Dental Waxes

Question 1

Dental wax used for pattern of metal casting

Answer 1

Inlay/Casting wax

Question 2

Characteristics of wax:

Answer 2

• amorphous (no crystal structure), organic
• solid at room temp
• melts without decomposition (makes it good for casting)

Question 3

Sources of dental wax:

Answer 3

• mineral petroleum distillation (paraffin, microcrystalline, ceresin)
• plants
  (carnauba, candelilla)
• insects
  (beeswax, composition varies)
• synthetic
  (highly refined, differ chemically, similar properties to natural waxes)
• additives
  (stearic acid, oils, resins, rosins, adjust flow and toughness)

Question 4

Composition of dental waxes:

Answer 4

• hydrocarbons or esters
• complex combo of organic compounds with a high molecular weight
• composition of each wax varies

Question 5

Primary component of casting wax:

Answer 5

paraffin (60%)

Question 6

Dental wax jas a melting point

Answer 6

Fasle! It has a melting range. not a melting point

Question 6

Dental wax melting temperature increases with —— molecule weight

Answer 6

increasing

Question 7

Which material has the largest thermal expansion coefficient in all restorative dentistry?

Answer 7

dental wax

Question 7

What is dental wax held together by?

Answer 7

secondary valence forces

Question 8

mineral vs plant waxes…. which have greater force?

Answer 8

plant waxes (esters) stronger than mineral waxes (hydrocarbons)
- still both weak forces

Question 9

What are the 2 contractions?

Answer 9

• solidification shrinkage
• cooling contraction

Question 10

Elastic Modulus (rigidity) and strength of dental waxes are:

Answer 10

• low
• depend on temperature

Question 11

What is wetting?

Answer 11

• ability to flow over a surface
• perfect wetting= 0 degrees contact angle

Question 12

What does die lubricant for wetting?

Answer 12

• it aids in the wetting
  (makes slick surface to allow for nice flow of wax over surface of die)
• also called liquid alginate

Question 13

What is flow of wax?

Answer 13

• degree of plastic/permanent deformation of a material at a given temps

Question 14

What are the 3 things flow depends on?

Answer 14

• temp
• force applied
• time force is applied

Question 15

Which dental wax is harder with lower flow for direct technique in oral cavity?

Answer 15

type I
- not used much anymore

Question 15

When is residual stress present?

Answer 15

ALWAYS present in the pattern
- if molded under compression= it will expand (not good and can raise margin)
- if molded under tension= contraction (not good)

Question 16

Which dental wax is soft for indirect technique on stone model?

Answer 16

type II
- warpage is a problem in both types of waxes

Question 17

Big problems were concerned with in dental wax

Answer 17

• development/release of internal stresses
• non uniform storage temps
• carving that induces stress
• warming pattern