Dental Assistant Instruction Pack 5 PDF

Dental Assistant Instruction Pack 5 Lessons 27-31 0204551LB05B-74 Dental Assistant Instruction Pack 5 Lesson 27—Prosthodontics Lesson 28—Periodontics Lesson 29—Endodontics Lesson 30—The Dental Assistant’s Guide to Law and Ethics Lesson 31—Practicum No part of this document may be reproduced or transmitted in any form or by any means, electronic or mechanical, for any purpose, without the express written permission of U.S. Career Institute. Copyright © 2009-2024, U.S. Career Institute. All Rights Reserved. 0204551LB05B-74 Acknowledgments Margaret Graham, M.Ed., Author Sheila D. McCray, M.S., CCS, CCS-P, Author Martha Roden, B.S., Author Celeste Yeik, AAS, Subject Matter Expert Editorial Staff Janet Perry, B.A., Vice President of Academics and Compliance Brenda Blomberg, B.A., CPC, Curriculum Department Manager Christopher Pimental, B.A., Project Manager Julia Bauernfeind, B.S., Editorial Assistant Jane Bullinger, Editorial Assistant Jessica Babb-Raymundo, B.A., Graphic Designer U.S. Career Institute Fort Collins, CO 80525 www.uscareerinstitute.edu Biographies Margaret Graham, M.Ed. Margaret Graham is an experienced educational writer and editor with more than 30 years of experience. Sheila D. McCray, M.S., CCS, CCS-P Sheila McCray is an experienced instructional designer, writer and medical coder. Sheila earned her master’s degree Instructional and Performance Technology from Boise State and a bachelor’s in Journalism from Temple University. Martha Roden, B.S. With a bachelor’s degree in Nutrition and Natural Resources, Martha Roden started her career as a nutritionist, explaining vitamins, nutrition and diet to her clients. A chance conversation with a client led her to a job as an engineering assistant and a technical writer. Next, she moved into technical training to get firsthand feedback from people regarding her explanation skills. However, teaching people to use software made her realize how difficult it was to use, so Martha moved into the usability profession—helping design software that was intuitive and easy-to-use. She’s definitely had a dynamic career, but everything she’s done has focused on helping people “find what they need and understand what they read.” Celeste Yeik, AAS Celeste graduated from Laramie County Community College in 2006 with her AAS degree in Dental Hygiene. She serves as the SME of dental assisting with U.S. Career Institute. Celeste also works as a full time clinical hygienist for Peak Dental Services where she acts as a Lead Hygiene Mentor. Celeste resides in Colorado and enjoys spending time outdoors with her husband Dustin and their three daughters. Table of Contents Lesson 27: Prosthodontics Step 1: Learning Objectives............................................................................................................................................. 1 Step 2: Lesson Preview..................................................................................................................................................... 1 Step 3: What Is Prosthodontics?..................................................................................................................................... 2 The Dental Assistant’s Role in Prosthodontics.............................................................................................. 3 Equipment and Instruments Used in Prosthodontics.................................................................................. 3 Step 4: Fixed Prosthodontics........................................................................................................................................... 6 Advantages of Fixed Prosthetic Devices......................................................................................................... 7 Indications and Contraindications.................................................................................................................. 7 Fixed Prosthodontic Treatment: Crowns....................................................................................................... 7 Step 5: Practice Exercise 27-1......................................................................................................................................... 8 Step 6: Review Practice Exercise 27-1.......................................................................................................................... 10 Step 7: Prosthetics and Materials.................................................................................................................................. 11 Cerec Crowns................................................................................................................................................... 11 Fixed Prosthodontic Treatment: Bridges...................................................................................................... 12 Fixed Prosthodontic Treatment: Inlays, Onlays and Veneers.................................................................... 14 Fixed Prosthodontic Treatment: Dental Implants....................................................................................... 16 Step 8: Provisional Coverage......................................................................................................................................... 18 Types of Provisional Coverage....................................................................................................................... 18 Step 9: Practice Exercise 27-2....................................................................................................................................... 19 Step 10: Review Practice Exercise 27-2........................................................................................................................ 22 Step 11: Fixed Prosthodontic Procedures................................................................................................................... 23 Procedure: Cast Crown................................................................................................................................... 25 Procedure: Bridge............................................................................................................................................ 31 Procedure: Inlays and Onlays........................................................................................................................ 33 Procedure: Indirect Veneers........................................................................................................................... 33 Procedure: Implant Surgery........................................................................................................................... 34 Step 12: Virtual Flashcard............................................................................................................................................. 35 Step 13: Practice Exercise 27-3..................................................................................................................................... 35 Step 14: Review Practice Exercise 27-3........................................................................................................................ 39 Step 15: Removable Prosthodontics............................................................................................................................. 40 Reasons to Prescribe Removable Prostheses................................................................................................ 