When pouring an impression the plaster should not be placed?

When pouring an impression, the plaster should not be placed: completed in 30 seconds.

What should be done to an impression before pouring?

Spray the impression with a disinfectant and drain before pouring with stone or plaster. For best results, the model should be poured within 30 minutes after the impression is obtained prevent distortion. Take care to avoid bubbles when pouring the model, since these may affect the fit of the drill guide.

Which of the following steps in pouring a model is performed first?

A method of pouring a dental model. Consists of mixing one large mixture of plaster or stone and pouring up the impression first, and then placing a base material on a tile or counter to invert the impression on a single step.

What is placed on the cast to create room in the tray for the impression material?

A spacer is placed on the cast to create room in the try for the impression material. Baseplate wax, a folded moist paper towel, or a commercial nonstick molding material may be used for this purpose.

What is placed to prevent a tray from seating too deeply?

What is placed to prevent a tray from seating too deeply onto the arch or quadrant? Spacer stops.

Mixing and Pouring Dental Stone

Which of the following is used to prevent a custom impression tray from sitting too deeply when taking the impression?

Which of the following is/are to prevent a custom impression tray from sitting too deeply when taking impressions? place blockout material to fill undercuts in the preliminary cast.

How is the rubber cup placed?

The rubber cup should be filled with the appropriate polishing agent and applied to the tooth surface. Using a low speed, the revolving cup is then lightly applied to the tooth surface with light pressure, ensuring the cup slightly flares and slightly slips into the sulcus.

What are the three types of custom impression trays?

Impression trays are supplied as quadrant trays, which cover half of the arch; section trays, which are suited for the anterior teeth; and full arch trays, which cover the complete arch.

What is the purpose of the holes in the perforated stock impression trays?

Materials commonly used for impression trays are metal, shellac, or resin. They are usually coated with tray adhesive immediately prior to use and may be perforated with 2–4mm diameter holes or made from metallic mesh to improve the adhesion of the impression material to the tray.

Which action occurs if an alginate impression is stored in water?

If an alginate impression is stored in water or in a very wet paper towel, the alginate will absorb additional water and expand. This condition is called imbibition. If an alginate impression remains in the open air, moisture will evaporate from the material, causing it to shrink and distort.

What is impression plaster?

Mainly composed of β-calcium sulphate hemihydrate, impression plaster has a similar composition and setting reaction to the casting material with an increase in certain components to control the initial expansion that is observed with Plaster of Paris.

What are the three types of pouring methods for study casts?

Type 1: Dental plaster, impression. Type 2: Dental plaster, model. Type 3: Dental stone, model.

What are some of the types and common causes of failures encountered with the alginate impression materials?

Why are perforated trays used in alginate impression?

A.

Impression trays are usually perforated so that the alginate will flow through the holes when the tray is seated on the dental arch. These perforations act as a retentive mechanism to keep the set alginate from separating from the tray upon removal.

Where are non perforated trays used?

Description: Dental Impression tray Edentulous Non Perforated is used to take a negative imprint of hard (teeth) and soft tissues in the mouth from which a positive reproduction (cast or model) can be formed. Impression material is of liquid or semi-solid nature when first mixed and placed in the mouth.

What are the functions of an impression tray?

Definition Impression tray that serve to carry the impression material to the mouth & support it in the correct position while it is hardening. This type of the trays can be used for several patients & used for making primary impression.

What is impression tray?

The impression tray is a tool for taking dental impressions of the upper and lower jaw. The impression tray is jaw-shaped and is filled with impression material such as alginate. The tray is then inserted into the patient's mouth. The patient bites into the impression material, leaving the dental impression.

What is impression material?

Impression materials are used to produce a detailed replica of the teeth and the tissues of the oral cavity. From this replica, or impression, a model can be made that is used in the construction of full dentures, partial dentures, crowns, bridges and inlays.

What are the types of impressions?

Which areas or tooth surfaces should be avoided when rubber cup polishing?

Rubber cups, also called prophy cups, are used in the hand-piece. Rubber cups (picture 1) should be only used on enamel and not be used over the cementum area because it may remove a layer of cement tissue it the cervical area.

What position should the patient be placed in when working on the maxillary arch?

Operators may vary placement of patients in a semi-supine position for mandibular procedures and in a supine position for maxillary procedures, or use a chin-up and chin-down method when working on different arches.

Which of the following may be contraindicated for a coronal polishing?

Here are the contraindications for coronal polishing:

Absence of stain. Demineralized spots. Root caries. Gold, composite, acrylic veneers, porcelain restorations.