Dental Assisting Chapter 22

Paste system

the material is supplied in tubes and involves the use of a spatula and paper pad. The catalyst is picked up and spatulated into the base until the material is uniform in appearance. The material is then gathered onto the spatula and loaded into the tray

Fast set alginate

working time of 1 1/4 minutes and a setting time of 1-2 minutes

Automix system

A mixing technique available for use with impression materials, Automix systems are designed by the manufacturers to complete the mixing process for the procedure. The unique automix system device provides a homogeneous mix with the appropriate amount of material without waste.

Addition silicone

A paste material supplied as a two-paste system, as a putty material, or in cartridges. This material has an acceptable odor and taste. The stiffness and stability are excellent. Easy to mix, short mixing time (30-45 seconds), average set time 6-8 minutes

Alginate

A salt of alginic acid, sodium alginate, which, when mixed with water in accurate proportions, forms an irreversible hydrocolloid gel used for making impressions.

Diagnostic cast

A stone or plaster model of dental structures for the purpose of study and treatment planning

Stone

Abrading instrument or tool

Registration

Act of completing forms by providing personal information

Sol

Alginate goes through a solution phase during which the material is in a liquid or semi liquid form

Bite registration paste

Bite registration materials have gained popularity in taking a bite registration because of material; is fast setting, convenient to use, supplied as a two paste system or cartridges, can be directly applied to the arch or to gauze tray, paste has no odor or taste, no resistance to biting forces.

Elastic material

Can be deformed and returned to their natural appearance. This type includes alginate, elastomers, and agar

Condensation silicone

Compound of organic structural character in which all or some of the positions that could be occupied by carbon atoms are occupied by silicon, supplied as a paste and liquid, acceptable odor and taste, stiffness and stability are average, easy to mix 30-60 seconds set time 6-10 minutes

Plaster

Dental plaster of Paris, plaster is used for pouring preliminary impressions and for making diagnostic models.

Viscosity

Final impression material is supplied in three forms or viscosities. Is the ability of the material to flow. 3 forms;

Polysulfide

Final impression material that has been used in dentistry for many years; also referred to as rubber base, polysulfide is supplied as two-paste system, has a strong odor & taste - the base and the catalyst. Harder to mix, longer mixing time, longer set time 10-20 minutes

Dental stone

Form of gypsum, is stronger than model plaster and is commonly used when a more durable diagnostic cast is required, example: when used as a working model to make a retainer, a custom tray, or castaing by the laboratory technician

Centric

Having an object centered, such as maxillary teeth centered over mandibular teeth in correct relation

Imbibition

If the alginate absorbs too much water then it can cause it to expand

Polyether

Impression material that provides better mechanical properties than polysulfide and less dimensional change than silicone. A paste material supplied in tubes or cartridges. Easy to mix, short mixing time (30-45 seconds) and fast setting time (6-7 minutes)

Mechanical property

Indicates the flexibility of material. Two types of material are inelastic and elastic.

Setting property

Irreversible material indicates that a chemical reaction has occurred and that the material cannot go back to its original state. This type includes alginate elastomeric impression materials, ZOE impression paste, and impression plaster. Reversible material can be altered by temperature and includes agar and impression compounds

Model plaster

Is a derivative of plaster, is used when strength is not essential and dimensional accuracy is not critical. Model plaster is easy to trim and is excellent for diagnostic casts because of its clean appearance

Water coolant tray

Is a metal tray that is used with reversible hydrocolloid impression material. Used for final impression

Gauze tray

Is a thin mesh like material that allows the patient to bite normally. Used for bite registration

Custom tray

Is customized to fit a patient's mouth and made from light cured resin, acrylic resin, or thermoplastic resin. Used for final impression

Triple tray

Is designed to eliminate steps by taking the final impression and bite registration at the same time. Used for final impression and bite registration

Plastic sooth tray

Is supplied in standard sizes. Requires an adhesive to be applied to hold the impression material securely in the tray. Used for final impression

Perforated tray

Is the performed tray made from metal or hard plastic and is supplied in standard sizes for children through adult. Allows the impression material to form a mechanical lock with the tray. Used for preliminary impressions

Preliminary impressions

Is used for making diagnostics models, custom trays, provisional coverage, dental orthodontic appliances, and pretreatment and post treatment records.

Model trimmer

Machine used to trim stone or plaster models

Irreversible hydrocolloid

Material of choice when taking preliminary impressions, hydro means water, and colloid means a gelatinous substance.

Elastomeric impression materials

Materials have an elastic or rubber like quality after setting.

Water to powder ratios

Model plaster: 45-50 ml of water to 100 g powder Dental stone: 30-32 ml of water to 100 g powder High strength stone: 19-24 ml of water to 100 g powder

Dimensional change

Most alginate impression materials must be poured up within 1 hour of taking the impression. A requirement dictated by the environment. Because much of the material is derived from water, a slight change in its environment can distort the impression and cause this change

Impression

Negative reproduction of an object from which a positive reproduction may be made

Taking Alginate impressions

Preliminary impressions are used to create a negative reproduction of the teeth and their surrounding tissue and structures. When an impression is poured up in stone or plaster to make a model, it is then creating a positive reproduction of the teeth and their surroundings

Putty impression material

Provides the benefits of true putty, including a dense consistency of insertion force than observed with heavy-bodied materials. Because the material is kneaded in the palms, the material is already warm when it is seated in the mouth

Cast

Referred to as a model

Occlusal bite registration

Reproduces the occlusal relationship of the maxillary and mandibular teeth when occluded. When the casts of the upper and lower jaws are mounted on the articulator, this bite registration is used to establish te proper centric relationship.

Final impressions

Shows accurate detail of the tissue and tooth structures for the laboratory technician to make a cast restoration, inlay, onlay, veneer, crown, or bridge

Gel

Solid phase for alginate during which the material becomes semi solid.

Table top or wall mounted mixing unit

This unit saves time and mechanically mixes the material and expresses it into the tray

Extrude

To push or force out

Wax bite registration

Used to show the occlusal relationship of the maxillary and mandibular teeth

Syneresis

When the alginate impression remains in open air then moisture will evaporate from the material causing it to shrink and distort.

Normal set alginate

Working time of 2 minutes and a setting time of up to 4 1/2 minutes after mixing

Impression materials

are selected because of their unique qualities that allow the dentist to obtain the most accurate reproduction. An impression material is classified according to specific properties; mechanical and setting

Base and catalyst

are self curing

Full arch trays

cover the entire arch

Quadrant tray

covers half of an arch

Section tray

covers the anterior portion of the arch

Inelastic material

is rigid and will fracture when deformed. This type included impression compounds, impression plaster, and zinc oxide-eugenol (ZOE) impression paste

Regular body final impression material

is slightly thicker than the light body form. This material is used as a tray material but has the ability to flow easily, thus requiring improved control from the tray

Light body final impression material

is the easiest flowing material of all three forms. This material is expressed from a syringe around the tooth and into the sulcus of the prepared tooth or teeth, which provides the detail of the margin that was created by the dentist

Heavy body final impression material

is the thickest of the three forms. This material is used as a tray material and has the ability to force the light bodied material into close contact with the prepared tooth and surrounding tissue to ensure a more accurate impression.