40 Things to Consider.......................................................................................................................................... 41 Dental Assistant Partial Denture................................................................................................................................................. 42 Full Denture..................................................................................................................................................... 43 Overdenture..................................................................................................................................................... 44 Immediate Denture......................................................................................................................................... 44 Step 16: Removable Prosthodontic Procedures.......................................................................................................... 44 Procedure: Partial Denture............................................................................................................................. 44 Procedure: Full Denture................................................................................................................................. 45 Step 17: Virtual Flashcard............................................................................................................................................. 46 Step 18: A Word on Disinfecting Impressions and Appliances................................................................................ 46 Step 19: Practice Exercise 27-4..................................................................................................................................... 47 Step 20: Review Practice Exercise 27-4........................................................................................................................ 50 Step 21: Why This Matters............................................................................................................................................ 52 Step 22: Summary........................................................................................................................................................... 53 Step 23: Journal Entry.................................................................................................................................................... 53 Step 24: Quiz 27.............................................................................................................................................................. 53 Lesson 28: Periodontics Step 1: Learning Objectives............................................................................................................................................. 1 Step 2: Lesson Preview..................................................................................................................................................... 1 Step 3: What Is Periodontics?......................................................................................................................................... 2 Step 4: The Periodontal Office........................................................................................................................................ 3 The Dental Assistant’s Role in Periodontics................................................................................................... 3 Step 5: How Is Periodontal Disease Classified?............................................................................................................ 6 Necrotizing Periodontal Disease..................................................................................................................... 6 Periodontitis as a manifestation of systemic diseases................................................................................... 7 Periodontitis....................................................................................................................................................... 8 Classification Factors........................................................................................................................................ 8 Stages and Grades of Severity.......................................................................................................................... 8 Step 6: Practice Exercise 28-1....................................................................................................................................... 10 Step 7: Review Practice Exercise 28-1.......................................................................................................................... 13 Step 8: The Importance of the Periodontal Exam—A Review................................................................................. 14 Medical and Dental History........................................................................................................................... 15 Radiographic Exam......................................................................................................................................... 16 Visual Exam...................................................................................................................................................... 17 Periodontal Probing........................................................................................................................................ 17 Dental Exam..................................................................................................................................................... 18 VI 0204551LB05B-74 Table of Contents Step 9: Practice Exercise 28-2....................................................................................................................................... 18 Step 10: Review Practice Exercise 28-2........................................................................................................................ 20 Step 11: After the Exam—Nonsurgical Periodontal Treatment............................................................................... 21 Instruments Used in Non-surgical Periodontal Treatment....................................................................... 22 Dental Prophylaxis.......................................................................................................................................... 24 Scaling and Root Planing............................................................................................................................... 25 Gingival Curettage........................................................................................................................................... 26 Occlusal Adjustment....................................................................................................................................... 26 Administer Antibiotics................................................................................................................................... 27 Step 12: Practice Exercise 28-3..................................................................................................................................... 28 Step 13: Review Practice Exercise 28-3........................................................................................................................ 