Transcript Performance of dental materials

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 thermoplastic molding material.
 solid at room temperature.
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- Baseplate wax: sheets, establish initial arch
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form in construction of CD.
Bite wax: record the occlusal surfaces of teeth.
Boxing wax: sheet wax used as a border of an
impression to provide base of the cast to be
made.
Inlay wax: applied to dies to form direct or
indirect patterns for the lost-wax tech.
Sticky wax: adheres to dry clean surfaces.
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 BASE Wax: that is almost always paraffin (not smooth,
not glossy, flake when trimmed)
(1)
Hydrocarbon of paraffin or esters
(2)
High or low MW
 MODIFIER Waxes: contribute properties such as
increased hardness, stickiness, or brittleness
(1) Hydrocarbon or ester types;
(2) High or low MW
 COLORANT: 1%
 Fillers: some waxes contain it to control
expansion and shrinkage of the wax product.
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Natural (mineral, vegetable, or animal origin and/or
synthetic waxes (more homogeneous & pure)
Natural waxes are complex combinations of organic
compounds of high molecular weight:
 Hydrocarbons,e.g. saturated alkanes, & microcrystalline
wax series, carnauba wax, candelilla wax.
 Esters, e.g.myricylpalmitate.
Some waxes also contain free alcohol and acid.
(Esters are formed from union of higher fatty acids with
higher aliphatic alcohol with elimination of water)
Alcohol+Fatty Acid Ester+Water
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Natural waxes
Synthetic waxes Additives
Minerals: Paraffin
Acrawax C
Aerosol,OT
Castorwax
Flexowax C
Epolene N-10
Albacer
Aldo 33
Durawax 1032
Microcrystalline
Barns Dahl
Ozokerite
Ceresin
Montan
Plants :Carnauba
Ouricury
Candelilla
Japan wax
Coca butter
Insect: Beeswax
Animal: Spermaceti
Fats
Stearic acid
Glyceryltristearate
Oils
Turpentine
Color
Natural Resins
Rosin
Copal
Dammar
Sandarac
Mastin, Shellac
Kauri
Synthetic Resins
Elvax
Polyethylene
Polystyrene
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 Gum dammar: smoothness, resistant to
flaking, toughness. (resin)
 Ceresin the hardness and water resistance of
wax. Improves carving properties.
 Carnuba the hardness and water resistance,
melting range, gives glossiness, flow at
mouth temp.
 Beeswax the stickiness, improves flow
properties at mouth temperature. (esters)
 Rosin the brittleness. (resin)
 Microcrystalline waxes stress release on
cooling.
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 Occurs because of the Multiple wax mixtures
 The liquidus line (representing the temperature at
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which complete melting has occurred)
The solidus line (below which the composition is
entirely solid)
the solid + liquid range in between is quite broad
(almost 40°C). To allow manipulation
To develop wax flow, the temperature only needs to
be heated to a point within the solid+liquid range
or up to the point of the liquidus line but not much
higher.
Excessive heating would cause decomposition.
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TEMPERATURE (C)
LIQUID
90
Melting Completion (Liquidus)
80
70
LIQUID + SOLID
60
50
40
Melting Onset (Solidus)
30
SOLID
20
25
Paraffin
50
COMPOSITION (%)
75
100
Carnuba
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Name:
Origin:
PARAFFIN
Composition:
Melting
(C)
Density
(20C)
Mineral Hydrocarbon mixture
50-57
0.90
CERESIN
Mineral Complex hydrocarbons
61-78
0.91-0.92
BEESWAX
Animal
Ester mixture
62-65
0.95-0.96
CANDELILLA
Plant
C21 hydrocarbons
68-70
0.95-0.99
CARNAUBA
Plant
Hydrocarbon, Ester, Fatty
Acid
82-86
0.99-0.999
GUM
DAMMAR
Plant
Aromatic resin
ca 120
1.0401.120
ROSIN
Plant
Aromatic resin acid
100-150
1.08
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Methods:
1. Flame heated instruments
2. warmth of hand??
3. dry heat as wax pot
4. Water bath, but not for inlay wax??
Flow :
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after the highest melting point is reached.
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Temperature  1/ viscosity
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Flow temperature must be > mouth temp if needed in
solid state
Over heating should be avoided?
the base or modifier waxes can be decomposed.
