Impression Materials Chapter 46 Copyright 2009 2006 by

Chapter 46 Lesson 46. 1 Copyright © 2009, 2006 by Saunders, an imprint of

Learning Objectives Pronounce, define, and spell the Key Terms. List the three types of impressions taken in a dental office. Describe the types of impression trays and their characteristics of use. (Cont’d) Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Learning Objectives (Cont’d) Discuss hydrocolloid impression materials and their uses, mixing techniques, and application. Mix alginate impression material at a competent level. Take maxillary and mandibular preliminary impression at a competency level. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Introduction Impression materials are used to obtain an impression of teeth, the surrounding oral tissues, or both. Impressions are a negative reproduction of dental structures. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Preliminary Impressions Taken either by the dentist or the expandedfunction dental assistant Used for the making of: Diagnostic models Ø Custom trays Ø Provisional coverage Ø Orthodontic appliances Ø Pretreatment and posttreatment records Ø Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Final Impressions Taken by the dentist The most accurate reproduction of the teeth and surrounding tissues Used to make: Indirect restorations Ø Partial or full dentures Ø Implants Ø Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Fig. 46 -10 Example of a final impression. Copyright © 2009, 2006 by Saunders,

Bite Registrations Taken by the dentist or dental assistant A reproduction of the occlusal relationship between the maxillary and mandibular teeth Provide an accurate registration of the patient’s centric relationship between the maxillary and mandibular arches Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Fig. 46 -16 Example of a bite registration. (Courtesy of 3 M Dental Products,

Impression Trays Must be sufficiently rigid to: Carry the impression material into the oral cavity Ø Hold the material in close proximity to the teeth Ø Avoid breaking during removal Ø Prevent warping of the completed impression Ø Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Characteristics of Impression Trays Quadrant tray Ø Section tray Ø Covers the entire arch Perforated tray Ø Covers the anterior portion of the arch Full-arch tray Ø Covers one half of the arch Has holes in the tray to create a mechanical lock to hold the material in place Smooth tray Ø Interior painted or sprayed with an adhesive to hold the impression material Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Fig. 46 -1 Types of stock trays. Copyright © 2009, 2006 by Saunders, an

Fig. 46 -3 Examples of quadrant, section, and full-arch impression trays. Copyright © 2009,

Tray-Selection Criteria Must feel comfortable to the patient Should extend slightly beyond the facial surfaces of the teeth Should extend approximately 2 to 3 mm beyond the third molar, retromolar, or tuberosity area of the arch Depth to allow 2 to 3 mm of material between the tray and incisal or occlusal edges of the teeth Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Tray Adhesives VPS adhesives (blue) Ø Rubber base adhesive (brown) Ø For polyvinyl siloxane and polyether impression materials. Used with rubber base impression materials. Silicone adhesive (orange-pink) Ø Used with silicone impression materials. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Hydrocolloid Impression Materials These materials are used to obtain preliminary and final impressions. Hydro mean “water. ” Colloid means “gelatin substance. ” Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Irreversible Hydrocolloid Material cannot return to a solid state after it becomes a gel. Ø Alginate is the irreversible hydrocolloid most widely used to take preliminary impressions. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Makeup of Alginate Potassium alginate Ø Calcium sulfate Ø Comes from seaweed; also used in foods such as ice cream as a thickening agent Reacts with the potassium alginate to form the gel Trisodium phosphate Added to slow the reaction time for mixing. Ø (Cont’d) Ø Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Makeup of Alginate (Cont’d) Diatomaceous earth Ø Zinc oxide Ø A filler that adds bulk to the material Adds bulk to the material Potassium titanium fluoride Ø Added so as not to interfere with the setting and surface strength Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Physical Phases of Alginate First phase Ø In the sol (as in solution) phase, the material is in a liquid or semiliquid form. Second phase Ø In the gel phase, the material is semisolid, similar to a gelatin dessert. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Packaging and Storing of Alginate* Containers Premeasured packages *The shelf life of alginate is approximately 1 year. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Fig. 46 -5 Packaging of alginate. Copyright © 2009, 2006 by Saunders, an imprint

