Impression Making for Complete Denture Flashcards

A set of 100 question-and-answer flashcards covering complete denture impression techniques, objectives, materials, and tray fabrication based on the provided lecture transcript.

What is the general definition of an impression in dentistry?

A negative likeness or copy in reverse of the surface of an object.

What is a dental impression?

An imprint or negative likeness of the teeth and/or edentulous area and adjacent tissue.

How is a complete denture impression defined?

A negative registration of the entire denture bearing, stabilizing, and border seal areas of either the maxilla or the mandible present in the edentulous mouth.

List the five objectives of complete denture impression making.

1-Preservation of the residual alveolar ridge and soft tissue. 2- Support for denture. 3- Stability. 4-Support for esthetic. 5- Retention.

What effect does pressure in the impression technique have on tissues?

It results in soft tissue damage and bone resorption.

Define support in the context of a prosthesis.

The quality of prosthesis to resist the forces which try to dislodge the denture in a tissue-ward direction.

Upon what three factors does support depend?

Denture base, Bone, and soft tissue.

What provides the best support for a denture?

Compact bone covered with fibrous connective tissue.

Why does maximum coverage provide greater support?

It distributes applied forces over as wide an area as possible.

Define stability in complete denture prosthetics.

The resistance to functional horizontal or rotational movements which try to dislodge the denture.

What factors cause a decrease in stability?

The loss of vertical height of the residual ridges or an increase in flabby, movable tissue.

Upon what two factors does stability depend?

Denture base and Bone.

How should border thickness be determined for esthetics?

It should be varied with the needs of each patient in accordance with the extent of residual ridge loss.

What is the goal of filling the vestibular fornix?

To restore facial contour without overfilling.

Define retention.

The resistance to the forces which try to dislodge the denture in a direction opposite to the path of insertion.

Upon what two factors does retention depend?

Denture base and soft tissue.

Contrast retention and stability in terms of relation to tissues.

Retention is the constant relation of the denture base to underlying soft tissues, while stability is the relation of the denture base to underlying bone.

When must retention hold the denture in position?

When it is seated at rest.

What must stability resist specifically?

Displacement by rocking when a force is applied to teeth over a limited area.

List the factors that may affect retention.

Atmospheric pressure, adhesion, cohesion, mechanical locks, muscle control, and patient tolerance.

What happens if an impression records the depth of the sulcus but not its width?

The resulting denture will lack adequate retention.

What is a primary impression?

An impression made for the purpose of diagnosis, treatment planning, and construction of a special tray.

What type of tray is used to obtain primary impressions?

A stock tray.

What landmark must be included in a maxillary primary impression?

The hamular notches, fovea palatina, frenum attachments, palate, and the entire labial buccal vestibules.

What landmark must be included in a mandibular primary impression?

The retromolar pad, buccal shelf areas, external oblique ridges, frenum attachments, sublingual space, retromylohyoid space, and the entire labial and buccal vestibules.

List 3 materials used for making primary impressions.

1- Impression compound. 2- Alginate impression material. 3- Putty body silicon rubber base.

What are the two types of impressions made for a complete denture patient?

1- Primary impression. 2- Final or Secondary impression.

Define an impression tray.

A device used to carry, confine, and control the impression material while making an impression.

What are the main parts of an impression tray?

1- Body (consisting of Floor and Flange) and 2- Handle.

What is the name of the palatal portion found in an upper tray?

Vault.

What part is found in a lower tray but not an upper tray?

Lingual flange.

Describe the location and shape of the tray handle.

It is an extension from the union of the floor and labial flange in the midline; it is (L) in shape.

Why is the tray handle (L) shaped?

So that it will not interfere with the lip during the impression procedure.

What are the two general types of trays?

1- Stock tray and 2- Special tray (individual or custom tray).

What is a stock tray?

An impression tray used to carry material to the mouth and support it in the correct position while hardening, typically used for primary impressions.

What materials are commonly used to make stock trays?

Aluminum, Tin, Brass, or plastic.

List the two types of stock trays based on the presence of teeth.

1- Stock tray for dentulous patient and 2- Stock tray for edentulous patient.

How do the flanges of edentulous stock trays differ from dentulous ones?

Edentulous trays have short flanges, while dentulous trays have long flanges.

How do the floors of edentulous stock trays differ from dentulous ones?

Edentulous trays have an oval and narrow floor, while dentulous trays have a flat and wide floor.

When is a perforated stock tray used?

With alginate impression material for mechanical retention.

When is a non-perforated stock tray used?

With sticky impression material like impression compound.

How much space should a stock tray provide for impression material in all directions?

$$4-5\,mm$$

How is a primary cast (study model) produced?

By pouring the primary impression with plaster.

At what temperature should water be to separate a plaster cast from a compound impression?

$$55-60^{\circ}C$$

Why should very hot water be avoided when separating a cast from impression compound?

The impression compound will become sticky and difficult to remove.

What is a secondary (final) impression?

An impression made for the purpose of fabrication of a prosthesis, made with an individual tray.

What material is used to pour the final impression to produce the master cast?

Dental stone.

List 4 materials used for final impressions.

1- Zinc Oxide Eugenol. 2- Alginate. 3- Elastomers (Rubber base). 4- Impression plaster.

What are the two common names for the technique that records soft tissues in a functional position?

Closed mouth technique or Pressure technique.

