Laboratory Materials and Procedures

Copyright 2003, Elsevier Science (USA). All rights reserved.

Laboratory Materials and Procedures

Laboratory Materials and Procedures


IntroductionIntroduction Procedures that take place away from

the patient, take place in the dental laboratory.

Procedures that take place away from the patient, take place in the dental laboratory.


Uses of the Dental LaboratoryUses of the Dental Laboratory Pour up preliminary impressions. Trim and finish diagnostic models. Prepare custom trays. Polish:

• Provisional coverage• Partial or full dentures• Indirect restorations

Pour up preliminary impressions. Trim and finish diagnostic models. Prepare custom trays. Polish:

• Provisional coverage• Partial or full dentures• Indirect restorations


Laboratory RulesLaboratory Rules No eating, drinking, or smoking. Keep all cosmetics out of this area. Wear personal protective equipment when

working in the laboratory. Keep hair back. Report all accidents to the dentist immediately. Follow the manufacturer’s instructions for

equipment operation. Clean the work area before and after every

procedure.

No eating, drinking, or smoking. Keep all cosmetics out of this area. Wear personal protective equipment when

working in the laboratory. Keep hair back. Report all accidents to the dentist immediately. Follow the manufacturer’s instructions for

equipment operation. Clean the work area before and after every

procedure.


Safety in the LabSafety in the Lab Physical safety

• Know the location of the fire extinguisher and fire escape routes.

Chemical safety• Take care in the handling of corrosive,

toxic, or carcinogenic substances. Biohazards

• Items brought into the laboratory can also harbor blood and saliva that could be potentially infective.

Physical safety • Know the location of the fire

extinguisher and fire escape routes. Chemical safety

• Take care in the handling of corrosive, toxic, or carcinogenic substances.

Biohazards• Items brought into the laboratory can

also harbor blood and saliva that could be potentially infective.


Dental Laboratory Equipment Dental Laboratory Equipment Wall-mounted bins

• Used to store bulk supplies of plaster, stone, and investment materials.

Work pans • Open plastic containers with

identification labels used to hold laboratory work in progress.

Wall-mounted bins • Used to store bulk supplies of plaster,

stone, and investment materials. Work pans

• Open plastic containers with identification labels used to hold laboratory work in progress.


Dental Laboratory Equipmentcont’dDental Laboratory Equipmentcont’d Heat source

• A propane or butane torch or Bunsen burner is used for this purpose.

Model trimmer• A machine used to trim stone or

plaster models. Vacuum former

• Used to construct custom trays for bleaching, mouth guards, and positioners for orthodontics.

Heat source• A propane or butane torch or Bunsen

burner is used for this purpose. Model trimmer

• A machine used to trim stone or plaster models.

Vacuum former • Used to construct custom trays for

bleaching, mouth guards, and positioners for orthodontics.


Dental Laboratory Equipmentcont’dDental Laboratory Equipmentcont’d Vibrator

• Used to remove air bubbles and to aid in the flow of the plaster or stone when pouring diagnostic models.

Laboratory Handpiece• Low-speed handpiece used for

trimming custom impression trays, adjusting dentures, and polishing provisional and indirect restorations.

Vibrator • Used to remove air bubbles and to aid

in the flow of the plaster or stone when pouring diagnostic models.

Laboratory Handpiece• Low-speed handpiece used for

trimming custom impression trays, adjusting dentures, and polishing provisional and indirect restorations.


Dental Laboratory Equipmentcont’d Dental Laboratory Equipmentcont’d Sandblaster

• Hand-held unit that sprays sand at a high speed, creating an etching, or pitting, on a surface area of metal, porcelain, or acrylic.

Articulator• A machine that works as close as

practical to the way the mouth works.

Sandblaster • Hand-held unit that sprays sand at a

high speed, creating an etching, or pitting, on a surface area of metal, porcelain, or acrylic.

Articulator• A machine that works as close as

practical to the way the mouth works.


Dental Laboratory Equipmentcont’d Dental Laboratory Equipmentcont’d Dental lathe

• Used to polish or trim custom trays, provisional coverage, dentures, and indirect restorations.

Instruments• Wax spatulas• Mixing spatulas• Rubber bowls

Dental lathe • Used to polish or trim custom trays,

provisional coverage, dentures, and indirect restorations.