Cause for Distortion and Dimensional Change Imbibition Ø Alginate impression stored in water or a very wet paper towel will absorb the additional water and expand. Syneresis Ø If an alginate impression remains in the open air, its moisture will evaporate, causing the impression to shrink and distort. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Alginate Settings Normal-set alginate Ø Fast-set alginate Ø Working time of 1¼ minutes and a setting time of 1 to 2 minutes Working time Ø Working time of 2 minutes and a setting time of up to 4½ minutes after mixing The time allowed for mixing the alginate, loading the tray, and positioning the tray in the patient's mouth Setting time Ø The time required for the chemical action to be completed. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Altering the Setting Time of Alginate Cooler water can increase the setting time if additional time is needed for the procedure. Warmer water can reduce or shorten the setting time of the procedure. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Water-to-Powder Ratio Adult mandibular impression Ø Two scoops of powder and two measures of water Adult maxillary impression Ø Three scoops of powder and three measures of water Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Fig. 46 -6 A plastic scoop and plastic cylinder are supplied with alginate. Copyright

Taking an Alginate Impression Explain the procedure to the patient: The material will feel cold, there is no unpleasant taste, and the material will set quickly. Ø Breathe deeply through your nose to help relax and feel more comfortable. Ø Use hand signals to communicate any discomfort. Ø Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

An Acceptable Alginate Impression The impression tray is centered. The "peripheral roll, " including all of the vestibular areas, is completed. The tray is not "overseated. " The impression is free of tears or voids. Sharp anatomic detail of all teeth and soft tissues is captured. The retromolar area, lingual frenum, tongue space, and mylohyoid ridge are reproduced in the mandibular impression. The hard palate and tuberosities are recorded in the maxillary impression. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Fig. 46 -7 How an impression must appear. Copyright © 2009, 2006 by Saunders,

Reversible Hydrocolloid This impression material changes its physical state from a sol to a gel and then back to a sol. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Chemical Makeup of Reversible Hydrocolloid 85% water 13% agar Ø Agar is an organic substance derived from seaweed. Additional chemical modifiers are added to improve the substance’s handling characteristics. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Conditioning Bath for Reversible Hydrocolloid Three compartments 1. A “conditioner” bath liquefies the semisolid material at 212° F and is then cooled to 150° F. 2. A “storage” bath, readies the material for the impression in its tubes. 3. A “tempering” bath keeps material at 110° F in the syringe and tray. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Types of Reversible Hydrocolloid Tray material Ø Packaged in plastic tubes, each with enough material to fill a water-cooled full-arch tray Syringe material Ø Packaged in plastic or glass cartridges that fit a syringe or in preloaded syringes or preformed sticks that are used to refill special hydrocolloid inlay syringes. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Application of Reversible Hydrocolloid Impression Material 1. 2. 3. A stock water-cooled tray is selected. Plastic stops are placed in the tray. Tubing is connected to the tray and to the water outlet for drainage. 4. The material is liquefied and moved to the storage bath. 5. The light-bodied material is placed in the syringe, and heavy-bodied material is placed in the tray. 6. The light-bodied material is expressed around the prepared tooth, and the dentist seats the tray. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Chapter 46 Lesson 46. 2 Copyright © 2009, 2006 by Saunders, an imprint of

Learning Objectives Discuss elastomeric impression materials and their uses, mixing techniques, and application. Competently mix a paste final impression material. Competently prepare an automix impression material. (Cont’d) Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Learning Objectives (Cont’d) Describe the importance of the occlusal registration and its use in a procedure. Take a wax bite. Prepare and assist in a closed-bite registration procedure. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Elastomeric Impression Materials Elastomeric impression materials are used when an extremely accurate impression is essential. The term elastomeric means “having elastic or rubberlike qualities. ” Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Characteristics of Elastomeric Impression Materials Base Ø Packaged as a: • Paste in a tube • Cartridge • Putty in a jar Catalyst Ø “Accelerator” packaged as a: • Paste in a tube • Cartridge • Liquid in a bottle with a dropper top Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Forms of Elastomeric Materials Light-bodied Also referred to as syringe type or wash type Ø Used because it can flow into and around the details of the prepared tooth Ø Placed on and immediately around the prepared teeth with the use of a special syringe or extruder Ø (Cont’d) Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Forms of Elastomeric Materials (Cont’d) Regular and heavy-bodied Ø Also referred to as “tray-type” materials, they are much thicker. As the name implies, they are used to fill the tray. Their stiffness helps force the lightbodied material into close contact with the prepared teeth and surrounding tissues to ensure a more accurate impression of the details of a preparation. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Basic Impression Technique 1. 2. 3. 4. 5. 6. 7. The material selected depends on the dentist’s preference and the type of impression required for the procedure. The dentist prepares the tooth or teeth for the impression. The light-bodied material is prepared and loaded into the syringe and transferred to the dentist. The dentist places the light-bodied material over and around the prepared teeth and on the surrounding tissues. The heavy-bodied material is prepared and loaded into the tray and transferred to the dentist. When the impression material has reached its final set, the impression is removed and inspected for accuracy. The impression is disinfected, placed in a biohazard bag, labeled, and readied for the laboratory technician. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Curing Stages of Elastomeric Materials Initial set Ø Final set Ø The first stage results in stiffening of the paste without the appearance of elastic properties. The material may be manipulated only during this first stage. The second stage begins with the appearance of elasticity and proceeds through a gradual change to a solid rubberlike mass. The material must be in place in the mouth before the elastic properties of the final set begin to develop. Final cure Ø The last stage takes 1 to 24 hours. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Types of Elastomeric Materials Polysulfide Polyether Silicone Polyvinyl siloxane Copyright © 2009, 2006 by