What are the two techniques for recording soft tissues in a rest position?

A. Nonpressure technique (Passive or Mucostatic technique) and B. Selective pressure technique.

Define a special tray (individual or custom tray).

A custom made device prepared for a particular patient used to confine and control impression material for the final impression.

Why is a special tray constructed on a primary cast rather than using a stock tray?

Because edentulous ridges variations in shape and size mean a stock tray can only fit in an arbitrary manner.

List 6 advantages of a special tray.

1- Economy in material. 2- More accurate impression. 3- Even material thickness. 4- Easier/quicker than modifying stock trays. 5- Better adaptation to vestibules. 6- Less bulky/more comfortable.

What materials can be used for special tray construction?

1- Cold and heat cured acrylic. 2- Light cured resin. 3- Impression compound (higher fusing).

What are the two types of special trays?

1- Spaced special tray (with or without stoppers) and 2- Closed fit special tray.

In the fabrication of a special tray, why are borders grooved on the cast?

To act as a guide to trim the tray later.

How thick should the wax spacer be for a spaced special tray?

About $2\,mm$

Which area of the maxillary cast is not covered with the wax spacer?

The posterior palatal seal area.

What is a stopper in a special tray?

The part of the tray that extends into a cut out of the spacer ($2-4\,mm$) to touch the ridge and stabilize the tray.

How many stoppers are usually placed, and where?

4 stoppers: 2 on the canine eminence and 2 in the molar region on either side.

When is the wax spacer removed in the spaced special tray technique?

It is left inside the tray until it reaches the mouth for the border molding procedure.

What are the three stages of mixing monomer and polymer in the dough technique?

Sandy stage, stringy stage, and dough stage.

What is the required thickness for the acrylic sheet in the dough technique?

$$2\,mm$$

How is the acrylic sheet adapted over the cast to prevent wrinkles?

From the center to the periphery.

Describe the sprinkle-on technique for special tray construction.

Monomer and polymer are applied in alternate layers until relative thickness is achieved.

What is an advantage of the sprinkle-on technique?

Ease of use and minimal wastage of material.

When using light cured resin for a special tray, what is done with the models to remove wax?

They are boiled free of wax.

Why is a light cured tray inverted and returned to the curing box?

To cure the inside of the handle area, which can be quite thick.

What criteria must a special tray meet regarding rigidity?

The tray should be rigid and of sufficient even thickness that it will not fracture.

How far under-extended should special tray borders be?

$$2\,mm$$

Why should the posterior limits of the upper special tray be slightly over-extended?

To ensure inclusion of the posterior detail for the development of the post-dam area.

What is the definition of beading?

A procedure done to preserve the width and height of the sulcus in a cast.

What is the definition of boxing?

The enclosing of an impression with beading wax to produce the desired size and form of the base of the cast.

Why can boxing typically not be used on hydrocolloid (alginate) impressions?

The boxing wax will not adhere to the material and alginate can be easily distorted.

What is the minimum thickness for the base of a cast?

$$11-15\,mm$$

Where should beading wax be attached to the impression?

Approximately $2-3\,mm$ below the border.

What is the width of the boxing wax sheet?

About $9-15\,mm$

What is the purpose of base plate wax in boxing a mandibular impression?

To fill the tongue space.

Where is base plate wax sealed in a mandibular boxing procedure?

Just below the lingual border of the impression.

List 6 common faults in impression making.

1-Poor tray/material selection. 2-Insufficient material. 3-Excessive material. 4-Failure to press tray to position. 5-Incorrect tray position. 6-Obstruction by tissues.

What happens if the tray is not pressed completely to position?

It results in insufficient seating pressure.

What is used to shape the acrylic material in the dough technique?

A plastic roll or glass slabs.

What is applied to the cast before acrylic in both the dough and sprinkle-on techniques?

A separating medium.

In the light cured resin method, what bur is used to trim the periphery?

A carbide bur.

What tool is used to smooth the light cured tray after trimming?

A silicone wheel or point.

What is the positive reproduction of oral tissues produced from a primary impression?

The primary cast (study model).

What is the positive reproduction produced from the final impression?

The master cast.

What material is used to bead the impression before boxing?

Beading wax.

How is the beaded wax sealed to the impression?

With a wax knife.

Which material is used for the saturation method in a rubber bowl when making a study cast?

Plaster mixed with water.

What does 'vault' refer to in tray anatomy?

The palatal portion of an upper tray.

What is the primary factor in obtaining a good working impression after special tray construction?

Proper extension and adaptation on the residual ridge.

Name a specific brand of polysulfide impression material mentioned in the text.

Permlastic (Kerr).

What consistency is mentioned for Permadyne polyether material?

High Consistency.

Identify the type of silicone impression material shown in figure 3-18.

C-Silicon (Zetaplus).

What causes bone resorption in terms of impression technique?

Pressure in the technique is reflected as pressure in the denture base.

What characterizes a closed fit special tray?

A tray that is constructed to fit the primary cast without the use of a spacer.

Why is a special tray less bulky than a stock tray?

It is custom-made for the patient's individual ridge for comfort.

What special precaution is taken in light cured resin tray fabrication regarding frenum attachments?

Taking care to relieve the frenum attachments during trimming and smoothing.

What specific material is 'Hiflex' associated with in the text?

Modelling Wax.