31 Step 14: Surgical Periodontal Treatments................................................................................................................... 32 Instruments Used in Surgical Periodontal Treatment............................................................................... 32 Your Role in Periodontal Surgery.................................................................................................................. 33 Excisional Surgery—Gingivectomy and Gingivoplasty.............................................................................. 33 Bone Grafting................................................................................................................................................... 35 Crown Lengthening........................................................................................................................................ 35 Soft Tissue Grafts............................................................................................................................................. 35 Osseous Surgery—Osteoplasty and Ostectomy........................................................................................... 35 Laser Surgery.................................................................................................................................................... 36 Step 15: Postoperative Procedures............................................................................................................................... 36 Periodontal Dressings..................................................................................................................................... 37 Periodontal Maintenance............................................................................................................................... 37 Step 16: Practice Exercise 28-4..................................................................................................................................... 38 Step 17: Review Practice Exercise 28-4........................................................................................................................ 41 Step 18: Why This Matters............................................................................................................................................ 42 Step 19: Summary........................................................................................................................................................... 43 Step 20: Journal Entry.................................................................................................................................................... 43 Step 21: Quiz 28.............................................................................................................................................................. 43 Endnotes........................................................................................................................................................... 44 Lesson 29: Endodontics Step 1: Learning Objectives............................................................................................................................................. 1 Step 2: Lesson Preview..................................................................................................................................................... 1 Step 3: What Is Endodontics?......................................................................................................................................... 2 0204551LB05B-74 VII Dental Assistant Step 4: The Dental Assistant’s Role in Endodontics..................................................................................................... 2 Step 5: Instruments and Materials Used in Endodontics............................................................................................ 3 Specialized Instruments.................................................................................................................................... 4 Specialized Materials......................................................................................................................................... 7 Step 6: Practice Exercise 29-1......................................................................................................................................... 9 Step 7: Review Practice Exercise 29-1.......................................................................................................................... 14 Step 8: Obtaining a Diagnosis—the Endodontic Examination................................................................................ 15 Percussion and Palpation................................................................................................................................ 16 Sensitivity to Temperature.............................................................................................................................. 17 Electric Pulp Test............................................................................................................................................. 17 Radiographs...................................................................................................................................................... 18 Step 9: The Diagnosis—Conditions of the Pulp and Radicular Tissue................................................................... 18 Step 10: Endodontic Therapies..................................................................................................................................... 19 Pulp Capping.................................................................................................................................................... 19 Pulpotomy........................................................................................................................................................ 19 Pulpectomy....................................................................................................................................................... 20 Step 11: Surgical Endodontics...................................................................................................................................... 21 Apicoectomy..................................................................................................................................................... 22 Apical Curettage.............................................................................................................................................. 22 Retrograde Restoration................................................................................................................................... 22 Step 12: Practice Exercise 29-2..................................................................................................................................... 22 Step 13: Review Practice Exercise 29-2........................................................................................................................ 25 Step 14: Why This Matters............................................................................................................................................ 26 Step 15: Summary........................................................................................................................................................... 