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Dental Waxes
1.
2. DENTAL WAXES
IT IS RECOMMENDED TO FOLLOW McCABE APPLIED DENTAL MATERIALS
ALONG WITH THIS LECTURE PERSENTATION
REFERENCES FOR THIS LECTURE:
RESTORATIVE DENTAL MATERIALS, CRAIG
NOTES ON DENTAL MATERIALS, COMBE’S
DENTAL MATERIALS, PHILLIPS
3. DEFINITION
Waxes are thermoplastic materials
which are solids at room
temperature but melt without
decomposition to form mobile
liquids*
*Applied Dental Materials, McCabe
4. CLASSIFICATION OF DENTAL WAXES
According to use/application:
Restorative Dental Materials, Craig
6. Type Example Source Structure Properties
a. Mineral Paraffin wax Distillation of crude
petroleum
Straight chain
hydrocarbon,
Polycrystalline
Brittle at ambient
temperature
Microcrystalline / ceresin Distillation of crude
petroleum
Branched chain
hydrocarbon,
polycrystalline
Less brittle than
paraffin due to their oil
content
b. Insect Bees wax Honeycombs Less crystalline than
paraffin wax, more
amorphous
When with paraffin
wax:
-at room temp. makes
it less brittle
-at high temp (e.g.
mouth temp) reduces
the flow of wax
c. Vegetable Carnuaba wax South America palm
tree
- Hard, lustrous, tough
wax.
Blended with paraffin
to harden it and raise
it’s solid -solid
transition temperature
Candella wax Plants - Same as above
Resins and gums Trees - Used to add adhesive
qualities to wax
7. PROPERTIES OF DENTAL WAXES
THERMAL PROPERTIES:
1. Solid-Solid transition temperature: (Tg)
Temperature at which a sharp increase in coefficient of thermal expansion occurs
indicating increased molecular mobility.*
Also called softening temperature or glass transition temperature.
In waxes, at this temperature, transition from a stable crystal lattice
(orthorhombic) to hexagonal form occurs which is present below the melting
point of wax and thus it allows the wax to be manipulated easily without
flaking or tearing. Wax is soft (not melted) at this temperature..
* Dental materials, Phillips
8. 2. Coefficient of thermal expansion: HIGHER COTE than any other dental
material..
Value: 350x10-6/˚C
This will cause the wax to expand n heating and appreciably shrink on
cooling from solidification temp to room temp.
On heating, may expand 0.7% when temp is increased 20 ˚C
On cooling from 37˚C to 25 ˚C , a linear shrinkage of 0.35% occurs
May cause distortion of wax patterns
9. 3. Melting range:
Because waxes may contain several types of molecules, each having a
range of molecular weights, they have melting ranges rather than melting
points
Paraffin: 40-70 ˚C
Microcrystalline: 60-90 ˚C
Bees wax: 65-70 ˚C
4. Thermal conductivity: Low thermal conductivity
10. MECHANICAL PROPERTIES
Low compressive strength
Low modulus of elasticity
RHEOLOGICAL PROPERTIES
1. Flow: The property of flow results from the slippage of molecules
over each other. Waxes show deformation when subjected to constant
load for a period of time. Amount of flow depends upon:
1. temperature of the wax
2. the force bringing about the deformation, and
3. the time the force is applied
Waxes will have a low flow below Tg temp. Flow greatly increases as the melting
point of the wax is approached
11. It is important for inlay wax that is to be used in a DIRECT technique to have:
1. A large flow about 5˚C above mouth temperature so that good details of
cavity can be attained
2. A negligible flow at 37 ˚C so that no distortion occurs upon removal of wax
pattern from oral cavity
INTERNAL STRESSES
Waxes have low thermal conductivity making it difficult to achieve uniform
heating. If a wax is adapted to shape without adequate heating to above Tg
temperature, considerable stresses will develop in the wax. If then the wax is
warmed, relief of stresses will occur resulting in distortion or WARPAGE of wax
pattern. Also warpage occurs b/c waxes have high C.O.T.E
12. MODELLING WAX
A type of pattern wax
Pink Color
Available in sheet form
USES: Making wax pattern of complete and partial dentures
Making wax pattern of orthodontic appliances
Making occlusal rims for recording maxilla-mandibular (jaw) relation
COMPOSITION:
Paraffin wax: 70-80%
Bees wax: 12%
Carnuaba wax: 2.5%
Resins: 3%
Synthetic waxes: 2.5%
METLING RANGE: 44 ˚C-62 ˚C
13. TYPES
For more images, click:
http://ourdentalmaterials.webs.com/apps/photos/album?albumid=15488889
14. INLAY WAX
Type of pattern wax
Various colors (Blue, green, purple)
Available in sticks, cakes, blocks
USES: Preparation of wax pattern for cast metal restorations like inlays, onlays, crowns, bridges
COMPOSITION:
Paraffin wax: 60%
Carnuaba wax: 20%
Ceresin wax: 10%
Bees wax: 5%
Gum Dammar: 5%
TYPES: Type I (soft) For indirect technique
Type II (Hard) For direct technique
For more images, click:
http://ourdentalmaterials.webs.com/apps/photos/album?albumid=15488889
15. CASTING WAX
The pattern for the metallic framework of removable partial dentures and other
similar structures is fabricated from casting waxes.
These waxes are available in the form of sheets, usually of 28- and 30-gauge
(0.40 and 0.32 mm) thickness, ready-made shapes, and in bulk
For more images, click:
http://ourdentalmaterials.webs.com/apps/photos/album?albumid=15488889
16. BOXING WAX
A type of processing wax
Available in thin sheet and sticks
Mouldable at room temp
To form a plaster or stone cast from an impression of the edentulous arch, first a
wax box must be formed around the impression, into which the freshly mixed
plaster or stone is poured and vibrated.
This boxing procedure is also necessary for some other types of impressions.
The boxing operation usually consists of first adapting a long, narrow stick or
strip of wax around the impression below its peripheral height, followed by a
wide strip of wax, producing a form around the entire impression,
17. Sticky wax
A type of processing wax
Adhesive and brittle at room temp
Bright yellow/orange sticks
USES:
used to assemble metallic or resin pieces in a fixed temporary position during soldering or repair
procedures
MELTING RANGE: 60-65˚C
COMPOSITION
Yellow bees wax: 60%
Resin: 17%
Gum dammar: 17%
This wax doesnot flow at room temperature
18. Utility wax
USES:
a standard perforated tray for use with hydrocolloids may easily be
brought to a more desirable contour by utility wax, This is done to prevent
a sag and distortion of the impression material.
May be used on the lingual portion of a bridge pontic to stabilize it while a
labial plaster splint is poured
The utility wax is usually supplied in both stick and sheet form in dark red or
orange color
19. Desirable Properties
Modelling wax:
Easy to mould when softened and NOT tear or flake
Easy to carve
Capable of being melted and solidified a number of times without change in properties
No residue to be left after lost wax technique
Inlay wax
Should have low thermal contraction
Correct flow properties
Good color contrast with oral tissues
Easy to carve without chipping
Burn out of mould without any residue
Should fracture rather than deform upon removal from cavity in case of an undercut
20. Methods of softening a wax
Water Bath
Flame of Bunsen burner
Infrared lamp
Wax annealer
21. Direct technique: Wax pattern is made directly in the oral cavity
Indirect technique: Wax pattern is made on a cast/die in lab outside the
oral cavity
22. THANKS !
For more on dental materials, Visit:
ourdentalmaterials.webs.com
