Mr. Caputo Unit #1 Lesson #10 Diagnostic Cast Mr. Caputo Unit #1 Lesson #10

Today’s Class Driving Question: How are diagnostic cast utilized in the dental office? Learning Intentions: We will be able to describe various methods of constructing custom trays and demonstrate creating a light-cured custom tray. Anchor: What personal protective equipment should be worn by the dental assistant when pouring a stone cast?

Diagnostic Cast Models Duplicate patient’ s teeth and mouth structures for diagnostic purposes Made from quality dental impressions Used as models for further fabricating dental prostheses Used as education tool From initial casts dental prostheses are made that fit patient’s jaw structure and resemble other teeth

Gypsum Materials Used in dentistry to create diagnostic cast models of maxillary or mandibular arch Most common are plaster, stone, and high-strength stone Composed primarily of calcium sulfate dihydrate Supplied as powder During setting process gypsum gives off heat in an exothermic reaction

Strengths of Gypsum Products Plaster of Paris Dental stone Die stone To learn more about gypsum products and other dental materials, click here or go to http://www.free-ed.net/sweethaven/MedTech/Dental/ DentMat/default.asp

Plaster of Paris Used for pouring cast models for preliminary study, diagnostic reasons, to attach casts onto articulators, and for general use in the dental lab when strength is not important Because of porous and irregular particles, plaster requires more water when being mixed Initial setting time is from 5 to 15 minutes and is completely set within 45 minutes Removal of cast from mold too soon can result in fractures to the cast

Dental Model

Stone Available in yellow or buff color Requires less water when mixing, and sets more slowly than plaster When set, stone is harder, denser, and has a higher crushing strength than plaster Harder stone casts provide excellent master casts for fabrication of dentures, bleach trays, athletic mouth guards, and temporary crown splints

Stone Spatulation is completed in 30 to 60 seconds on a vibrator Initial setting time for artificial stone is usually 8 to 15 minutes and final setting time is approximately 45 minutes

Die Stone Strongest gypsum product Used to create working casts for fixed prostheses and partial dentures Most often poured by the dental laboratory technician Mix must not be too thick or too thin so that it flows into the dentition easily and yet is thick enough to maintain strength

Preparing to Pour a Model

Steps to Pouring a Dental Model Use a clean, dry mixing bowl and spatula Measure volume of water and weigh powder Always add powder to water and not water to powder Spatulate thoroughly by hand, incorporating all the powder evenly throughout the mix until creamy Avoid whipping the mix

Steps to Pouring a Dental Model Vacuum mixing with a power mixer-investor helps eliminate incorporation of air into the mix Hold bowl against a vibrator for a few minutes to cause trapped air to rise to the surface Never add water to a mix that is too thick

Pouring of Models

Filling the Impression

Parts of a Cast Model Click here for a question to consider Anatomic portion: includes teeth and oral structures the base should make up two-thirds of the model Art portion: makes up one-third Click here for a question to consider

Question to Consider What is the difference between the maxillary and mandibular trimmed models?

Setting the Anatomic and Art Portions

Anatomic and Art Portion of a Dental Cast Model

Homework #4 Explain how you would train a dental worker in infection control.