26 Step 16: Journal Entry.................................................................................................................................................... 27 Step 17: Quiz 29.............................................................................................................................................................. 27 Endnotes........................................................................................................................................................... 27 Lesson 30: The Dental Assistant’s Guide to Law and Ethics Step 1: Learning Objectives............................................................................................................................................. 1 Step 2: Lesson Preview..................................................................................................................................................... 1 Step 3: The Law and Dentistry........................................................................................................................................ 2 How Can You Tell the Difference between One Law and Another?.......................................................... 2 Step 4: Dental Practice Acts............................................................................................................................................ 4 Typical Features of Dental Practice Acts........................................................................................................ 4 Who Creates and Interprets States’ Dental Practice Acts?........................................................................... 5 VIII 0204551LB05B-74 Table of Contents It’s Important to Know Your State’s Regulations............................................................................................ 5 Step 5: Two Key Concepts—Malpractice and Risk Management.............................................................................. 5 Malpractice......................................................................................................................................................... 5 Step 6: Practice Exercise 30-1......................................................................................................................................... 7 Step 7: Review Practice Exercise 30-1............................................................................................................................ 9 Step 8: Informed Consent.............................................................................................................................................. 10 Documentation for Informed Consent........................................................................................................ 11 Informed Refusal............................................................................................................................................. 12 What about Children?..................................................................................................................................... 12 Step 9: Reporting Abuse................................................................................................................................................ 12 Child Abuse and Neglect................................................................................................................................ 12 Abuse and Neglect in Elders.......................................................................................................................... 14 Step 10: The Good Samaritan Law............................................................................................................................... 14 Step 11: The Americans with Disabilities Act............................................................................................................ 14 Step 12: Code of Ethics.................................................................................................................................................. 15 The Dental Assistant’s Code of Ethics.......................................................................................................... 16 Ethical Dilemmas............................................................................................................................................ 16 Step 13: Practice Exercise 30-2..................................................................................................................................... 18 Step 14: Review Practice Exercise 30-2........................................................................................................................ 19 Step 15: Why This Matters............................................................................................................................................ 20 Step 16: Summary........................................................................................................................................................... 20 Step 17: Journal Entry.................................................................................................................................................... 21 Step 18: Quiz 30.............................................................................................................................................................. 21 Endnotes........................................................................................................................................................... 21 Lesson 31: Practicum Step 1: Practicum Preview............................................................................................................................................... 1 Step 2: Quiz 31.................................................................................................................................................................. 1 0204551LB05B-74 IX Dental Assistant X 0204551LB05B-74 Lesson 27 Prosthodontics Step 1: Learning Objectives When you have completed the instruction in this lesson, you will be trained to: Define and describe key prosthodontic terms, equipment and materials. Describe the uses, indications and contraindications for fixed prosthodontics. Describe the components and types of materials used to create crowns, bridges, inlays and onlays, veneers, implants and provisional coverage. Describe the uses, indications and contraindications for removable prosthodontics. Describe the purpose, function and procedures to place various types of dentures. Outline the dental assistant’s role in prosthodontic procedures. Step 2: Lesson Preview Many types of patients will benefit from prosthodontic care. As a dental assistant, you’ll help people who have decayed, damaged or missing teeth to regain their chewing function, normal speaking ability and confidence. In this lesson, you’ll learn about the field of prosthodontics—the specialized field of dentistry that involves restoration and replacement of missing teeth. You’ll explore various permanent restorations such as crowns, bridges, inlays, onlays and veneers. As you learn about each material, you will also become familiar with the procedures involved to fabricate and place those restorations. Before a permanent restoration can be placed, patients must often wear provisional devices to maintain oral function until the finished product is ready. You’ll also learn about these temporary solutions to provide comfort and function to the patient. You’ll also explore removable