Are thermoplastic materials which are normally solids at room temperature but melt, without decomposition, to form mobile liquids. Dental waxes are used in a wide variety of clinical and laboratory dental procedures.
They are composed of a mixture of thermoplastic components from natural & synthetic sources.
Natural waxes are produced from:
Plants________ carnauba wax
Minerals_______ paraffin wax
They are combined or mixed with synthetic waxes, gums, fats, oils, resins & coloring agents.
1- Melting range
3- Excess residue
4- Dimensional change
A range of temperatures at which each component of the wax will start to soften & then flow.
Controlling the temperature of the wax allows operator control of the viscosity of the wax.
A flame source is needed if a flowable state is desired.
It is the movement of the wax as it approaches the melting range.
Temperature ____ viscosity ____ liquid
Control of the flow & melting range is important in manipulating the wax.
In the clinic:
If we are doing a wax bite registration, a melting range that is only slightly higher than mouth temp is desirable.
And it is important that the wax does not require temp much greater than mouth temp to soften (uncomfortable to the patient).
In the Lab:
Waxes may have a much higher melting range.
However, even for lab purposes this may be undesirable.
e.g. in the boxing of an impression using wax, it is more desirable to mold the wax using the heat of the hand or warm water rather than having to use a flame.
A wax film remaining on an object after the wax is removed.
If excess residue remains after the wax is removed, it may result in inaccuracies in the object being produced.
Important in the lost wax technique when the wax pattern is melted out of the investment mold.
Waxes expand when heated & contract when cooled, the thermal expansion & contraction of waxes is greater than any other dental material.
Important for pattern waxes.
Pattern waxes: a duplicate of the restoration carved in the wax.
If a wax is heated too far above the melting range or heated unevenly, expansion above acceptable standards will result in inaccuracies in the final casting.
If waxes are allowed to stand, dimensional changes occur from the release of residual stress. (It should be invested and casted within 30 min after carving the wax).
Classification of dental waxes:
a) Pattern wax
b) Processing wax
c) Impression wax
Several forms are available as sticks, sheets, blocks, & tins.
Waxes have unique coloring to distinguish them in use.
Are used in the construction of metal castings & bases for dentures through lost wax technique.
a- Inlay waxes
Used to produce patterns for metal casting using the lost wax tech.
e.g. inlays, onlays, crowns & pontics.
These waxes are supplied in:
Several forms: sticks, pellets & tins.
Dark colors: blue or green.
They are labeled: hard, medium & soft (according to their melting ranges).
They are not sticky to touch.
Important properties for pattern waxes:
• Low thermal expansion
• Complete removal of excess residue
• Appropriate melting ranges.
There are two types:
Type I wax: used directly in the mouth softened & placed into the prepared tooth in the direct waxing technique.
Has a lower melting range for the comfort of the patient & the accuracy of the wax on removal.
Has a softening point slightly higher than the mouth temp.
All the limitations of the mouth must be considered.
Type II wax: more frequently used, where wax is melted onto a die outside the mouth in the indirect technique.
Most dentists prefer to use this & have a dental laboratory technician produce the wax pattern and casting.
b- Casting waxes
Used to construct the metal framework of partial and complete dentures.
These come in sheets & preformed shapes.
The physical properties are similar to inlay wax except the melting range.
The melting range is only important for laboratory procedures, because these waxes are not softened in mouth.
c- Baseplate wax
They are sheets of wax generally pink in color to simulate the color of the gingiva.
• These sheets are layered to produce the form on which denture teeth are set. (occlusal or bite rims) This initial form is then tried into the mouth to establish denture dimensions.
• Spacer in custom trays.
• Pattern for plastic portion of dentures.
The wax must not distort at mouth temperatures.
Used primarily to aid in dental procedures both clinically & in laboratory.
a- Boxing wax
It is used to form the base portion of a gypsum model.
The 1.5-inch-wide, red strip of boxing wax is wrapped around the impression to produce a form into which the
gypsum is poured.
It is easily manipulated and slightly tacky at room
temperature, allowing it to adhered to itself to secure the boxed
b- Utility wax
Also called periphery wax.
It comes in ropes and sheets that are easily manipulated at room temp.
These come in various colours of pink, white & red.
Uses of wax ropes:
• To adapt the periphery of the impression tray to customize the tray & aid in patient comfort.
• Provide a better fit into the vestibule & control of the movement of the impression material.
• To cover sharp brackets and wires in orthodontic patients.
Use of wax sheets:
May be layered to form a horseshoe shape & used for wax bite registrations.
c- Sticky wax
Used to adhere components of metal, gypsum, or resin together temporarily during fabrication & repair.
It comes in orange sticks that at room temp are hard & brittle, but when heated under flame become soft & sticky.
Because it is brittle, even the slightest torque will fracture the wax. (Important alert for the operator).
d- Alu wax
It is used to get occlusal registration.
Contains aluminium particles and it is brittle.
It is available in thin & thick sheets.
It is used to obtain impressions of the oral structures.
a- Corrective impression wax
It is used in conjunction with other impression materials in the process of taking edentulous impressions.
This wax flows at mouth temp & is used within another (original) impression material to correct undercut areas.
They exhibit high flow & distort on withdrawal from undercuts. (disadv)
They are replaced by elastomeric impression materials.
b- Bite registration wax
1- Bite wafers:
It is used to produce wax bite registrations for articulation of models.
The preformed horseshoe shapes are often reinforced with metal particles to provide stability.
It is susceptible to distortion at temp slightly higher than mouth temp.
2- Occlusal indicator wax:
It is used to detect areas of premature occlusal contact.
Supplied in scored strips & is dark green, yellow or blue in colour.
• Wax should be softened evenly in dry heat, with warm hands, or by flame.
• If a wax is softened by flame it should be rotated above the flame until it evenly softens or flows.
• Melted wax should be added in layers onto an object.
• Wax patterns should be invested within 30 min of carving, because of changes by relaxation of residual stress.
• Waxes such as boxing and utility wax are slightly tacky at room temp to help them adhere to themselves, But they must remain dry.
• To avoid distortion of waxes, they should be stored at or slightly below room temp.