Transcript Laboratory Materials and Procedures

Chapter 47
Laboratory Materials and
Procedures
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Produced in the United States of America
ISBN 0-7216-9770-4
Copyright 2003, Elsevier Science (USA). All rights reserved.
Dental Models

Three-dimensional reproductions of the
teeth and the surrounding soft tissue of a
patient’s maxillary and mandibular arches.
Also referred to as study casts.
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Use of Dental Models
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Diagnosis for a fixed or removable prosthetic.
Diagnosis of orthodontic treatment.
Visual presentation of dental treatment.
Making of custom trays.
Making of orthodontic appliances.
Making of provisional coverage.
Making of mouth guards.
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Dental laboratory materials
 Several materials
 Will study
• Gypsum materials
• Dental waxes
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Gypsum Products
 Used extensively in dentistry to make dental

models.
Chemical properties
• A mineral that is mined from the earth.
• In its unrefined state, gypsum is the
dihydrate form of calcium sulfate.
• Converted into a powdered hemihydrate.
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Classification
Gypsum product
Impression plaster (type 1)
Plaster (type 2)
High strength plaster
Stone (type 3)
High-strength stone( type 4)-Die stone
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Physical Forms of Gypsum
 Model plaster
• Commonly called plaster of Paris, is used
primarily for pouring preliminary
impressions and the making of diagnostic
models.
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Physical Forms of Gypsum-cont’d
 Dental stone
• For use as a working model when a more
durable diagnostic cast is required.
Examples are in the making of custom
trays and orthodontic appliances.
Model made of dental stone
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Physical Forms of Gypsum-cont’d
 High-strength stone
• Also known as densite or improved dental
stone. Its strength, hardness, and
dimensional accuracy make it ideal to
create the dies used in the production of
crowns, bridges, and indirect restorations.
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Table 47-1: Recommended Ratios of Water to
Powder for Gypsum Products
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Dental Waxes
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Dental waxes
Pattern
Processing
Impression
Inlay
boxing
corrective
Resin
Sticky
Bite registration
Casting
Carding
Base plate
Block out
White
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utility
Dental Waxes - cont’d
 Baseplate wax
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Made from paraffin or ceresin with beeswax and
carnauba wax.
Hard and brittle at room temperature.
Supplied in sheets.
Three types:
1. Type I, which is a softer wax used for denture
construction.
2. Type II, a medium-hardness wax used in
moderate climates.
3. Type III, a harder wax for use in tropical
climates.
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Base plate Wax-contd
 Uses:
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 Used to make wax rims for edentulous patients
 To wax-up teeth in partial and full dentures
 Used to create a spacer over the cast before
custom trays can be made.
 As a block-out wax for undercuts on casts.
 At times used for bite registration
Presentation:
 It is available in sheet and ribbon form and is
pink in color
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Bite Registration Wax
 Bite registration wax is a metal-impregnated wax
in sheet form.
 Patient is instructed to bite down, and the wax will form an
imprint of the teeth.
 Use:
 It is used to record the occlusal relationships
between a patient's opposing arches and
to later transfer this relationship to the cast for
articulation.
 Often without this record, it is impossible for the dentist or the
laboratory technician to properly occlude the patient's cast.
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Casting wax
 Makeup is paraffin, ceresin, beeswax, and
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resins.
Supplied in sheets of various thicknesses.
Used:
Used for single-tooth indirect
restorations, fixed bridges, and casting
metal portions of a partial denture
Used for thin sections of certain partial
denture and crown and bridge patterns.
They are convenient in the preparation
of copings or clasps requiring
uniformly thin regions
Inlay wax
 Uses:
 For the preparation of inlay partners, crowns,
bridges using the lost wax technique. Either
in the mouth by direct technique or on a
model or die cast which is cast out from an
impression
 For wax up procedures-diagnostic wax up
 Properties
 Have low thermal conductivity
 Have the correct flow properties
 Should be colored usually blue or green i.e. to
contrast with oral tissues
 Should be easy to curve without flecking or
chipping
 Shouldn't leave any residue on the mould.
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Carding and boxing in wax
Boxing wax
 Soft pliable wax with a smooth and shiny appearance.
 Supplied in long narrow strips measuring 1 to 1½
inches wide and 12 to 18 inches long.
 Used to form a wall or box around a preliminary
impression when pouring it up
 Properties
 Has high flow valve at room temperature
 Its easily molded without the need of heating
Carding wax
 Uses:
 Used by manufacturers to attach artificial teeth to
the mounts on which are supplied.
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Sticky Wax
 Supplied in sticks or blocks.
 Main ingredients are beeswax paraffin, and resin.
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The resin gives the wax its adhesiveness and hardness.
Colors are orange and the darker shades of blue, red,
and violet
Very brittle wax, but when heated, it becomes very tacky.
An important requirement of sticky wax is that it must break
under pressure rather than bend or distort.
Use:
This property makes it useful for holding the parts of a
broken denture together so that it can be repaired.
Useful when creating a wax pattern or joining acrylic resin
together.
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Utility Wax
 Supplied in different forms depending on its use. May be red or
colorless wax that comes in rope form
 Its makeup is beeswax, petrolatum, and other soft waxes.
 It is extremely pliable and tacky at room
temperature, making it usable without heating.
 Use:
 Extend the borders of an impression tray.
Main use is in beading (curbing) impressions before boxing and
pouring.
 It can also be used on the impressions trays to avoid the flow of
impression material to the back of the throat and to avoid injury
to the soft tissue
 Cover brackets in orthodontic treatment
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Indicator Wax
 Indicator wax is usually green in color and is
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coated with a water soluble adhesive on one side.
Use:
It is used for registering occlusal contacts on
natural teeth, individual restorations, FPDs,
RPDs, and CDs.
 It is sometimes used by the dentist to evaluate
high spots on restorations.
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