Dental Models and Laboratory Materials

Anatomic Portion

• The structural part of a dental model created from an alginate impression.

Articulator

• A dental laboratory device that simulates mandibular and temporomandibular joint movement when models of the dental arches are attached to it.

Die

• An accurate replica of the prepared portion of a tooth, used in the laboratory during the fabrication of a cast restoration.

Dihydrate

• Related to gypsum products, indicating two parts of water to one part of calcium sulfate.

Dimensionally Stable

• Resistant to changes in width, height, and length.

Face Bow

• A portion of the articulator used to measure the upper teeth compared with the temporomandibular joint.

Gypsum

• A mineral used in the formation of plaster of Paris and stone.

Hemihydrate

• Removal of water to become one-half part water to one part of calcium sulfate, forming the powder product of gypsum.

Homogenous

• Having a uniform quality and consistency throughout.

Lathe

• A machine used for cutting or polishing dental appliances.

Model

• A replica of the maxillary and mandibular arches made from an impression.

Monomer

• A molecule that, when combined with other molecules, forms a polymer.

Nuclei Crystallization

• A chemical process in the setting of dental stone and plaster, in which a cluster of crystals interlink, giving strength and rigidity.

Polymer

• A compound of many molecules.

Slurry

• A mixture of gypsum and water used in the finishing of models.

Volatile

• A substance that can evaporate easily and is very explosive.

Equipment

• Vibrator: Used to remove air from the mix of gypsum products.

• Lathe: Used to polish dentures.

Types of Gypsum

• Model Plaster: Commonly referred to as plaster of Paris.

• Dental Stone: Used as a working model for making dentures.

Water/Powder Ratio for High-Strength Stone

• Recommended ratio: 100 g powder / 19-24 mL water.

Pouring Procedure

• Gypsum material should be placed on the most posterior tooth to flow to all areas of the impression.

Evaporation and Explosion

• Volatile describes something that evaporates easily and is very explosive.

Types of Wax

• Boxing Wax: Used to form a wall around a preliminary impression.

• Type B Inlay Wax: Used for indirect wax patterns on dies.

• Utility Wax: Used to cover orthodontic brackets.

Dental Laboratory

• The dental laboratory is a separate area of the dental office, away from the patient treatment area, where the dentist and clinical staff complete the following procedures:

  • Pour preliminary impressions.

  • Trim and finish diagnostic models.

  • Prepare custom trays.

  • Polish provisional, partial, and full dentures, and indirect restorations.

• Specialty practices (fixed and removable prosthodontics, orthodontics, and pediatrics) will have a more extensive laboratory due to higher demands of laboratory work.

• Having laboratory equipment available allows the dentist and dental assistant to handle case work without sending it to a private dental laboratory, minimizing overhead costs.

• If a case cannot be completed in the dental office laboratory, it will be sent to a commercial dental laboratory.

Safety in the Dental Laboratory

• Safety must be the first concern.

• Follow safety precautions and infection control procedures.

• Items brought into the laboratory from the treatment room are contaminated, making exposure control important.

Physical Safety

• Become familiar with the location of the fire extinguisher and fire escape routes.

• Keep all equipment in good working order and follow the manufacturer's directions.

Chemical Safety

• Dental materials may include corrosive, toxic, or carcinogenic substances.

• Avoid direct contact with chemicals that could be inhaled, absorbed, or ingested.

Biohazards

• Impressions and other items can harbor blood and saliva that can be infectious.

• The laboratory area and contaminated items must be disinfected before and after each use.

Laboratory Rules

• OSHA describes the dental lab as dangerous if rules and standards are not followed.

  • Materials and equipment can pose a hazard to being inhaled, affecting eyes and skin, and harming the machinery.

  • Follow infection control/OSHA guidelines for handling all dental materials and laboratory equipment.

  • No eating, drinking, or smoking is permitted.

  • Wear personal protective equipment (PPE) when working in the lab.

  • Never work in the lab without proper eye protection.

  • Keep hair pulled back.

  • Report all accidents to the dentist immediately.

  • Follow the manufacturer's instructions for equipment operation.

  • Turn off all equipment before leaving the lab.

  • Clean the work area before and after every procedure.

Dental Laboratory Equipment

• The dental laboratory includes a countertop and cabinets for workspace and storage.

• Wall-mounted bins are used to store bulk supplies of plaster, stone, and investment materials.

  • These bins protect materials from moisture contamination.

