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

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Presentation on theme: "Laboratory Materials and Procedures Chapter 47 Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved."— Presentation transcript:

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

2 Chapter 47 Lesson 47.1 Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

3 Learning Objectives  Pronounce, define, and spell the Key Terms.  Discuss the safety precautions that should be taken in the dental laboratory.  List the types of equipment found in a dental laboratory and their uses. (Cont’d) (Cont’d) Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

4 Learning Objectives (Cont’d) (Cont’d)  Describe dental models and how they are used in dentistry.  Discuss gypsum products and their role in making dental models.  Mix dental stone.  Pour a set of dental models using the inverted-pour method.  Trim and finish a set of dental models. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

5 Introduction Procedures that take place away from the patient take place in the dental laboratory. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

6 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.

7 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.

8 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.

9 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.

10 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.

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

12 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.

13 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.

14 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.

15 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.

16 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.

17 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.

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

19 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.

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

21 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.

22 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.

23 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.

24 Chapter 47 Lesson 47.2 Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

25 Learning Objectives  Describe the three types of custom impression trays and their use in dentistry.  Construct an acrylic resin custom tray.  Construct a light-cured custom tray.  Construct a vacuum-formed custom tray.  Describe the types of dental waxes and their use in dentistry. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

26 Custom Impression Trays  Criteria  The tray must be sufficiently rigid.  The tray must fit and adapt well to the arch.  The tray must provide accurate adaptation to an edentulous or a partially edentulous arch.  The tray must maintain an even distribution of impression material.  The maxillary tray must cover the teeth, hard palate and extend slightly beyond the gingival margin.  The mandibular tray must cover the teeth and extend beyond the gingival margin. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

27  Undercuts  The first step in cast preparation is to fill all undercuts with wax or other molding material.  Air bubbles in the cast, the shape of the arch and ridge, carious lesions, fractured teeth, and deep interproximal spaces and malposed teeth may cause undercuts.  Outlining the tray  The margins of the cast where the finished tray will be seated are outlined in pencil.  The outline designates the area to be covered by the tray.  The outline extends over the attached gingiva to the mucogingival junction and 2 to 3 mm beyond the last tooth in the quadrant. (Cont’d) Guidelines and Terminology for Creating a Custom Impression Tray Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

28 (Cont’d)  Spacer  Placed on the cast to create room in the tray for the impression material. Baseplate wax, a folded moist paper towel, or a commercial nonstick molding material may be used for this purpose. Baseplate wax, a folded moist paper towel, or a commercial nonstick molding material may be used for this purpose.  To create the spacer, cut a length of baseplate wax, warm it, and place it on the cast over the area of the tray.  A warmed plastic instrument is used to lute the wax to the cast. (Cont’d) Guidelines and Terminology for Creating a Custom Impression Tray Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

29 (Cont’d)  Spacer stops  Triangular or round holes are cut out of the spacer with the use of a laboratory knife or wax spatula.  These cutouts are placed to prevent the tray from seating too deeply onto the arch or quadrant.  Allow for an adequate quantity of impression material around the preparations. The cutouts form bumps on the tissue side of the tray. (The tissue side is the inner surface of the completed tray.) The cutouts form bumps on the tissue side of the tray. (The tissue side is the inner surface of the completed tray.)  An edentulous tray requires a minimum of four stops, one each on the crest of the alveolar ridge in the area of the first or second molar. Additional stops may be placed on the crest of the ridge in the area of each canine.  A tray used to take an impression of prepared natural teeth, as for a crown or bridge, has the stops placed near, but not on, the prepared teeth. (Cont’d ) Guidelines and Terminology for Creating a Custom Impression Tray Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

30 (Cont’d)  Separating medium  The prepared cast, spacer, and immediate surrounding area are painted with a separating medium so that the completed tray can be readily separated from the cast.  Handle  A handle adapted to the tray will allow easier placement in and removal from the patient’s mouth.  Always placed at the anterior of the tray, as near the midline as possible, facing outward and parallel to the occlusal surfaces of the teeth.  The handle is formed from a piece of scrap acrylic that has been cut away from the tray.  The end of the handle and the area where it will be attached to the tray are moistened with tray resin liquid. (Cont’d) Guidelines and Terminology for Creating a Custom Impression Tray Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

