Diagnostic Casts And Related Procedures Notes

Dental Cast Introduction

The dental cast represents a denture foundation in the absence of the patient. It is used for diagnosis and treatment planning. A denture is fabricated on a cast made from an impression of a denture foundation. It is a positive replica of the denture foundation and a negative replica of the impression. It should be made properly for ease of handling and manipulation of material over it. This chapter deals with types of casts, methods of pouring casts, their dimensions, and characteristics.

Dental Cast Definition

Cast:

A life-size likeness of some desired form.

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Dental Cast:

A replica of the tooth surfaces, residual ridge areas, and/or other parts of the dental arch and/or facial structures used to fabricate a dental restoration or prosthesis.

Types Of Dental Cast

Diagnostic Cast:

It is made to diagnose the present condition of diseases or oral conditions. Sometimes mock surgical procedures are performed on diagnostic casts to estimate outcomes. It is made up of dental plaster (type II gypsum).

Primary Cast:

It is made from primary impression. The custom tray is fabricated on the primary cast. It is poured into dental plaster (type II gypsum). It is made by the inversion method.

Master Cast/Final Cast:

This cast is obtained by pouring the final/master impression. Usually prosthesis is fabricated on this cast. It is more accurate than the primary cast and has more fine details. It is made with dental stone (type III gypsum). It is made by the beading-boxing method.

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Ideal Requirements Of The Cast

• The cast should be neat, clean, and free of voids and blebs.
• The base should be of 15 mm in thickness.
• Land area should be of 2–3 mm in height and width and slopped at 45° angulation.

• The Denture foundation area should not be altered or represented as recorded in the impression.
• The Denture foundation area should be parallel to the base of the cast.
• The land area should follow the depth of the vestibule.
• The cast should be labeled with the patient’s name and OPD number.

Parts Of Dental Cast

A dental cast has two parts namely:

1. Anatomic portion
2. Art portion.

Anatomic Portion:

This part of the dental cast is made by pouring the impression of oral tissue. It represents anatomical landmarks or denture foundation areas.

Art Portion:

This portion is added to an anatomic portion of the cast to provide better strength and handling characteristics. It includes a base of the cast, the heel of the cast, and the land area of the cast. The base and land area of the cast are important as they impart strength to the cast, preserve the depth and width of the sulcus, and protect anatomical landmarks/areas of the cast.

The base of the cast should have a 15 mm thickness at the deepest part of the cast. The land area should have 3–4 mm in height from the sulcus and 3–4 mm in width. The land area should be sloped outward at 45° angulation.

Refractory Cast:

This cast is made from type IV gypsum. The material has characteristics of high strength and high expansion. This cast is used to fabricate wax patterns of cast partial framework. This cast can withstand high temperatures.