During construction of a denture and many other appliances, wax is used as a modeling material. Different types of waxes are used to prepare patterns for alloy castings. There are many varieties of waxes used, both in clinic and laboratory. Each has particular properties depending on what is it used for.
Dental waxes contain natural waxes, synthetic waxes and additives.
Classification of dental waxes
According to origin
- Mineral
- Plant
- Insect
- Animal
According to use
Pattern waxes
- Inlay casting
- RPD casting
- Base plate
Processing waxes
- Boxing
- Utility
- Sticky
- Carding
- Shellac
Impression waxes
- Corrective
- Bite registration
According to ISO Classification
Type 1 (Casting wax)
- Class 1 – Soft
- Class 2 – Hard
Type 2 (Baseplate wax)
- Class 1 – Soft
- Class 2 – Hard
- Class 3 – Extra hard
General properties of wax
Melting range
Waxes have melting range than melting point.
Thermal expansion
Waxes expand when subjected to a rise in temperature and contract as the temperature is decreased.
Mechanical properties
The elastic modulus, proportional limit and compressive strength of waxes are low compared to other dental materials. These properties are strongly dependent on the temperature.
Flow
Important especially in inlay waxes. When melted, the wax should flow readily into all the parts of the die. Flow is dependent on:
- Temperature of the wax
- Force applied
- The length of time the force is applied
Residual stress
The stress may be compressive or tensile in nature.
Ductility
Like flow, the ductility increases increases as the the temperature of the wax is increased. In general, waxes with low melting points have greater ductility than those with high melting points.
Wax distortion is the most serious problem inlay wax. It is due to release of stresses in the pattern caused due to
- Contraction on cooling
- Occluded gas bubbles
- Change of shape of the wax during molding
- From manipulation – carving, pooling, removal etc.
The amount of residual stress is dependent on the method of forming the pattern, its handling and length of time and temperature of storage of the wax pattern.
Article by Dr. Siri P. B.
