Gypsum and Wax Products Chapter 16 DEN 256 Dental Materials

Copyright © 2016 by Saunders, an imprint of Elsevier Inc. All rights reserved. Gypsum and Wax Products 1. Differentiate between negative and positive reproduction. 2. Differentiate among diagnostic cast, working cast, and dies. 3. Describe the chemical and physical nature of gypsum products. 4. Explain the manufacturing process for gypsum products and how this affects their physical characteristics. 5. Compare the following properties and behaviors of gypsum products: strength, dimensional accuracy, solubility, and reproduction of detail. 6. List the American Dental Association–recognized gypsum products and their most appropriate uses. 2 Lesson 16.1

Copyright © 2016 by Saunders, an imprint of Elsevier Inc. All rights reserved. Gypsum and Wax Products 7. Explain initial and final set of gypsum and the factors that affect the setting time, setting expansion, and strength. 8. Explain the procedure for mixing and handling gypsum products to create diagnostic casts. 9. Identify the common components of dental waxes. 10. Compare the properties of waxes. 11. Describe the clinical/laboratory significance of each of the properties of waxes. 12. Discuss the three classifications of waxes. 3 Lesson 16.1

Copyright © 2016 by Saunders, an imprint of Elsevier Inc. All rights reserved. Gypsum and Wax Products 13. Differentiate between direct and indirect waxings and identify which property of dental waxes is most important in their difference. 14. Describe the usual color, form, and use of inlay, casting, baseplate, boxing, utility, and sticky waxes. 15. Prepare model plaster or stone for pouring. 16. Pour the anatomic portion of maxillary and mandibular diagnostic casts. 17. Pour the base portion of maxillary and mandibular diagnostic casts. 18. Trim maxillary and mandibular diagnostic casts. 19. Obtain a bite registration using bite registration or utility wax. 4 Lesson 16.1

Copyright © 2016 by Saunders, an imprint of Elsevier Inc. All rights reserved. Uses and Desirable Qualities of Gypsum Products Gypsum: Mineral that is widely found in nature Ideal for making replicas of the patient’s mouth The replicas are called: Diagnostic casts (also called study models) Working casts (also called working models) Dies 5

Copyright © 2016 by Saunders, an imprint of Elsevier Inc. All rights reserved. Properties and Behaviors of Gypsum Products Chemical properties Mineral gypsum = dihydrate of calcium sulfate Ground to produce a powered hemihydrate Model plaster: Commonly used for diagnostic casts (study models) Dental stone: Used for working casts (master casts) Die stone 6

Copyright © 2016 by Saunders, an imprint of Elsevier Inc. All rights reserved. Properties and Behaviors of Gypsum Products (Cont.) Physical properties Main differences in physical forms dependent on variations in size, shape, and porosity of the powders Strength, hardness, and resistance to abrasion Strength of gypsum products related to the amount of water used to produce the study or working cast 7

Copyright © 2016 by Saunders, an imprint of Elsevier Inc. All rights reserved. Properties and Behaviors of Gypsum Products (Cont.) Physical properties (Cont.) Dimensional accuracy Control setting expansion Reproduction of detail Solubility 8

Copyright © 2016 by Saunders, an imprint of Elsevier Inc. All rights reserved. Classification of Gypsum Products Impression plaster (type I) Rarely used today Model plaster (type II) Frequently used for diagnostic casts Durable but relatively weak material 9

Copyright © 2016 by Saunders, an imprint of Elsevier Inc. All rights reserved. Classification of Gypsum Products (Cont.) Dental stone (type III) Ideal for making full or partial denture models, orthodontic models, and casts, whitening trays, sports guards, partials Dental stone, high-strength/low-expansion (type IV) Often referred to as die stones or densite Used to fabricate crowns and bridges Dental stone, high-strength/high-expansion (type V) Good to use with the newer base metals because of casting shrinkage 10

Copyright © 2016 by Saunders, an imprint of Elsevier Inc. All rights reserved. Manipulation of Gypsum Products Material selection Proportioning (water-to-powder ratio) Mixing: Spatulation Initial setting time and working time Final setting time Control of setting times: Altering the water-to-powder ratio Spatulation Temperature Accelerators and retarders 11

Copyright © 2016 by Saunders, an imprint of Elsevier Inc. All rights reserved. Manipulation of Gypsum Products (Cont.) Fabricating and trimming diagnostic/working casts Diagnostic and working casts have two parts: Anatomic portion Art portion Double-pour method Single-step method Boxing method 12

Copyright © 2016 by Saunders, an imprint of Elsevier Inc. All rights reserved. Manipulation of Gypsum Products (Cont.) Storage Gypsum products can absorb water from the environment Gypsum should be stored in airtight, moisture- proof containers Humidity and close proximity to water sources will adversely affect the powder. 13