Instruments• Wax spatulas• Mixing spatulas• Rubber bowls


Dental Models 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.

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.


Use of Dental ModelsUse of Dental Models 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.

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.


Gypsum Products 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.

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.


Physical Forms of GypsumPhysical Forms of Gypsum Model plaster

• Commonly called plaster of Paris, is used primarily for pouring preliminary impressions and the making of diagnostic models.

Model plaster• Commonly called plaster of Paris, is

used primarily for pouring preliminary impressions and the making of diagnostic models.


Physical Forms of Gypsumcont’dPhysical Forms of Gypsumcont’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.

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.


Physical Forms of Gypsumcont’dPhysical Forms of Gypsumcont’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.

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.


Table 47-1: Recommended Ratios of Water to Powder for Gypsum ProductsTable 47-1: Recommended Ratios of Water to Powder for Gypsum Products


Pouring Dental Models Pouring Dental Models Model consists of two parts

• Anatomic portion, which is created from the alginate impression

• Art portion, which forms the base of the model

Model consists of two parts• Anatomic portion, which is

created from the alginate impression

• Art portion, which forms the base of the model


Different Pouring Methods Different Pouring Methods Double‑pour method

• The anatomic portion of the model is poured first. Then a second mix of plaster or stone is used to prepare the art portion.

Box‑and‑pour method• The impression is surrounded with a "box"

made of wax and poured as one unit. Inverted‑pour method

• Consists of mixing one large mixture of plaster or stone and pouring both portions of the model in a single step.

Double‑pour method• The anatomic portion of the model is

poured first. Then a second mix of plaster or stone is used to prepare the art portion.

Box‑and‑pour method• The impression is surrounded with a "box"

made of wax and poured as one unit. Inverted‑pour method

• Consists of mixing one large mixture of plaster or stone and pouring both portions of the model in a single step.


Trimming and Finishing of Dental Models Trimming and Finishing of Dental Models Prepare model

• Soak in water for at least 5 minutes. Trimming the maxillary model

• Trim the base.• Trim the posterior area.• Trim the sides.• Trim the heel cuts.• Trim the angled portion from canine to

canine.

Prepare model• Soak in water for at least 5 minutes.

Trimming the maxillary model • Trim the base.• Trim the posterior area.• Trim the sides.• Trim the heel cuts.• Trim the angled portion from canine to

canine.


Trimming and Finishing of Dental Modelscont’dTrimming and Finishing of Dental Modelscont’d Trimming the mandibular model

• Trim the posterior portion of the mandibular model until it is even with the maxillary model.

• Trim the base.• Trim the lateral cuts to match the

maxillary lateral cuts.• Trim the back and heel cuts.• Trim from canine to canine in a

rounded form.

Trimming the mandibular model • Trim the posterior portion of the

mandibular model until it is even with the maxillary model.

• Trim the base.• Trim the lateral cuts to match the

maxillary lateral cuts.• Trim the back and heel cuts.• Trim from canine to canine in a

rounded form.


Finishing the model • Mix a slurry of gypsum, and fill in

any voids. Polishing a plaster model

• Soak the model in a soapy solution for 24 hours.

• Dry, and then polish with a soft cloth.

Finishing the model • Mix a slurry of gypsum, and fill in

any voids. Polishing a plaster model

• Soak the model in a soapy solution for 24 hours.

• Dry, and then polish with a soft cloth.

Trimming and Finishing of Dental Modelscont’dTrimming and Finishing of Dental Modelscont’d


Custom Impression Trays Custom Impression Trays Criteria

• Be sufficiently rigid to hold and support the material during tray placement and removal.

• Fit and adapt well to the arch and maintain patient comfort.

• Provide accurate adaptation to an edentulous or a partially edentulous arch.

• Maintain an even distribution of 3 to 4 mm of the impression material between the tray and the teeth.

• Maxillary tray must cover the teeth and hard palate and extend slightly beyond the gingival margin.

• Mandibular tray must cover the teeth and extend beyond the gingival margin.

Criteria • Be sufficiently rigid to hold and support the

material during tray placement and removal.• Fit and adapt well to the arch and maintain

patient comfort.• Provide accurate adaptation to an edentulous or

a partially edentulous arch.• Maintain an even distribution of 3 to 4 mm of the

impression material between the tray and the teeth.

