C)

beeswax

carnauba/candelilla

Question 21

What effect does adding microcrystalline to paraffin wax have?

Answer 21

increases melting point, decreases softening point

Question 22

What effect does adding beeswax to paraffin wax have?

Answer 22

decreases brittleness, decreases flow

Question 23

What effect does adding carnauba wax to paraffin wax have?

Answer 23

enbrittles the wax

Question 24

What are the steps of wax being used a a modelling material (lost wax technique)?

Answer 24

• used to form dental restoration or prosthesis
• embedded in investment material
• boiled/burnt out
• vacant space for definitive restoration/prosthesis material

Question 25

Why is modelling wax used when making acrylic dentures?

Answer 25

• withstands intraoral temperature
• amenable to chairside/laboratory adjustment
  
  • tough enough for undercut withdrawal
  • no tearing/chipping/flaking
• no residue in investment mould upon boiling out

Question 26

What wax is used when making crowns/inlays/bridges?

Answer 26

inlay wax (blue)

Question 27

What is a unique feature of inlay wax?

Answer 27

locks into undercut and will fracture if you try to remove it
- will tell you whether your cavity has undercuts

Question 28

What are the features of inlay wax?

Answer 28

• fractures if locks into undercut
• good colour contrast
• no tearing/chipping/flaking
• no residue in investment mould upon burning off

Question 29

What is an example of a wax specialist component?

Answer 29

wax patterns preformed for components of partial denture and bridgework