Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Chapter 47 Laboratory Materials and Procedures Copyright 2003, Elsevier Science (USA). All rights reserved. No part of this product may be reproduced or transmitted in any form or by any means, electronic or mechanical, including input into or storage in any information system, without permission in writing from the publisher. PowerPoint® presentation slides may be displayed and may be reproduced in print form for instructional purposes only, provided a proper copyright notice appears on the last page of each print-out. Produced in the United States of America ISBN 0-7216-9770-4 Copyright 2003, Elsevier Science (USA). All rights reserved. Dental Models Three-dimensional reproductions of the teeth and the surrounding soft tissue of a patient’s maxillary and mandibular arches. Also referred to as study casts. Copyright 2003, Elsevier Science (USA). All rights reserved. Use of Dental Models Diagnosis for a fixed or removable prosthetic. Diagnosis of orthodontic treatment. Visual presentation of dental treatment. Making of custom trays. Making of orthodontic appliances. Making of provisional coverage. Making of mouth guards. Copyright 2003, Elsevier Science (USA). All rights reserved. Dental laboratory materials Several materials Will study • Gypsum materials • Dental waxes Copyright 2003, Elsevier Science (USA). All rights reserved. Gypsum Products Used extensively in dentistry to make dental models. Chemical properties • A mineral that is mined from the earth. • In its unrefined state, gypsum is the dihydrate form of calcium sulfate. • Converted into a powdered hemihydrate. Copyright 2003, Elsevier Science (USA). All rights reserved. Classification Gypsum product Impression plaster (type 1) Plaster (type 2) High strength plaster Stone (type 3) High-strength stone( type 4)-Die stone Copyright 2003, Elsevier Science (USA). All rights reserved. Physical Forms of Gypsum Model plaster • Commonly called plaster of Paris, is used primarily for pouring preliminary impressions and the making of diagnostic models. Copyright 2003, Elsevier Science (USA). All rights reserved. Physical Forms of Gypsum-cont’d Dental stone • For use as a working model when a more durable diagnostic cast is required. Examples are in the making of custom trays and orthodontic appliances. Model made of dental stone Copyright 2003, Elsevier Science (USA). All rights reserved. Physical Forms of Gypsum-cont’d High-strength stone • Also known as densite or improved dental stone. Its strength, hardness, and dimensional accuracy make it ideal to create the dies used in the production of crowns, bridges, and indirect restorations. Copyright 2003, Elsevier Science (USA). All rights reserved. Table 47-1: Recommended Ratios of Water to Powder for Gypsum Products Copyright 2003, Elsevier Science (USA). All rights reserved. Dental Waxes Copyright 2003, Elsevier Science (USA). All rights reserved. Dental waxes Pattern Processing Impression Inlay boxing corrective Resin Sticky Bite registration Casting Carding Base plate Block out White Copyright 2003, Elsevier Science (USA). All rights reserved. utility Dental Waxes - cont’d Baseplate wax • • • • Made from paraffin or ceresin with beeswax and carnauba wax. Hard and brittle at room temperature. Supplied in sheets. Three types: 1. Type I, which is a softer wax used for denture construction. 2. Type II, a medium-hardness wax used in moderate climates. 3. Type III, a harder wax for use in tropical climates. Copyright 2003, Elsevier Science (USA). All rights reserved. Base plate Wax-contd Uses: Used to make wax rims for edentulous patients To wax-up teeth in partial and full dentures Used to create a spacer over the cast before custom trays can be made. As a block-out wax for undercuts on casts. At times used for bite registration Presentation: It is available in sheet and ribbon form and is pink in color Copyright 2003, Elsevier Science (USA). All rights reserved. Bite Registration Wax Bite registration wax is a metal-impregnated wax in sheet form. Patient is instructed to bite down, and the wax will form an imprint of the teeth. Use: It is used to record the occlusal relationships between a patient's opposing arches and to later transfer this relationship to the cast for articulation. Often without this record, it is impossible for the dentist or the laboratory technician to properly occlude the patient's cast. Copyright 2003, Elsevier Science (USA). All rights reserved. Casting wax Makeup is paraffin, ceresin, beeswax, and Copyright 2003, Elsevier Science (USA). All rights reserved. resins. Supplied in sheets of various thicknesses. Used: Used for single-tooth indirect restorations, fixed bridges, and casting metal portions of a partial denture Used for thin sections of certain partial denture and crown and bridge patterns. They are convenient in the preparation of copings or clasps requiring uniformly thin regions Inlay wax Uses: For the preparation of inlay partners, crowns, bridges using the lost wax technique. Either in the mouth by direct technique or on a model or die cast which is cast out from an impression For wax up procedures-diagnostic wax up Properties Have low thermal conductivity Have the correct flow properties Should be colored usually blue or green i.e. to contrast with oral tissues Should be easy to curve without flecking or chipping Shouldn't leave any residue on the mould. Copyright 2003, Elsevier Science (USA). All rights reserved. Carding and boxing in wax Boxing wax Soft pliable wax with a smooth and 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 it up Properties Has high flow valve at room temperature Its easily molded without the need of heating Carding wax Uses: Used by manufacturers to attach artificial teeth to the mounts on which are supplied. Copyright 2003, Elsevier Science (USA). All rights reserved. Sticky Wax Supplied in sticks or blocks. Main ingredients are beeswax paraffin, and resin. The resin gives the wax its adhesiveness and hardness. Colors are orange and the darker shades of blue, red, and violet Very brittle wax, but when heated, it becomes very tacky. An important requirement of sticky wax is that it must break under pressure rather than bend or distort. Use: This property makes it useful for holding the parts of a broken denture together so that it can be repaired. Useful when creating a wax pattern or joining acrylic resin together. Copyright 2003, Elsevier Science (USA). All rights reserved. Utility Wax Supplied in different forms depending on its use. May be red or colorless wax that comes in rope form Its makeup is beeswax, petrolatum, and other soft waxes. It is extremely pliable and tacky at room temperature, making it usable without heating. Use: Extend the borders of an impression tray. Main use is in beading (curbing) impressions before boxing and pouring. It can also be used on the impressions trays to avoid the flow of impression material to the back of the throat and to avoid injury to the soft tissue Cover brackets in orthodontic treatment Copyright 2003, Elsevier Science (USA). All rights reserved. Indicator Wax Indicator wax is usually green in color and is coated with a water soluble adhesive on one side. Use: It is used for registering occlusal contacts on natural teeth, individual restorations, FPDs, RPDs, and CDs. It is sometimes used by the dentist to evaluate high spots on restorations. Copyright 2003, Elsevier Science (USA). All rights reserved.