Master Cast Preparation Flashcards

Questions and Answers

What are the 4 steps of preparing a master cast?

Index the master cast (correct)

Place postpalatal seal on master cast (correct)

Trim the master cast (correct)

Identify anatomic landmarks on master cast (correct)

What are the goals of preparing a master cast?

Making accurate, dense, strong master cast; preserve peripheral border contour of edentulous master impression; facilitate subsequent clinic & lab procedures in CD fabrication.

Type ___________ stone provides master cast with sufficient strength to resist alteration or damage during subsequent steps.

III dental stone

What type of casts are used to fabricate record bases and occlusion rims?

Master Cast Signup and view all the answers

What type of casts are used to reproduce maxillomandibular relationships on an articulator?

Master cast Signup and view all the answers

What type of casts are used to contour trial dentures?

Master cast Signup and view all the answers

List all steps of CD fabrication that require the use of Master cast.

Answer not provided. Signup and view all the answers

What is the ideal vertical height of the base of the master cast?

13~15 mm Signup and view all the answers

If the base of the master cast is too thick (>15mm), what problems does this cause?

Cast may not fit in articulator; cast may not fit in denture flask. Signup and view all the answers

If the land area of the master cast is completely removed, what anatomic features are compromised?

Pterygomaxillary notches; Retromolar pads Signup and view all the answers

What is the ideal dimension of the land area of the master cast?

3 mm wide x 2 mm high Signup and view all the answers

If the land area of the master cast is too THIN, what problems does this cause?

Cast may break; Border contours are lost. Signup and view all the answers

If the land area of the master cast is too SHORT, what problems does this cause?

Cast border contours & dimensions lost; Record base material may not polymerize; Record base difficult to remove from cast. Signup and view all the answers

What step is necessary to preserve the peripheral border contours of the master impression?

Boxing the master impression Signup and view all the answers

What is 'Indexing' a master cast?

Placing a groove/notches in the base of the cast. Signup and view all the answers

________________ is the portion of the cast that extends beyond the impression area laterally.

Land area Signup and view all the answers

Master cast can be largely divided into 2 areas. What are they?

Land area, Impression area Signup and view all the answers

______________ is the portion of the cast that reproduces the surface of oral tissues recorded in master impression.

Impression area Signup and view all the answers

Before trimming the master cast to the right dimension, we should soak it in _________________. For how long?

Clear slurry water; 5-10 minutes Signup and view all the answers

What are the dimensions & criteria for the trimmed master cast?

13-15 mm thick in the thinnest area; Base parallel with residual ridge; Land area: 2 mm high x 3 mm wide; Sides parallel with each other; Sides perpendicular to base of cast; smooth, flat, parallel with benchtop. Signup and view all the answers

What is the purpose of indexing the master cast?

Allows removal of master cast from mounting; accurate replacement of master casts on articulator; facilitates future steps. Signup and view all the answers

Indexing comes before trimming the master cast.

False Signup and view all the answers

Indexing the base of the master cast provides 3D fit between the cast and , allowing easy & __ of the cast.

mounting stone; separation; replacement Signup and view all the answers

What are the dimensions & criteria of the indexing base of cast?

2 mm deep x 3 mm wide; two V-shaped grooves perpendicular to each other; no undercuts & voids Signup and view all the answers

What's the name of the wheel that's used for indexing base of the cast?

#461 blue abrasive wheel on bench lathe Signup and view all the answers

What can you use to shape & refine index grooves afterwards?

#7 green handle knife Signup and view all the answers

Study Notes

Preparing Master Cast

Four steps: trim the master cast, index the master cast, identify anatomic landmarks, and place a postpalatal seal.

Goals of Preparing Master Cast

Create an accurate, dense, and strong master cast.
Preserve the peripheral border contour of the edentulous master impression.
Aid in clinical and laboratory procedures for complete denture (CD) fabrication.

Type of Dental Stone

Type III dental stone (Microstone) offers adequate strength for the master cast while being easy to remove from dentures.

Master Cast Functions

Used for fabricating record bases and occlusion rims.
Essential for reproducing maxillomandibular relationships on an articulator.
Necessary for contouring trial dentures.

Ideal Vertical Height

The ideal base height of the master cast ranges from 13 to 15 mm.

Consequences of Base Thickness

If the base exceeds 15 mm, it may not fit into the articulator or denture flask.

Land Area Importance

Removal of the land area compromises the pterygomaxillary notches and retromolar pads.

Ideal Land Area Dimensions

Should be 3 mm wide and 2 mm high.

Consequences of Land Area Thickness

If too thin, the cast may break and border contours are lost.
If too thick, it hampers denture flask fitting.

Consequences of Land Area Height

A short land area leads to lost cast border contours.
A tall land area can hinder record base polymerization and removal from the cast.

Boxing Purpose

Boxing is necessary to preserve peripheral border contours of the master impression.

Indexing Definition

Indexing involves placing grooves or notches in the base of the cast.

Master Cast Division

The master cast consists of a land area and an impression area.

Impression Area Definition

The impression area reproduces the surface of oral tissues documented in the master impression.

Pre-Trimming Treatment

Before trimming, soak the master cast in clear slurry water for 5-10 minutes.

Trimmed Master Cast Criteria

Thickness should be 13-15 mm in the thinnest area.
The base must be parallel with the residual ridge, with sides smooth, flat, and perpendicular.

Indexing Purpose

Facilitates removal and accurate replacement of master casts on the articulator.
Essential for reproducing maxillomandibular relationships, evaluating trial dentures, and correcting occlusal errors.

Timing of Indexing

Indexing is performed after trimming the master cast.

3D Fit and Function of Indexing

Provides a 3D fit between the cast and the mounting stone, enabling separation and replacement without damage.

Indexing Dimension and Criteria

Should be 2 mm deep by 3 mm wide with two perpendicular V-shaped grooves and no undercuts or voids.

Tools for Indexing

Use a #461 blue abrasive wheel for indexing, with a #7 green handle knife for shaping and refining index grooves.

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Description

Test your knowledge on the steps and goals involved in preparing a master cast. This quiz covers the essential processes such as trimming, indexing, and identifying landmarks. Perfect for dental students aiming to improve their understanding of cast fabrication.