31 (Cont’d)  Spacer removal  After the tray has been formed, remove the spacer and clean the tissue side of the tray.  A small, stiff brush, such as a toothbrush, is used to remove most of the wax at this time.  Remove the remainder of the spacer and clean the interior of the tray after it reaches its final set. (Cont’d) Guidelines and Terminology for Creating a Custom Impression Tray Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

32 (Cont’d)  Finishing  Rough areas on the tissue side of the tray do not need to be removed; this surface will be covered with impression material.  Smooth any rough outer edges of the tray so they do not injure the tissues of the patient’s mouth. A laboratory knife can be used to smooth minor rough areas. A laboratory knife can be used to smooth minor rough areas. An acrylic bur in a straight handpiece can be used to remove major rough areas. An acrylic bur in a straight handpiece can be used to remove major rough areas. An alternative is to use the laboratory lathe to smooth the edges. An alternative is to use the laboratory lathe to smooth the edges.  Give the tray a final rinse and disinfect it in accordance with the manufacturer’s instructions. Guidelines and Terminology for Creating a Custom Impression Tray Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

33 Custom Tray Materials  Self-curing acrylic resin  The resin provides a strong and easily adaptable material to create a custom tray.  Disadvantage: The liquid monomer is very volatile and so poses a hazard. (Cont’d) Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

34 Custom Tray Materials (Cont’d)  Material for light-cured resin trays  The premixed, prefabricated light-cured tray material does not contain methylmethacrylate monomer.  The properties of this material provide excellent adaptation of the model.  The material is used for any impression situation: dentulous, edentulous, or partially edentulous. (Cont’d) Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

35 Custom Tray Materials (Cont’d)  Vacuum-formed thermoplastic resin  Uses heat and vacuum to shape a sheet of thermoplastic resin to a diagnostic model  Uses Impression trays Impression trays Making of provisional Making of provisional Vital bleaching trays Vital bleaching trays Mouth guards Mouth guards Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

36 Dental Waxes  Boxing wax  Soft, pliable wax with a smooth, shiny appearance.  Supplied in long narrow strips measuring 1 to 1½ inches wide and 12 to 18 inches long.  Used to form a wall or box around a preliminary impression when pouring. (Cont’d) Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

37 Dental Waxes (Cont’d)  Utility wax  This wax is supplied in various forms, depending on its use.  It is composed of beeswax, petrolatum, and other soft waxes.  Uses Extend the borders of an impression tray Extend the borders of an impression tray Cover brackets in orthodontic treatment Cover brackets in orthodontic treatment(Cont’d) Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

38 Dental Waxes (Cont’d)  Sticky wax  Supplied in sticks or blocks  Main ingredients are beeswax and rosin  Very brittle but becomes very tacky when heated  Useful in the creation of a wax pattern or joining of acrylic resin (Cont’d) Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

39 Dental Waxes (Cont’d)  Inlay casting wax  Hard, brittle wax made from paraffin wax, carnauba wax, resin, and beeswax  Used to create a pattern of the indirect restoration on a model  Classified according to flow: Type A: hard-inlay wax Type A: hard-inlay wax Type B: medium-inlay wax Type B: medium-inlay wax Type C: soft-inlay wax Type C: soft-inlay wax(Cont’d) Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

40 Dental Waxes (Cont’d)  Casting wax  Made up of paraffin, ceresin, beeswax, and resins  Supplied in sheets of various thicknesses  Used for single-tooth indirect restorations, fixed bridges, and casting of metal portions of a partial denture (Cont’d) Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

41 Dental Waxes (Cont’d)  Baseplate wax  Made of paraffin or ceresin with beeswax and carnauba wax  Hard and brittle at room temperature  Supplied in sheets  Three types Type I: softer wax used for denture construction Type I: softer wax used for denture construction Type II: medium-hardness wax used in moderate climates Type II: medium-hardness wax used in moderate climates Type III: harder wax for use in tropical climates Type III: harder wax for use in tropical climates(Cont’d) Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

42 Dental Waxes (Cont’d)  Bite-registration waxes  These waxes are soft and very similar to casting waxes.  Bite-registration wax softens under warm water.  The patient is instructed to bite down, leaving an imprint of the teeth in the wax. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.


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