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 In solids its analogous to creep
 In liquids its analogous to viscosity
 Waxes are usually non-flowable at room temperature
 Temperature  1/ viscosity
 It is critical for inlay wax to have flow less than 1%
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 It is low
 Wax should be softened evenly by
 rotation above the flame until it evenly softens or
flows
 Tempered in a water bath alternately with the flame
heating to allow the core to soften before dripping
 If a soft core of a bulk of wax is to be made, roll the
wax when it is in softened status – (unable to hold
shape by itself)
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 Used with cast metal techniques
 Wax patterns need to be burned to the
point where no excess residue may
interfere with metal casting
 Heat melt and/or decompose wax by the
process of oxidation which completely
transform it into water vapor and carbon
dioxide so that no residue is left.
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 Created by the bees wax addition
in the mixture
 Increased if material is warmed by
hand
 Solid waxes become tacky to other
material if heated
 Adhesives may be applied on casts
before wax application
 Wax dipping in bees wax increase
stickiness of refractory casts
 Old wax adheres to new one if
surface is dry
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Wax should be dimensionally stable
once it has solidified (less than 1%).
 Invest the pattern immediately after
removal from the die.
Deformations:
Plastic deformation
 Under force is by ductility.
 Ductility allows it to be carved
or burnished
Residual stress recovery
Elastic Recovery
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Residual stress reduction
 Heat material evenly
 Follow manufacturer instructions
 Invest within 30 min of carving
 Whenever wax additions are cooled. The
exterior surface tends to cool first. The molten
interior slowly solidifies and contracts. This
encourages distortion or flow. Add in small
increments, layering
 Store at low temperatures
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Very high
 ceramics (1-15 ppm/°C)
 metals (10-30 ppm/°C)
 waxes (30-600 ppm/°C)
 inlay wax (250-300 ppm/°C)
( wax pattern made in the mouth
will shrink appreciably)
Residual thermal stresses may change
Do not
heat
above
melting
point
during
work
dimensions
Paraffin > beeswax >carnuba
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250
ppm/C
1.2
EXPANSION (%)
KERR
HARD
WAX
1.0
0.8
0.6
0.4
0.2
0
0
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30
35
40
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TEMPERATURE (C)
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 Wax is hydrophobic
 To increase its wetting a surfactant could be sprayed
over wax to increase flow of investment material
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 Coloring is not standardized
 Dark colors provide good color contrast for processing
wax
 Opaque and Tooth-colored waxes provide good
material for esthetic case presentations and patient
education
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Uses
metal castings of
 Inlays
 Attachments
 Crowns
 Pontics
 Partial dentures
 Denture base material
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Forms
sticks pallets, tins
-Blue or green
Consistencies
Removable
Die with
Waxed Inlay
-Hard, medium, soft, regular
Application
-indirect and direct technique
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Composition
Paraffin + Carnuba + Ceresin
+Beeswax + Colorants
Properties
- low thermal dimensional change
- flow temp higher than mouth
- must have clean excess residue
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Application
Used for metal framework
complete and partial dentures
Forms
Sheets and preformed shapes
Properties
low thermal dimensional change
must have clean excess residue
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Form
sheets
Types I, II & III
Application
-wax registration of ridge form
-Carved into tissue forms and Support teeth
-Bite registration
Properties
-melting range higher than mouth temperature
-Customised to climate
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Uses
 For edentulous impressions
 Corrects undercuts
 Closes bubbles
Properties
 flow at mouth temperature
 E.g. Bite wax, mizzy
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Uses
 To articulate models
correctly
Forms
 horse shoe shape
 May be supported by
metal foil for stability
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Forms
1 inch sheets
Uses
used to form base of the cast pouring
May be used to modify borders of trays
Properties
Tacky at room temp
Transfer to impression
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Forms
Ropes manipulated at room temp
Applications
Add to the tray
- customize for pt mouth
- Comfort from sharp edges
- Control imp material in mouth
-Cover ortho bands and wires
- to register the bite
-Block out undercuts
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Forms
Pencil shape
orange or yellow
Properties
hard and brittle – can reorient if
broken
Adhere temporarily the metal,
gypsum, resin – for fabrication or
repair
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Thank you
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