1. Dental Waxes

General definition of dental waxes

Thermoplastic (deform with heat and are solid at room temp) materials with a hydrocarbon structure (hydrophobic)

What are dental waxes derived from?

Are they refined or chemically pure?

They are derived from animal, mineral and plant sources

They are not very refined and thus are not chemically pure

What base waxes are used for all dental waxes?

Almost all Paraffin (base) and some Ceresin (modifier) and are both derived from a mineral source

Paraffin

• Originates as a byproduct of oil fractionation

• Not very Refined

• Inexpensive

Aside from Ceresin, what other modifier waxes are added to the Paraffin base wax?

Carnauba is added to increase melting temperature and to increase hardness and toughness

What is the most undesirable property for ALL dental waxes?

What is the undesirable range in ppm/C

• High Coefficient of Thermal Expansion (CTE) because that means it is affected by small temperature changes such as body heat that can result in deformation (NOT THE SAME THING AS MELTING)

• 200-600 ppm/C

Explain Pyrolysis and what it is important for

What does the wax break down into during Pyrolysis?

• Pyrolysis is the melting of the wax at very high temperatures during casting process to ensure complete breakdown without leaving any residue in investment mold

• Wax breaks up into water vapor and carbon dioxide

______ molecular weight (or average) results in higher _____ and ________ temperatures, but ____ generally does not affect ____

Higher molecular weight (or average) results in higher density and melting temperatures, but MW generally does not affect CTE

Why are colorants added to wax?

Bright colors are used so that margins can be clearly seen when adjusting wax