  • Replace the cover immediately after material is retrieved.

• Work pans are open plastic containers with identification labels, used to hold laboratory work in progress.

  • Pans may be color-coded to indicate the type of procedure.

Heat Sources

• A heat source is required to heat wax or other materials.

  • A propane or butane torch is used.

  • If a gas line is installed, use rubber hosing attached to a Bunsen burner.

  • Turn the handle completely on or off to prevent gas leaks.

Model Trimmer

• The model trimmer is used to trim stone or plaster models.

  • It has an abrasive grinding wheel, which should be kept clean.

  • Models are held in place by hand or with a holding device.

  • A gentle stream of water continuously runs on the wheel to control dust and facilitate cutting.

  • Used water drains into a sink equipped with a plaster trap to prevent clogging.

Vacuum Former

• The vacuum former is a small electrical appliance used to construct custom trays for:

  • Bleaching

  • Mouth guards

  • Surgical templates

  • Positioners for orthodontics

  • The upper part of the unit heats and softens a sheet of thermoplastic resin.

  • The work surface has holes to allow the vacuum to pull and shape the warmed plastic around the model.

Dental Vibrator

• The dental vibrator is used to remove air from the mix of plaster or stone and to aid in the flow of material when a diagnostic model is poured.

  • It has a flat working surface that vibrates the bowl or tray.

  • A disposable cover can be placed on the work surface for cleanliness.

Laboratory Handpiece

• A low-speed laboratory handpiece is used for:

  • Trimming custom impression trays

  • Adjusting dentures

  • Polishing provisionals

  • Indirect restorations

Sandblaster (Air-Abrasion)

• A sandblaster is a handheld unit that sprays sand at a high rate of speed, creating an etching or pitting on a surface area of:

  • Metals

  • Porcelain

  • Acrylic

  • These elevations create added retention through surface roughening.

  • Sandblasting is suitable for the repair of:

    • Crowns

    • Dentures

    • Appliances

    • For the cementation of crowns, bridges, and inlays.

Articulator

• An articulator is a mechanical device used in dentistry to hold maxillary and mandibular dental models in a position to aid in reproduction of the mandible in relation to the maxilla.

  • It allows the movement of the mandible and TMJ on mounted models.

  • The articulator allows the dentist and dental laboratory technician to fabricate:

    • Removable prosthodontic appliances (dentures)

    • Fixed prosthodontic restorations (crowns, bridges, in-lays, and onlays)

    • Orthodontic appliances

  • Special records are taken to position the dental models accurately on the articulator.

  • CAD/CAM technology can simulate articulation by using an intraoral scanner to digitize the dental arches.

    • This provides another way to record the maxillomandibular relationship.

  • A complete digital workflow will require the use of a digital articulator for occlusion analysis.

Face Bow

• The face bow determines the positional relationship of the maxillary arch to the temporomandibular joints.

  • The centric relation or bite record is a measurement of where the teeth are positioned when the joints are aligned correctly and before the teeth come in contact.

  • This provides information to construct dental prosthetic fixed and removable appliances such as dentures, partials, crowns, and bridges.

  • In some states, credentialed dental assistants can perform the technique for taking a face bow registration.

Dental Lathe

• The dental lathe is used to trim and polish custom trays, provisional coverage, dentures, and indirect restorations.

  • It has a protective plastic see-through shield.

  • Revolving threaded extensions from each end of the electric motor attach attachments such as an abrasive grinding wheel, bur chucks, or a rag wheel.

  • After each use, attachments must be sterilized before reuse.

  • Pumice and other polishing agents are used during polishing.

  • A protective pan behind and under the wheel holds the pumice and catches the spatter.

Specialized Spatulas and Bowls

• Specialized instruments must be sterilized and stored properly after each use.

  • A wax spatula is a double-ended instrument used in waxing a pattern or when working with wax for a partial or a full denture.

    • The #7 wax spatula is used most often in the laboratory.

  • The type of spatula chosen depends on the strength of the dental material being mixed.

• Rubber bowls are used for mixing alginate in the treatment area and for mixing stone or plaster in the laboratory setting.

  • Ensure an adequate supply of rubber bowls.

Dental Models/Study Casts

• Dental Models/ study casts, are a reproduction of the teeth and surrounding soft tissues of the patient's maxillary and mandibular arches

• A model is created by using an alginate impression.

  • The alginate impression is taken to the laboratory and then poured into a gypsum product to create the completed model.