Polysulfide Impression Material Chemical makeup Base: mercaptan polysulfide Ø Crosslinking agent: sulfur, lead peroxide, or both Ø Catalysts: copper hydroxides, zinc peroxide, organic hydrogen peroxide Ø Fillers: zinc sulfate, lithopone, or calcium sulfate dihydrate Ø Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Manipulation and Technique Considerations for Polysulfide Material Dispense pastes at the top of the mixing pad. Mix pastes with the tip of a spatula to incorporate the material first. Transfer the material to the fresh surface of the mixing pad. Water, saliva, and blood affect polysulfide material. The impression should be removed quickly after setting; do not rock the tray. The adhesive must be thin and dry before the impression material is added. Wait 20 to 30 minutes before pouring the impression to allow stress relaxation to occur in the material. Be careful to avoid glove-powder contamination. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Polyether Impression Material Chemical makeup Base: polyether Ø Crosslinking agent: sulfate Ø Catalysts: glycol-based plasticizers Ø Filler: silica Ø Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Manipulation and Technique Considerations for Polyether Material The material is very stiff, making it difficult to remove without rocking. When removing the impression, break the seal and rock it slightly to prevent tearing. Water, saliva, and blood affect polyether material. Added moisture will increase the impression’s marginal discrepancy. Increased water absorption occurs if a thinning agent is used. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Silicone Impression Material Chemical makeup Base: poly dimethyl siloxane Ø Crosslinking agent: alkyl orthosilicate or organo hydrogen siloxane Ø Catalyst: organo tin compounds Ø Filler: silica Ø Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Manipulation and Technique Considerations for Silicone Material The material has a limited shelf life. The tray requires a special tray adhesive. Silicone material is not subject to syneresis or imbibition, but it does respond with shrinkage over time. The material is more flexible, so the more chance of distortion during removal is greater. Wait 20 to 30 minutes before pouring of models for stress relaxation to occur. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Polyvinyl Siloxane Impression Material Chemical makeup Base: silicone polymer Ø Catalyst: chloroplatinic acid Ø Filler: silica Ø Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Manipulation and Technique Considerations for Polyvinyl Siloxane Material For dimensional stability, this is the best impression material. Pouring of the model can be delayed as long as 7 to 10 days. Stiffness of the material makes removal of the tray difficult. The material is dispensed with the use of an auto-mixing unit and mixing tips. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Occlusal Registration Occlusal registration is an accurate registration of the normal centric relationship of the maxillary and mandibular arches. Also commonly referred to as the bite registration. Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Types of Occlusal Registration Wax bite The wax bite is useful when the diagnostic casts are trimmed. Ø The most common technique involves the use of a softened baseplate wax. Ø Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Fig. 46 -17 Wax bite registration. Copyright © 2009, 2006 by Saunders, an imprint

Types of Occlusal Registration Polysiloxane bite-registration paste: Supplied both as a paste system and also as cartridges Ø Fast-setting Ø No resistance to biting forces Ø No odor or taste for the patient Ø Gains dimensional stability over time Ø Convenient to use Ø (Cont’d) Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Types of Occlusal Registration (Cont’d) Zinc oxide–eugenol (ZOE) bite-registration paste ZOE paste offers little or no resistance to bite closure and is fast-setting material. Ø The material is supplied in a paste system and dispensed onto a paper pad, mixed, and placed on a gauze tray for the patient to bite into. Ø Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.