appliances, such as full and partial dentures, and the procedures involved to fabricate and fit them. The final section of this lesson will familiarize you with dental implants, which replace both the tooth and the root. Dental Assistant Most importantly, throughout this lesson you’ll gain an understanding of your role in assisting during prosthodontist treatments. You’ll learn how to assist the dentist in various procedures, including preparing and delivering a crown, bridge or other cast restoration, making and seating a temporary crown and placing and removing gingival retraction cord. Prosthodontics is an interesting and exciting field, so let’s get started! Step 3: What Is Prosthodontics? Prosthodontics is the branch of dentistry that specializes in the replacement or restoration of damaged or missing teeth. This is done through placing a dental prosthesis. A dental prosthesis, or prosthetic device, is an artificial tooth or other dental appliance that replaces part or all a tooth or its associated structure. Partial dentures There are three types of prosthodontic treatments: Fixed prosthodontics—Involve placement of prostheses that the patient can’t remove. The most common are indirect restorations (restorations made at a lab and later cemented onto the tooth structure). These are crowns and bridges. Other restorations include inlays, onlays, veneers and implants. Provisional coverage—Is the placement of temporary prostheses while the patient waits for a permanent device. Normally considered a part of fixed prosthodontics since most patients need some kind of temporary prosthesis to protect their teeth while they wait for a crown or bridge to be made and delivered. Removable prosthodontics—Involve restoration or replacement of missing teeth with a prosthesis that the patient can remove easily. The two basic types of removable dental prosthetic devices are partial dentures and full dentures. Partial dentures, or partials, as they’re commonly called, replace one or more teeth in the same arch. Full dentures replace all the teeth in one arch. Prosthodontic dentists, or prosthodontists, are experts in dental rehabilitation. They’ve mastered many procedures, from fabricating dental restorations to surgically placing implants. 27-2 0204551LB05B-27-74 Prosthodontics Although prosthodontics is one of nine specialties recognized by the American Dental Association, most general dentists perform their own fixed and removable prosthodontic procedures with the help of a dental laboratory. The dentist determines what prosthodontic treatment a patient needs through careful intraoral examination and review of detailed medical and dental histories. Additionally, the dentist looks at current full-mouth or panoramic radiographs, photographs and diagnostic models. Diagnosis and treatment begin only after the dentist thoroughly evaluates the patient’s dental condition. The Dental Assistant’s Role in Prosthodontics The dental assistant is involved in all stages of prosthodontic treatment. To properly assist the dentist, you must understand the various types of restorations, as well as the sequence of steps in a procedure. Why? Because you’ll explain the steps of the procedure to the patient, answer patient questions, help the dentist and give post-operative and home-care instructions to the patient. Prosthodontic treatments generally require multiple visits to the dentist’s office—usually two—but as many as six or seven visits may be required. For each appointment, you’ll make sure the prosthetic device has been completed and returned from the dental laboratory. You’ll set up the room and make sure the dentist has everything she needs for that appointment. In some cases, you’ll create and place temporary restorations yourself to save the dentist time. You’ll also assist the dentist throughout each procedure. Equipment and Instruments Used in Prosthodontics You’ll be glad to hear you’re already familiar with most of the equipment, instruments and materials you’ll use during a prosthodontic procedure. The prosthodontist will need: Equipment Materials HVE Saliva ejector PPE Instruments Articulating paper and holder Various burs, stones, discs Bite-stick Periodontal probe Cord-packing instrument Scalers Forceps Scissors Handpieces Spoon Excavators Basic setup (mouth mirror, double Provisional crown ended explorer and cotton pliers) forceps Materials Air/water syringe tips Gingival retraction cord Cementation supplies HVE tip Cotton 2 × 2 gauze Local anesthetic Cotton rolls Wax wafer Floss 0204551LB05B-27-74 27-3 Dental Assistant Let’s explore the items on this list that you’ve not yet covered: gingival retraction cord, cord-packing instrument, provisional crown forceps, wax wafer. Gingival retraction involves using a chemical or nonchemical retraction cord to pull the gingiva away from the tooth. This allows professionals to take an accurate subgingival impression. A gingival retraction cord is a type of thread used to separate the tooth from the surrounding gingiva. Also known as packing cord, gingival retraction cord is available as plain (untwisted), twisted or braided. It comes in various thicknesses. Plain cord must be twisted before use. Gingival retraction cord in use Chemical retraction cords are treated with a chemical that causes the tissues to shrink, temporarily widening the sulcus. Some cords are even impregnated with chemicals that control bleeding. Nonchemical retraction cords do not contain any chemicals—the tissue is retracted physically with the cord packing instrument. As its name implies, a cord-packing instrument is designed with spatula-shaped ends that allow it to gently push cord into the sulcus around the treated tooth. Provisional crown forceps won’t damage the temporary crown. Provisional crown forceps are used during a fixed prosthodontic procedure. They are specifically designed to grip and gently apply pressure to a provisional crown. With gentle, firm pressure, the DA will be able to loosen the temporary cement and lift the provisional crown off the prepared tooth. These forceps offer superior tactile feel for the dental assistant so he can remove the provisional crown without damaging it. The crown can be reused if necessary. 27-4 0204551LB05B-27-74 Prosthodontics You will also use a wax wafer, a type of bite registration wax, to take the patient’s bite registration after the tooth has been prepped for the prosthesis. A wax wafer is typically very thin, only 1/8 inch thick. The dentist uses this to determine if enough clearance is achieved to accept the prosthesis. Tray Setup Various instruments. Each type of procedure requires a different tray setup. As the dental assistant, you will set up a tray of instruments and supplies for each appointment. In addition to the basic setup, you’ll arrange each tray setup according to the sequence of the procedure with auxiliary instruments and materials close at hand. The dentist will specify the necessary equipment, instruments and materials that she’ll need for each procedure. Tray Setup Every dentist has his own preferences regarding tray setup, but use the diagram included to guide you in general tray setup. Remember the general setup formula. From left to right on tray: 1. Basic setup 2. Examination instruments 3. Hand cutting instruments 4. Restorative and accessory instruments Group remaining instruments according to function. For example, all burs placed together. At top of tray: 1. Cotton supplies At far-right side of tray: 1. Scissors, hemostats and other hinged instruments for easy access Return instruments to their original positions after receiving them from the operator. 