  • These models show a 3D view of conditions, providing a valuable diagnostic tool.

  • The dentist can use a dental model to analyze the patient's mouth from viewpoints that are impossible to evaluate from the clinical examination.

• Dental models are used for the following procedures in dentistry:

  • Diagnosis for planning a fixed or removable prosthetic device

  • Diagnosis of orthodontic treatment

  • Visual presentation of dental treatment

  • Production of custom trays

  • Creation of orthodontic appliances

  • Making of provisional coverage

  • Making of mouth guards

Gypsum Products

• Gypsum products are used extensively in dentistry to construct dental models.

  • Many characteristics and properties affect the use of gypsum.

Chemical Properties

• Gypsum is a mineral mined from the earth.

  • In its unrefined state, gypsum is the dihydrate form of calcium sulfate, consisting of two parts water to one part calcium sulfate.

  • When gypsum is heated during the manufacturing process, the water is removed, and the gypsum is converted into a powdered hemihydrate, which consists of ½ part water to one part calcium sulfate.

Setting Reactions

• When mixing a gypsum powder with water, the hemihydrate crystals dissolve in the water to form clusters known as the nuclei of crystallization.

  • These nuclei are so close together that as the gypsum crystals expand during the setting process, they intermesh and become entangled with each other.

  • As more intermeshing of crystals occurs, the strength, rigidity, and hardness of the final product is increased.

Forms

• The American Dental Association (ADA) has classified gypsum into five types of products because of their chemical property and strength.

  • The only differences between these are the size, shape, and porosity of the hemihydrate crystals.

  • Differences in the strength of the hemihydrate crystals are accomplished by changing the water-to-powder ratio for each type of gypsum product.

Impression Plaster (Type I)

• Model plaster is white and used primarily for pouring preliminary impressions for the fabrication of an edentulous model and diagnostic study models for case presentation and in the use of orthodontics

Model Plaster (Type II)/Plaster of Paris

• Model plaster is white and used primarily for pouring preliminary impressions for the fabrication of an edentulous model and diagnostic study models for case presentation and in the use of orthodontics.

  • The crystals in plaster are irregularly shaped and very porous, similar in appearance to a sponge.

  • Because of the porous and irregular crystals, model plaster requires the greatest quantity of water for mixing, which produces the weakest form of a study model.

Dental Stone (Type III)

• Dental stone is a form of gypsum that is typically yellow and is used when a more durable diagnostic cast is required, or when a working model is needed for the fabrication of fixed or removable prosthetics, retainers, and custom trays.

  • The crystals in dental stone are more uniform in shape and less porous than those in plaster.

  • The result is a study model that is much stronger and denser than one made from plaster.

Die Stone (Type IV)

• Also known as densite, or improved dental stone die stone has a strength, hardness, and dimensional accuracy that make it ideal for use by the dental laboratory technician in creating a die for use in the fabrication of a wax pattern with the production of crowns, bridges, and indirect restorations.

High-Strength Stone (Type V)

• This stone is the strongest, with the least amount of expansion.

  • The crystals in high-strength stone are smooth and very dense and require the least amount of water for mixing but have more expansion than type VI stone.

  • It was designed for the newer alloys used in dentistry that have more shrinkage of the casting.

  • It is not recommended to use in the fabrication of inlays and onlays because of creating too tight of a casting fit.

Powder-to-Water Ratio

• The powder-to-water ratio has a significant effect on the setting time and strength of the gypsum product.

  • Each gypsum material has an optimal ratio as specified by the manufacturer.

  • These ratios should be observed carefully because deviations can change the consistency of the material and the properties of the set cast.

• Model plaster (type II):

  • $100 \, g$ powder to $45-50 \, ml$ water

• Dental stone (type III):

  • $100 \, g$ powder to $28-30 \, ml$ water

• Die stone (Type IV):

  • $100 \, g$ powder to $19-24 \, ml$ water

• When too little water is used, the mix will be dry, which will provide a shorter working time.

  • If additional water is added to thin the mixture, the crystallization (setting) process will be distributed, and the model will not have the desired strength

• When too much water is used, the mix will be thin and runny and will take longer to set; this creates a model that is considerably weaker.

  • If additional powder is added after the stirring has begun, continued stirring will break up the crystals that have begun to form.

  • The result is a cast that is weak and brittle.

• Measurements of the powder and water in each mix must be exact.

  • The water is measured by volume with a measuring device such as a large syringe or a milliliter-graduated cylinder.

