Dental Models and Laboratory Materials Flashcards

Flashcards for 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.

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.

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

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.

Dental Lathe

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

• 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

• 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.

• When mixing a gypsum powder with water, the hemihydrate crystals dissolve in the water to form

• clusters known as the nuclei of crystallization.

• As more intermeshing of crystals occurs,

• the strength, rigidity, and hardness of the final product is increased.

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.

Vibrator

Used to remove air from the mix of gypsum products.

Model Plaster

Commonly referred to as plaster of Paris.

Dental Stone

Used as a working model for making dentures.

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 Models/ Study Casts

A reproduction of the teeth and surrounding soft tissues of the patient's maxillary and mandibular arches

Gypsum

A mineral mined from the earth and In its unrefined state, gypsum is the dihydrate form of calcium sulfate, consisting of two parts water to one part calcium sulfate.

Model plaster

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

Dental Stone

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

Die Stone

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

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

Criteria for Creating Custom Impression Trays

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

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

Spacer stops

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

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

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.

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).

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.

Pattern Waxes

A specific type of wax used in the construction of metal castings and also for the base in the fabrication of dentures.

Inlay Wax

hard, brittle

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

Casting Wax

used for single-tooth indirect restorations and fixed bridges and for casting metal portions of a partial denture

Baseplate Wax

supplied in sheets and is made from paraffin or ceresin with beeswax and carnauba wax.It is hard and brittle at room temperature.

Processing Wax

used either in the clinical or laboratory setting for multiple procedures

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.

Utility Wax

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.

Sticky wax

a very brittle wax.Its main ingredients are beeswax and resin.This type of wax is supplied in sticks or blocks.

Impression Waxes

used to take impressions within the oral cavity

Corrective Impression Wax

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.

Impression Plaster I

• 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

• 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

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.

• The crystals in plaster are

• irregularly shaped and very porous

• model plaster requires the

• greatest quantity of water for mixing, produces weakest form of a study model.

Dental Stone (Type III)

• 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

• The crystals in dental stone are more uniform in shape and less porous

• Study model is stronger and denser

Die Stone (Type IV)

Water to powder ratio 19-24ml

• 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)

19-24

• strongest stone, with the least amount of expansion.

  • The crystals  are smooth and very dense and require the least amount of water 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.

• The anatomic portion create from

Alginate impression

• anatomic portion includes

• teeth, the mucosa, and the frenum attachments.

• art portion Froms 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

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

• the teeth, oral mucosa, and muscle attachments.

• Anatomic portion Make up

• 2/3 overall trimmed cast

• art portion make up

• 1/3 of the overall trimmed cast.

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

Double pour

Box and pour

Inverted pour

• 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(most common)

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.

• Models must have a professional appearance when used for

• a case presentation or as part of the patient's permanent record.

• Models must have a professional appearance it Is accomplished by

• trimming the models to a geometric standard.

Wax bite registrations

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

• 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  solution is a commercial model gloss spray

• 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

• They are created in the lab within the office, or lab tech. can prepare these before the patient returns for their appointment.

Criteria for Creating Custom Impression Trays

• Tray must be sufficiently rigid to hold and support materials during(placement/removal)

• Tray must fit and adapt well to the arch and maintain patient comfort without impinging 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.

• fill all undercuts with wax or other molding material.

• 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.

• place the spacer on the cast to create room in the tray for the impression material.

• Spacer stops: prevent the tray from seating too deeply onto the arch or quadrant.

• 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.

    Spacer removal:

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

  • Finishing:

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

Acrylic Resin Tray Materials

Acrylic Resin Tray Materials

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

Acrylic Resin Tray Materials

• The major disadvantage of this material involves the

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

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.

Important

Light-Cured Resin Tray Materials

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

Vacuum-Formed Thermoplastic Resin

• 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 are categorized into three general classifications:

• pattern waxes,

• processing waxes

• impression waxes.

Pattern Waxes

• used in the construction of metal castings and the base in the fabrication of dentures.

• The three types of patterns waxes in this classification are

• inlay wax, casting wax, and baseplate wax.

Inlay Wax

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

Casting Wax

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

Baseplate Wax

Baseplate Wax

• Baseplate wax is supplied in sheets

  • It is hard and brittle at room temperature.

  • 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

• used in the clinical or laboratory setting for multiple procedures.

• The three types of processing waxes in this classification are

• boxing wax, utility wax, and sticky wax.