0204551LB05B-27-74 27-5 Dental Assistant Correct tray setup Single-use Devices and Doses During tray setups, you’ll commonly use single use items, devices or doses. A single-use device (SUD) is one you’ll use one time. It’s disposable, not meant for cleaning, for sterilizing or for other patients. You’ll use them as needed and set them up on your tray for ease of use by the dentist. As part of infection control, these single-use items help prevent cross -contamination between patients. Some examples are syringes, needles, suction tips, masks, air tips and such. You’ve learned many of these already. The same holds true for certain dental files and plastic impression trays. Also, gauze, cotton rolls and saliva ejectors are key examples. Recall, however, to set up your trays—including single-use devices—using the aseptic techniques you learned earlier. Note: You might hear some of these items called single dose use or single unit device. More important than the name is that you understand its use and purpose. Now let’s look at the field of fixed prosthodontics, including the various types of prosthetic devices, materials and procedures involved. Step 4: Fixed Prosthodontics This type of work is often referred to as “crown and bridge work” because these are the most common types of cast restorations. However, fixed prosthodontic treatments include: crowns, bridges, veneers, inlays, onlays and implants. The prostheses used are called indirect restorations because they cannot be placed in the mouth immediately after the tooth is prepared. Instead, the dentist takes impressions of the prepared teeth and surrounding area and sends the impressions to a dental laboratory where they’ll use them to fabricate, or cast, the fixed prosthesis, which explains why these prostheses are also called cast restorations. Cast restorations are permanent and can’t be reshaped. They also have superior strength and excellent aesthetics. After delivery, the dentist prepares, cleans and dries the tooth structure so he can perfectly seat the cast restoration. Then, the dentist bonds or cements the restoration in place. 27-6 0204551LB05B-27-74 Prosthodontics Advantages of Fixed Prosthetic Devices Fixed prosthodontic treatment offers several advantages to patients with missing teeth or tooth structures. The restoration is secure in the mouth; it looks good and it restores function for many years. Indirect restorations can also: Restore efficient chewing functions Improve the patient’s appearance and self-esteem Improve speech that has been impaired by dental problems Promote good oral hygiene and dental health Prevent further movement of the teeth that can lead to tooth loss Indications and Contraindications Patients with one or two adjacent teeth missing in the same arch are good candidates for crowns or bridges. However, not all patients are viable candidates for fixed prosthodontic treatment. For example, some patients need to have periodontal or orthodontic treatment to improve the health of the supportive tissues before prosthodontic treatment can be considered. Indications and Contraindications for Crowns or Bridge Work Indications Contraindications Crowns and bridges are a good option Crowns and bridges are NOT an option for a patient with: for a patient with: Healthy tissues Diseased or missing supportive tissues Healthy abutment teeth Unsuitable abutment teeth Good overall health Poor overall health Skills and motivation to maintain good Lack of motivation to maintain a oral hygiene prosthesis The dentist determines the type of prosthodontic treatment based on the extent of tooth orientation and location, tooth destruction and the condition of neighboring teeth. In the next steps of this lesson, you’ll explore the various types of fixed prosthodontic treatments, starting with crowns. Fixed Prosthodontic Treatment: Crowns Crowns are the most common type of fixed prosthodontic treatment. Crowns cover broken teeth or teeth with extensive decay. Because the cast crown cannot be reshaped, the dentist must prepare the tooth structure to allow the crown to be seated in place with only minor adjustments. The dentist then covers the prepared tooth with the crown, which is anatomically shaped and fitted. 0204551LB05B-27-74 27-7 Dental Assistant Gold is generally used only for posterior crowns. Crown Shapes There are three shapes of crowns: Partial crown—This is a cast restoration that covers three or more, but not all, surfaces of the tooth. Three-quarter crown—This is commonly used on posterior teeth since it doesn’t cover the entire tooth. Instead, it covers the anatomic crown of the tooth, except for the facial or buccal portion. Full crown—This is often referred to as a full cast crown by the dentist or a “cap” by patients. It covers the entire coronal surface of the tooth. It’s typically used for a tooth that is extremely decayed or fractured and cannot be restored any other way. Sometimes the tooth is so badly damaged that retention aids are necessary to retain the full crown on the tooth. Step 5: Practice Exercise 27-1 Select the best answer from the choices provided. 1. _____ is the field of dentistry that specializes in the restoration or replacement of missing or damaged teeth. a. Orthodontics b. Prosthodontics c. Crowning d. Denture fitting 2. _____ deal(s) with restorations and prosthetic devices that the dentist cements or attaches to the teeth and the patient cannot remove. a. Provisional prosthodontics b. Prosthodontists c. Fixed prosthodontics d. Removable prosthodontics 27-8 0204551LB05B-27-74 Prosthodontics 3. _____ is the term for a temporary prosthesis the patient wears while waiting for her permanent crown or bridge. a. Master impression b. A full-metal crown c. A PFM crown d. Provisional coverage 4. Among the duties you’ll have as a prosthodontic dental assistant is to _____. a. thoroughly evaluate the patient’s dental condition b. explain the steps of the prosthodontic procedure to the patient c. perform an intraoral exam d. examine the patient’s radiographs, photographs and diagnostic models 5. Prosthodontic treatments can take anywhere from _____ visits to the dentist to complete. a. one to two b. two to four c. two to seven d. six to seven 6. _____ are fabricated in the lab based on impressions taken during an initial dental visit, and later cemented to the patient’s teeth during a second visit. a. Indirect restorations b. Direct restorations c. Full metal crowns d. Porcelain jacket crowns 7. A patient with _____ is NOT a good candidate for a bridge or crown. a. healthy abutment teeth b. a weak immune system c. good oral hygiene habits d. the skills and motivation to maintain a prosthesis 8. Partial a. Covers the anatomic crown of the tooth, except for the facial or buccal portion b. Cast crown that covers the entire coronal surface of the tooth c. Cast restoration that covers three or more surfaces of the tooth, but not all surfaces d. The strongest and most durable material for cast crowns 0204551LB05B-27-74 27-9 Dental Assistant 9. Three-quarter a. Covers the anatomic crown of the tooth, except for the facial or buccal portion b. Cast crown that covers the entire coronal surface of the tooth c. Cast restoration that covers three or more surfaces of the tooth, but not all surfaces d. The strongest and most durable material for cast crowns 10. Full crown a. Covers the anatomic crown of the tooth, except for the facial or buccal portion b. Cast crown that covers the entire coronal surface of the tooth c. Cast restoration that covers three or more surfaces of the tooth, but not all surfaces d. The strongest and most durable material for cast crowns Step 6: Review Practice Exercise 27-1 Review the answers to the Practice Exercise and use this as a study tool when preparing for your Quiz. 1. b. Prosthodontics is the field of dentistry that specializes in the restoration or replacement of missing or damaged teeth. 