  • The powder is measured by weight with the use of a scale.

  • Remember to adjust the scale for the recommended weight before the powder is weighed.

  • If a scale is not available, the powder may be measured by volume.

Pouring Dental Models

• A model consists of two parts:

  • The anatomic portion, which is created from the alginate impression, which includes the teeth, the mucosa, and the frenum attachments.

  • The art portion, which forms the base of the cast, is trimmed with specific angles.

  • When the models are trimmed and in occlusion, they are approximately 3 inches in overall height.

• Three different pouring methods can be used to create the base or art portion of the cast:

  • Double-Pour Method

    • The anatomic portion of the cast is poured first.

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

    • A free-form base may be created by hand, or a commercial rubber mold can be used.

  • Box-and-Pour Method

    • The impression is surrounded with a "box" made from boxing wax.

    • The completed box should extend at least 1 inch above the palatal area of the maxillary impression and 1 inch above the tongue area of the mandibular impression.

  • Inverted-Pour Method

    • The inverted-pour approach consists of mixing one large mixture of plaster or stone and pouring the impression first, then placing a base of material on a tile or counter to invert the impression in a single step.

    • This is the most common way of pouring an impression.

Trimming and Finishing Dental Models

• Models must have a professional appearance when used for a case presentation or as part of the patient's permanent record.

  • This is accomplished by trimming the models to a geometric standard.

  • The wax bite registration is used to articulate casts during the trimming process.

Anatomic and Art Portions

• The anatomic portion of the dental model includes the teeth, oral mucosa, and muscle attachments.

  • This portion makes up two-thirds of the overall trimmed cast.

• The art portion of the model forms the base and should make up one-third of the overall trimmed cast.

Polishing Plaster Models

• It is important for the model to have a professional-quality appearance.

  • To create a more polished look for a plaster model, soak the model in a soapy solution for 24 hours, allow to dry, and then polish with a soft cloth.

  • An alternative to this solution is a commercial model gloss spray that can be used for the same purpose.

Digital Models

• Many dental offices are replacing conventional plaster diagnostic models with three-dimensional (3D) imaging.

  • Digital models have taken an important place in the diagnosis and treatment of dental cases.

  • Digital models provide an excellent presentation tool to help patients visualize and understand a procedure or type of treatment, such as in orthodontics.

  • This type of technology integrates information from digital and photographic images to be a part of a treatment plan.

  • Various studies have confirmed digital models constructed by scanning technology are extremely accurate and an easy task for dental assistants to perform, once trained.

• Advantages of using digital models over traditional models include:

  • Little physical storage space required

  • Easily accessible anywhere to complete the patient's treatment plan

  • Easily duplicated at no cost

  • Unbreakable

  • Impossible to misplace

  • Require no laboratory setup compared to conventional plaster study models.

Custom Impression Trays

• Custom impression trays are made specifically for an individual patient.

  • They are created in the dental laboratory within the office, or a dental laboratory technician can prepare these before the patient returns for his or her appointment.

Criteria for Creating Custom Impression Trays

• Tray must be sufficiently rigid to hold and support materials needed during tray placement and removal.

• Tray must fit and adapt well to the arch and must maintain patient comfort without impinging (pressing uncomfortably) on surrounding tissues.

• Tray must provide accurate adaptation to an edentulous or partially edentulous arch.

• Tray must maintain an even distribution of 3 to 4 mm of impression material between itself and the teeth.

• The completed maxillary tray must cover the teeth and hard palate and extend slightly beyond the gingival margin (but not into the mucobuccal fold).

• The completed mandibular tray must cover the teeth and extend beyond the gingival margin (but not into the mucobuccal.

• The primary materials that can be used to construct custom trays are self-curing acrylic resin, light-cured resin, and thermoplastic material.

  • Regardless of the material used, a diagnostic model must be prepared first, in accordance with specific guidelines.

Guidelines and Terminology for Creating a Custom Impression Tray

• Undercuts:

  • The first step in cast preparation is to fill all undercuts with wax or other molding material.

  • Air bubbles in the cast, the shape of the arch and ridge, carious lesions, fractured teeth, and deep interproximal spaces and malposed teeth may cause undercuts.

• Outlining the tray:

  • The margins of the cast where the finished tray will be seated are outlined in pencil.

  • The outline, which designates the area to be covered by the tray, extends over the attached gingiva to the mucogingival junction and 2 to 3 mm beyond the last tooth in the quadrant.