Copyright © 2016 by Saunders, an imprint of Elsevier Inc. All rights reserved. Manipulation of Gypsum Products (Cont.) Cleanup Bowls, spatulas, mechanical vibrators, and mixing devices should be cleaned of all traces of gypsum as soon as possible after manipulation 14

Copyright © 2016 by Saunders, an imprint of Elsevier Inc. All rights reserved. Manipulation of Gypsum Products (Cont.) Trimming Cast or study model Model for whitening trays 15

Copyright © 2016 by Saunders, an imprint of Elsevier Inc. All rights reserved. Manipulation of Gypsum Products (Cont.) Infection control and safety issues Separating the impression from the cast Gently ease a lab knife under the impression tray and lift the tray slightly in several areas Care should be taken to not tilt too far in one direction or force the impression and cast apart Broken teeth may result 16

Copyright © 2016 by Saunders, an imprint of Elsevier Inc. All rights reserved. Manipulation of Gypsum Products (Cont.) Metal-plated and epoxy dies and resin-reinforced die stone Type IV and V gypsum products are commonly used die materials Silver or copper plating can create metal-plated dies that are highly resistant to abrasion 17

Copyright © 2016 by Saunders, an imprint of Elsevier Inc. All rights reserved. Manipulation of Gypsum Products (Cont.) Investment materials: Used to form metal castings through the lost wax technique 18

Copyright © 2016 by Saunders, an imprint of Elsevier Inc. All rights reserved. Composition and Properties of Dental Waxes Melting range: Range of temperatures at which each component of the wax will start to soften and then flow Flow: Movement of wax as molecules slip over each other Excess residue Thermal expansion 19

Copyright © 2016 by Saunders, an imprint of Elsevier Inc. All rights reserved. Manipulation of Waxes Softening of wax should be done: Evenly in dry heat With warm hands With a warm water bath By flame Store waxes at or slightly below room temperature to avoid distortion 20

Copyright © 2016 by Saunders, an imprint of Elsevier Inc. All rights reserved. Classification of Waxes Three classifications: Pattern waxes Processing waxes Impression waxes Manufacturers produce these waxes in several forms: Sticks, sheets, blocks, and tins are used 21

Copyright © 2016 by Saunders, an imprint of Elsevier Inc. All rights reserved. Classification of Waxes (Cont.) Pattern waxes Inlay wax – used to prepare patterns for metal casting Casting wax- used to construct the metal framework of partial and complete dentures Baseplate wax-used to make occlusion rims and to hold artificial teeth to baseplates during the fabrication of dentures. -composed of beeswax, paraffin and color matter 22

Copyright © 2016 by Saunders, an imprint of Elsevier Inc. All rights reserved. Classification of Waxes (Cont.) Processing waxes Boxing wax Used to form a box around impressions of the mouth when a cast is made Utility wax Comes in long ropes that are easily manipulated at room temperature May be used with boxing wax to aid in the pouring of an impression Sticky wax Comes in orange sticks that at room temperature are hard and brittle, but when heated under flame become soft and sticky 23

Copyright © 2016 by Saunders, an imprint of Elsevier Inc. All rights reserved. Utility Wax to provide rim locks and otherwise to adapt impression trays for individual impressions is pliable enough at room temperature to be used without heating. normally is issued in stick form and usually is red. 24

Copyright © 2016 by Saunders, an imprint of Elsevier Inc. All rights reserved. Classification of Waxes (Cont.) Impression waxes Corrective impression wax Bite registration wax 25

Copyright © 2016 by Saunders, an imprint of Elsevier Inc. All rights reserved. Why is it necessary to obtain a Bite Registration?Bite Registration Provides the laboratory technician with a reproduction of a patient’s bite. An opposing arch registration for designing the anatomic structures of the fixed prosthetic appliance or device 26 Copyright © 2012, 2009, 2005, 2002, 1999, 1995, 1990, 1985, 1980, 1976 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Copyright © 2016 by Saunders, an imprint of Elsevier Inc. All rights reserved. Bite Registration 27

Copyright © 2016 by Saunders, an imprint of Elsevier Inc. All rights reserved. Flow material over the occlusal and incisal edges evenly, then have patient bite together in a normal occlusion. 28

Copyright © 2016 by Saunders, an imprint of Elsevier Inc. All rights reserved. Bite Registration 29

Copyright © 2016 by Saunders, an imprint of Elsevier Inc. All rights reserved. Questions? 30

Copyright © 2016 by Saunders, an imprint of Elsevier Inc. All rights reserved. Summary Gypsum products are used to produce diagnostic and working models of the patient’s hard and soft tissues The dental assistant and the hygienist may have occasion to use dental waxes in a variety of clinical and laboratory procedures, which makes a basic knowledge and understanding of the material important 31