2. c. Fixed prosthodontics deal(s) with restorations and prosthetic devices that the dentist cements or attaches to the teeth and the patient cannot remove. 3. d. Provisional coverage is the term for a temporary prosthesis the patient wears while waiting for her permanent crown or bridge. 4. Among the duties you’ll have as a prosthodontic dental assistant is to b. explain the steps of the prosthodontic procedure to the patient. 5. Prosthodontic treatments can take anywhere from c. two to seven visits to the dentist to complete. 6. a. Indirect restorations are fabricated in the lab based on impressions taken during an initial dental visit, and later cemented to the patient’s teeth during a second visit. 7. A patient with b. a weak immune system is NOT a good candidate for a bridge or crown. 8. Partial c. Cast restoration that covers three or more surfaces of the tooth, but not all surfaces 9. Three-quarter a. Covers the anatomic crown of the tooth, except for the facial or buccal portion 10. Full crown b. Cast crown that covers the entire coronal surface of the tooth 27-10 0204551LB05B-27-74 Prosthodontics Step 7: Prosthetics and Materials Crowns are fabricated from different materials or a combination of materials. Gold is the most common material, but a crown may also have a porcelain exterior to enhance its appearance. Let’s look at the different types of crowns, based on material. A porcelain-fused-to-metal (PFM) crown Full metal crown—This is made of gold alloy, palladium, nickel alloy or chromium alloy. A full metal crown is ideal for use on the back teeth where appearance isn’t a priority. A metal crown without any porcelain is the simplest and most stable solution to restore a damaged natural tooth. When it comes to metal, gold is best because it’s strong and highly compatible with your mouth. Other metals may cause sensitivity or an allergic reaction. Porcelain-fused-to-metal (PFM) crown—This starts out as a full metal crown, but the outer surface is covered with a thin layer of porcelain that matches the color of the natural tooth. A PFM crown has two big advantages over other types of crowns: 1) it is stronger than all-porcelain crowns and 2) it looks more like a natural tooth than a full metal crown. Porcelain jacket crown—This begins with a very thin metal shell that is covered by a layer of porcelain. The porcelain is built up to provide the shading and translucence of a natural tooth. Porcelain jacket crowns are usually used on anterior teeth because they look like natural teeth. They are not as strong as PFM or full metal crowns, but anterior teeth undergo less stress so this is usually not a problem. Cerec Crowns Traditional crowns, which are lab-manufactured cast restorations, require patients to make two visits to the dentist’s office. But there is a way to receive a quality crown in a single visit. Some dentists use computer- assisted design/computer-assisted manufacture (CAD-CAM) software to design and fabricate crowns in their own offices, rather than rely on dental laboratories. The dentist mills the Cerec crown in the office to precisely fit any tooth. This may take some time, but the computer controlled milling machine uses the 3-D model created by the CAD-CAM software to create the crown. This process effectively eliminates the need for a laboratory to do the fabrication. It can be made immediately on-site in the dental office—no need for a second appointment or a temporary crown. 0204551LB05B-27-74 27-11 Dental Assistant The Cerec crown is named for CEREC, the foremost CAD-CAM software system for dental restorations. The Cerec 3-D system Cerec crowns are milled out of a single block of ceramic. Theoretically, this creates an aesthetic problem because natural teeth are not a single solid color. Rather, they have a gradation of color from the gum line to the biting edge. But some very skillful dentists have learned to use Cerec technology to create restorations that look so natural they can be used on anterior teeth. Still, there are advantages and disadvantages of choosing Cerec crowns versus lab-created cast restorations. PROS and CONS of Cerec Crowns PROS CONS Cerec crowns are made in one visit, saving The initial investment for a CEREC CAD-CAM time for both the dentist and the patient. system is quite expensive. There is no need for a temporary crown with Laboratory-made crowns offer better aesthetic a Cerec crown, which eliminates potential quality for front teeth. Since Cerec crowns discomfort and inconvenience for the are milled from a single block of ceramic, it’s patient. difficult to produce the subtle color gradients Cerec crowns are reasonably aesthetic of natural teeth. because they contain no metal. Some companies now make ceramic blocks Cerec material and technology can also with a color gradient, but it still takes a high be used for fillings. Since they are made of degree of skill and talent to create a natural- ceramic, they are more durable than typical looking result with Cerec crowns. white composite fillings. Cerec technology can save money over the long-term by avoiding lab technician fees. Fixed Prosthodontic Treatment: Bridges Sometimes, a patient has more dental damage than a crown can manage. In such a case, the dentist may decide to use a bridge. Bridges are prosthodontic devices that replace multiple missing teeth in the same arch. The two most common types of bridges are a fixed bridge and a resin-bonded bridge. 27-12 0204551LB05B-27-74 Prosthodontics Fixed Bridge A fixed bridge is a prosthesis used when one or more teeth are missing in the same arch. The bridge consists of a series of units joined together for greater strength. The number of units reflects the number of teeth involved. For example, a three-unit bridge consists of two existing teeth, one at either end of the bridge, and an artificial tooth in the middle. Bridge work The existing “anchor” teeth are called abutments or retainers. The abutment can be a titanium cylinder placed on top of a dental implant. A short bridge that replaces only one tooth has two abutments, one at each end of the bridge. Longer bridges may have several abutments at each end of the bridge. It is up to the dentist to design such a bridge taking into consideration the patient’s periodontal bone health (ideally there is no bone loss) and occlusion, which produces occlusal forces on the bridge. In any case, cast crowns can be used to strengthen the abutments. Did You Know? A good rule of thumb for longer bridges (more than one tooth missing) is to use one abutment on the posterior and a double abutment on the anterior portion of the bridge to support the missing teeth. For example, suppose teeth #19 and #20 are missing. The fixed bridge would be 18-19-20- 21-22, where #19 is a single abutment and #21 and #22 are double abutments. With longer bridges, the dentist may decide to use double abutments posteriorly and anteriorly. For example, if teeth #7, #8, #9 and #10 are missing, the fixed bridge would be 5-6-7-8-9-10-11-12, where #5 and #6 are double abutments, as are #11 and #12. 