• Spacer:

  • A spacer is placed on the cast to create room in the tray for the impression material.

  • Baseplate wax, a folded moist paper towel, or a commercial nonstick molding material may be used for this purpose.

  • To create the spacer, cut a length of baseplate wax, warm it, and place it on the cast over the area of the tray.

  • A warmed plastic instrument is used to lute the wax to the cast.

• Spacer stops:

  • Spacer stops are placed to prevent the tray from seating too deeply onto the arch or quadrant.

  • Spacer stops also allow for an adequate quantity of impression material around the preparations.

  • Spacer stops are triangular or round holes that are cut out of the spacer with a laboratory knife or wax spatula.

  • These cutouts will form bumps on the tissue side of the tray. (The tissue side is the inner surface of the completed tray.)

  • An edentulous tray requires a minimum of four stops: one each on the crest of the alveolar ridge in the area of the first or second molar.

  • Additional stops may be placed on the crest of the ridge in the area of each canine.

  • A tray used to take an impression of prepared natural teeth, as for a crown or a bridge, has the stops placed near, but not on, the prepared teeth.

• Separating medium:

  • The prepared cast, spacer, and immediate surrounding area are painted with a separating medium so that the completed tray can be separated readily from the cast.

• Handle:

  • A handle adapted to the tray will allow easier placement into and removal from the patient's mouth.

  • The handle is always placed at the anterior of the tray, as near the midline as possible, facing outward and parallel to the occlusal surfaces of the teeth.

  • The handle is formed from a piece of scrap acrylic that was cut away from the tray.

  • The end of the handle and the area where it will be attached to the tray are moistened with tray resin liquid.

• Spacer removal:

  • After the tray has been formed, it is necessary to remove the spacer and clean the tissue side of the tray.

  • A small, stiff brush, such as a toothbrush, is used to remove most of the wax at this time.

  • The remainder of the spacer is re-moved, and the interior of the tray is cleaned after the tray reaches its final set.

• Finishing:

  • It is not necessary to remove rough areas on the tissue side of the tray; this surface will be covered with impression material.

  • If the outer edges of the tray are rough, however, it is necessary to smooth them so they do not injure the tissues of the patient's mouth.

  • A laboratory knife can be used to smooth minor rough areas.

  • An acrylic bur in a straight slow- speed handpiece can be used to remove major rough areas.

  • An alternative is to use the laboratory lathe to smooth the edges.

  • The tray is given a final rinse and is disinfected according to the manufacturer's instructions.

Acrylic Resin Tray Materials

• Self-curing acrylic resin provides a strong and easily adaptable material that can be used to create a custom tray.

  • The major disadvantage of this material involves the hazards of working with the liquid monomer, which is highly volatile.

  • The vapor is highly flammable, is hazardous if inhaled in large concentrations, and may be irritating to the skin.

  • This material must be handled with great care and proper ventilation must be used.

• When a self-curing resin is used, polymerization begins when the monomer and the polymer are mixed together.

  • The material reaches an initial cure stage within minutes; during this time, it hardens and gives off heat, but still can be shaped.

  • The material has reached final set when (1) it can no longer be shaped and (2) the heat has diminished.

  • The tray material is not dimensionally stable for 24 hours.

    • Because of this, the custom tray should be fabricated 24 hours before the patient is scheduled.

Light-Cured Resin Tray Materials

• This premixed, prefabricated tray material is a visible light-cured material that does not contain methyl methacrylate monomer (the hazardous material associated with the acrylic resin material).

• Light-cured resin has very low shrinkage, which provides excellent adaptation of the cast.

  • This tray material is prepared for any impression situation, including dentulous, edentulous, and partially edentulous impressions.

  • With light-cured resins, a curing light acts as the catalyst to bring about polymerization, which allows the material to remain workable until it has been exposed to the light again.

  • Once ex-posed, the resin polymerizes and hardens very quickly.

Vacuum-Formed Thermoplastic Resin

• The vacuum former uses heat and a vacuum to conform a sheet of thermoplastic resin to a diagnostic model. The vacuum former is a versatile machine.

• The major differences in this technique, compared with acrylic resin and light-cured resin applications, are the model preparation and the weight and type of plastic used.

• When constructing an impression tray, you will use a rigid, heavy-gauge plastic that requires a spacer and a handle.

• When constructing a tray for provisional coverage, you will use a lighter gauge plastic that does not require a spacer or a handle.

