LMP 101

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

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. 

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.

Dental Laboratory Equipment

• Wall-mounted bins 
• Work pans 
• Heat source
• Model trimmer
• Vacuum former
• Vibrator
• Laboratory handpiece
• Sandblaster
• Articulator
• Dental lathe
• Lab instruments

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.

Uses 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 

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

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.
• 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 

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

Pouring Dental Models

• Two parts
  • Anatomic portion
    • Created from the alginate impression
  • Art portion
    • Forms the base of the model

Anatomic and art portions of a dental model.