Laboratory Materials and Procedures Chapter 47 Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Uses of the Dental Laboratory  Making models from preliminary impressions  Trimming and finishing diagnostic models  Preparing custom trays  Polishing  Provisional coverage  Partial or full dentures  Indirect restorations Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Laboratory Rules  Eating, drinking, and smoking are prohibited.  Keep all cosmetics out of this area.  Wear personal protective equipment when working in the laboratory.  Keep hair back.  Report all accidents to the dentist immediately.  Follow the manufacturer’s instructions for the operation of equipment.  Clean the work area before and after every procedure. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Safety in the Lab  Physical safety  Know the location of the fire extinguisher and fire- escape routes.  Chemical safety  Take care in the handling of corrosive, toxic, and carcinogenic substances.  Biohazards  Items brought into the laboratory can harbor blood and saliva that may be infective. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Dental Laboratory Equipment  Wall-mounted bins  Work pans  Heat source  Model trimmer  Vacuum former  Vibrator  Laboratory handpiece  Sandblaster  Articulator  Dental lathe  Lab instruments Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Dental Models Dental models are three-dimensional reproductions of the teeth and the surrounding soft tissue of a patient’s maxillary and mandibular arches. They are also referred to as study casts. Dental models are three-dimensional reproductions of the teeth and the surrounding soft tissue of a patient’s maxillary and mandibular arches. They are also referred to as study casts. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Fig Dental models. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Use of Dental Models  Diagnosis for a fixed or removable prosthetic  Diagnosis for orthodontic treatment  Visual presentation of dental treatment  In the making of custom trays  In the making of orthodontic appliances  In the making of provisional coverage  In the making of mouth guards Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Gypsum Products  Used extensively in dentistry to make dental models  Chemical properties of gypsum  A mineral that is mined from the earth  In its unrefined state, the dihydrate form of calcium sulfate  Converted into a powdered hemihydrate Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Physical Forms of Gypsum  Model plaster  Commonly called plaster of Paris.  Used primarily for pouring preliminary impressions and the making of diagnostic models  Dental stone  For use as a working model when a more durable diagnostic cast is required.  Examples include the making of custom trays and orthodontic appliances. (Cont’d) Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Physical Forms of Gypsum (Cont’d)  High-strength stone  Also known as densite or improved dental stone  Ideal, because of its strength, hardness, and dimensional accuracy, for the creation of the dies used in the production of crowns, bridges, and indirect restorations Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Recommended Powder/Water Ratios for Gypsum Products Model plaster (100 g) to 45 to 50 mL of water Dental stone (100 g) to 30 to 32 mL of water High-strength stone (100 g) to 19 to 24 mL of water Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Pouring Dental Models  Two parts  Anatomic portion Created from the alginate impression Created from the alginate impression  Art portion Forms the base of the model Forms the base of the model Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Fig Anatomic and art portions of a dental model. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Different Pouring Methods  Double-pour method  The anatomic portion of the model is poured first; then a second mix of plaster or stone is used to prepare the art portion.  Box-and-pour method  The impression is surrounded with a “box” made of wax and poured as one unit.  Inverted-pour method  One large batch of plaster or stone is mixed and both portions of the model are poured in a single step. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Fig Examples of pouring methods. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Trimming and Finishing of Dental Models  Prepare the model  Soak it in water for 5 minutes.  Trimming the maxillary model  Trim the base.  Trim the posterior area.  Trim the sides.  Trim the heel cuts.  Trim the angled portion from canine to canine. (Cont’d) Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Trimming and Finishing of Dental Models (Cont’d)  Trimming the mandibular model  Trim the posterior portion of the mandibular model until it is even with the maxillary model.  Trim the base.  Trim the lateral cuts to match the maxillary lateral cuts.  Trim the back and heel cuts.  Trim from canine to canine in a rounded form. (Cont’d) Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Trimming and Finishing of Dental Models (Cont’d)  Finishing the model  Mix a slurry of gypsum and fill in any voids.  Polishing a plaster model  Soak the model in a soapy solution for 24 hours.  Dry the model and then polish it with a soft cloth. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.