• Maxillary tray must cover the teeth and hard palate and extend slightly beyond the gingival margin.

• Mandibular tray must cover the teeth and extend beyond the gingival margin.


Table 47-2 Elements of a Custom Impression Tray Table 47-2 Elements of a Custom Impression Tray


Custom Tray Materials Custom Tray Materials Self-curing acrylic resin

• Provides a strong and easily adaptable material to create a custom tray. The major disadvantage of this material is the hazards of working with the liquid monomer, which is very volatile.

Self-curing acrylic resin• Provides a strong and easily

adaptable material to create a custom tray. The major disadvantage of this material is the hazards of working with the liquid monomer, which is very volatile.


Custom Tray Materialscont’dCustom Tray Materialscont’d Light-cured resin tray materials

• A premixed, prefabricated light-cured tray material that does not contain methylmethacrylate monomer. The properties of this material provide excellent adaptation of the model, and may be used for any impression situation: dentulous, edentulous, or partially edentulous.

Light-cured resin tray materials • A premixed, prefabricated light-cured

tray material that does not contain methylmethacrylate monomer. The properties of this material provide excellent adaptation of the model, and may be used for any impression situation: dentulous, edentulous, or partially edentulous.


Custom Tray Materialscont’dCustom Tray Materialscont’d Vacuum-formed thermoplastic resin

• A vacuum former uses heat and vacuum to shape a sheet of thermoplastic resin to a diagnostic model.

Vacuum-formed thermoplastic resin • A vacuum former uses heat and

vacuum to shape a sheet of thermoplastic resin to a diagnostic model.


Dental WaxesDental Waxes 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.

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.


Dental Waxes cont’dDental Waxes cont’d Utility wax

• Supplied in different forms depending on its use.

• Its makeup is beeswax, petrolatum, and other soft waxes.

• Uses: 1.Extend the borders of an

impression tray. 2.Cover brackets in orthodontic

treatment.

Utility wax • Supplied in different forms depending

on its use.• Its makeup is beeswax, petrolatum,

and other soft waxes.• Uses:

1.Extend the borders of an impression tray.

2.Cover brackets in orthodontic treatment.


Dental Waxes cont’dDental Waxes cont’d Sticky wax

• Supplied in sticks or blocks.• Main ingredients are beeswax and

rosin. • Very brittle wax, but when heated, it

becomes very tacky.• Useful when creating a wax pattern or

joining acrylic resin together.

Sticky wax• Supplied in sticks or blocks.• Main ingredients are beeswax and

rosin. • Very brittle wax, but when heated, it

becomes very tacky.• Useful when creating a wax pattern or

joining acrylic resin together.


Dental Waxes cont’dDental Waxes cont’d Inlay casting wax

• Hard brittle wax made from paraffin wax, carnauba wax, resin, and beeswax.

• Used to create a pattern of the indirect restoration on a model.

• Classified according to how they flow:1.Type A: Hard-inlay wax.2.Type B: Medium-inlay wax.3.Type C: Soft-inlay wax.

Inlay casting wax • Hard brittle wax made from paraffin

wax, carnauba wax, resin, and beeswax.

• Used to create a pattern of the indirect restoration on a model.

• Classified according to how they flow:1.Type A: Hard-inlay wax.2.Type B: Medium-inlay wax.3.Type C: Soft-inlay wax.


Dental Waxes cont’dDental Waxes cont’d Casting wax

• Makeup is paraffin, ceresin, beeswax, and resins.

• Supplied in sheets of various thicknesses.

• Used for single-tooth indirect restorations, fixed bridges, and casting metal portions of a partial denture.

Casting wax • Makeup is paraffin, ceresin, beeswax,

and resins. • Supplied in sheets of various

thicknesses. • Used for single-tooth indirect

restorations, fixed bridges, and casting metal portions of a partial denture.


Dental Waxes cont’dDental Waxes cont’d Baseplate wax

• 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.

Baseplate wax • 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.


Dental Waxes cont’dDental Waxes cont’d Bite registration waxes

• Soft and very similar to casting waxes.

• Softened under warm water.• Patient is instructed to bite down, and

the wax will form an imprint of the teeth.

Bite registration waxes • Soft and very similar to casting

waxes.• Softened under warm water.• Patient is instructed to bite down, and

the wax will form an imprint of the teeth.

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Laboratory Materials and Procedures