• When constructing a tray for vital bleaching, you will use a lighter gauge plastic that does not require a spacer or a handle.

• When constructing a mouth guard, you will use a heavier gauge, flexible plastic that does not require a spacer but does require an attachment for the strap.

Dental Waxes

• Dental waxes have a specific purpose in clinical and laboratory procedures.

  • Each wax is derived from a specific by-product.

  • They are derived from natural products, animal by-products, or synthetic products that are made to have certain qualities that cannot be attained from natural sources.

  • Paraffin-derived from mineral

  • Ceresin-derived from mineral

  • Beeswax-derived from animal

  • Candelilla-derived from plant

  • Carnauba-derived from plant

  • Gum dammar-derived from plant

  • Rosin-derived from plant

Classification of Waxes

• Dental waxes are categorized into three general classifications: pattern waxes, processing waxes, and impression waxes.

Pattern Waxes

• Pattern wax is a specific type of wax used in the construction of metal castings and also for the base in the fabrication of dentures.

  • The three types of waxes in this classification are inlay wax, casting wax, and baseplate wax.

Inlay Wax

• Inlay wax is a hard, brittle wax made from paraffin wax, carnauba wax, resin, and beeswax.

  • The dental laboratory technician uses this wax to create a pattern of the indirect restoration on a model.

  • Inlay waxes are classified according to how they flow (hardness), as follows:

    • Type A is a hard wax used for direct wax patterns in the mouth.

    • Type B is a medium inlay wax used for indirect wax patterns on dies.

    • Type C is a soft inlay wax used for indirect waxing techniques in the dental laboratory.

Casting Wax

• Casting wax is like inlay wax, consisting of paraffin, ceresin, beeswax, and resins.

  • Casting waxes are used for single-tooth indirect restorations and fixed bridges and for casting metal portions of a partial denture.

  • This wax is supplied in sheets of various thicknesses.

Baseplate Wax

• Baseplate wax is supplied in sheets and is made from paraffin or ceresin with beeswax and carnauba wax.

  • It is hard and brittle at room temperature.

  • Baseplate wax is used to record the occlusal rims for the initial arch form, for setting denture teeth, and for denture wax-up.

  • The ADA classifies baseplate wax as the following three types:

    • Type I is a softer wax used for impressions in cool climates.

    • Type II is a wax of medium hardness used for impressions in moderate climates.

    • Type III is a harder wax used for impressions in tropical climates.

Processing Wax

• Processing wax is a classification of waxes used either in the clinical or laboratory setting for multiple procedures.

  • The three types of waxes in this classification are boxing wax, utility wax, and sticky wax.

Boxing Wax

• Boxing wax is a soft, pliable wax with a smooth, shiny appearance.

  • It is supplied in long, narrow strips measuring 1 to 1½ inches wide by 12 to 18 inches long.

  • Boxing wax is often used to form a wall or box around a preliminary impression when it is poured, producing a cleaner model without the need to trim as much material.

Utility Wax

• Utility wax is a soft, pliable wax with a slightly tacky consistency.

  • This type of wax is supplied in different forms depending on its use.

  • It can be purchased in strips, sticks, or rope form.

  • Utility wax is made of beeswax, petrolatum, and other soft waxes.

  • Uses of utility wax include extending the borders of an impression tray and covering brackets in orthodontic treatment when they are irritating the cheek or lips.

Sticky Wax

• Sticky wax is a very brittle wax.

  • Its main ingredients are beeswax and resin.

  • This type of wax is supplied in sticks or blocks.

  • Sticky wax is best used in the laboratory in fabrication of castings.

  • When heated, it becomes very tacky and is useful in the casting procedure, creating a wax pattern, or joining acrylic resin together.

Impression Waxes

• Impression waxes are a classification of waxes used to take impressions within the oral cavity.

  • The two types within this classification are corrective impression wax and bite registration wax.

Corrective Impression Wax

• Corrective impression wax is commonly used in the procedure of taking edentulous impressions.

  • This type of wax flows easily at the temperature of the oral cavity, making it useful with other impression materials.

Bite Registration Wax

• Bite registration waxes are soft and very similar to casting waxes.

  • After the wax is softened under warm water, the patient is instructed to bite down, so the wax forms an imprint of the teeth.

  • Bite wafers are another example of bite registration wax.

    • This wax is preformed in a horseshoe shape with a thin sheet of aluminum foil between layers.