0204551LB05B-27-74 27-13 Dental Assistant An artificial tooth, or pontic, replaces a missing tooth. The artificial tooth is called a pontic. In a bridge, there must be one pontic for each missing tooth. Two common types of pontics are the hygienic (free cleansing) and cosmetic. Both pontics are rounded underneath near the gum. The hygienic pontic provides plenty of space between the pontic and the gingiva so the patient can easily clean between them with a proxy brush. A cosmetic pontic is tooth-colored and shaped like a full tooth, so there is very little space between it and the gingival tissue. The patient must use a bridge threader to clean under a cosmetic pontic. Resin-bonded Bridge A resin-bonded bridge (also known as a Maryland bridge) consists of a resin or porcelain pontic, with resin wing-like extensions from the mesial and distal sides. The dentist bonds the extensions to the lingual surfaces of the adjacent teeth. Dentists rarely use this type of bridge because it is not predictable and often needs to be re-cemented. However, when it is used, the resin-bonded bridge is used primarily on a missing front tooth. The resin-bonded bridge requires little or no reduction of anchor teeth. The dentist needs to prepare only a small amount of the linguals of the teeth on either side before taking an impression. These bridges work best when the abutment teeth are anterior, healthy teeth with no large restorations. Fixed Prosthodontic Treatment: Inlays, Onlays and Veneers Now let’s examine three additional types of cast restorations: inlays, onlays and veneers. Like crowns and bridges, these restorations are permanent and can’t be reshaped or easily removed by the patient. Inlays and Onlays Inlays and onlays are restorations that replace missing tooth structure within the tooth. They are generally used when there isn’t enough healthy tissue left in the tooth to support a regular restoration, but the tooth is not so severely damaged that a crown is necessary. They work well when tooth destruction is less than half the distance between cusp tips. 27-14 0204551LB05B-27-74 Prosthodontics Unlike regular restorations, inlays and onlays conserve natural tooth structure and strengthen, rather than weaken, teeth. Inlay—This restoration is similar to a Class II restoration. It covers the area between the cusps of the tooth on the occlusal surface, as well as some of the proximal surfaces. Onlay—This restoration covers more of the occlusal tooth surface than an inlay. It covers the area between the cusps, as well as the cusp ridges, and covers some of the proximal surfaces. However, it covers less of the tooth than a three-quarter crown. An onlay covers most of the occlusal tooth surface A variety of materials are used to cast inlays and onlays. The type of material depends on the extent of missing tooth structure and what is necessary to restore function and preserve the strength of the tooth. Although gold is the strongest material, it doesn’t match the color of the tooth. For teeth that are visible, porcelain, ceramic or composite resin work best for inlays and onlays because these materials can be matched to the color of the tooth. Veneers As you may recall from the last lesson, a veneer is a thin layer of tooth-colored composite or porcelain placed over a patient’s tooth. It’s generally used on anterior teeth to improve appearance or restore a damaged tooth structure. Dentists often use veneers when teeth are intrinsically stained (stained from within), such as in the case of tetracycline-stained teeth. Veneers also cover naturally discolored teeth or teeth marked by enamel hyperplasia or hypocalcification (too much or too little enamel development). 0204551LB05B-27-74 27-15 Dental Assistant Veneers improve the appearance of stained teeth There are two types of veneers: indirect and direct. Indirect veneers—like other indirect restorations, are fabricated in a dental laboratory, based on the impression of the tooth. The dentist must prepare the teeth and then cement the completed veneer to the prepared tooth where some tooth structure has been removed. The best indirect veneers are made of porcelain that matches the patient’s tooth color. Direct veneers—are created directly in the patient’s mouth in the dentist’s office. The dentist uses a composite resin and bonds it directly to the patient’s tooth with minimal preparation (usually just reduction of the cervical margin). Direct veneers cost less than indirect ones because they don’t involve a dental laboratory. Direct veneers are also easy to work with. However, they lack strength and tend to wear more quickly than porcelain. They generally last about five years. Fixed Prosthodontic Treatment: Dental Implants A dental implant is an artificial tooth with a root replacement. It can replace a single tooth or provide an abutment tooth to help hold bridges or dentures. Dental implants look and function more like normal teeth than prostheses. However, they are somewhat more expensive and require surgical procedures that can take up to six to nine months to heal. The most common dental implants use titanium implants that resemble a tooth root. 27-16 0204551LB05B-27-74 Prosthodontics A dental implant that replaces a single tooth is especially useful when the adjacent teeth are virgin teeth or have never had any restorations. The virgin teeth on either side of the implant remain untouched, while the implant successfully replaces a missing tooth. Otherwise, without an implant, the patient would need a bridge. This means that the two healthy abutment teeth would have to be prepped down to miniature tooth shapes and crowned—an unfortunate removal of good tooth structure. Implants are often placed to provide abutment teeth to help hold dentures. They are generally used for lower full dentures where patients have the most trouble with retention. Implants help conserve the alveolar ridge in the area of placement and are fitted with housings that snap into the denture to provide stability. Osseointegration is when living bone forms a structural and functional connection with the surface of an artificial implant or prosthesis. The bone tissue fuses with the surface of an implant or prosthesis. This creates a stable foundation for the implant and allows it to work like a tooth or bone. This process typically involves a healing period of several months. There are several types of dental implants, but the most widely accepted and successful implant today is the Osseointegrated implant. Also known as an endosteal implant, it consists of three components: Titanium implant—This resembles a tooth root with a roughened or smooth surface. It is surgically embedded in the bone. Titanium abutment screw—This is screwed into the implant after osseointegration. It has a collar that extends above the mucosa. Abutment post or cylinder—This attaches the collar of the screw to the artificial tooth or denture. Indications Implants are not for everyone. They are somewhat expensive, generally require a specialist to place them and require a longer healing time before the tooth can be restored. For those reasons, many patients still opt for fixed bridges. But for a growing number of people, implants are the treatment of choice. When properly placed, dental implants have a high success rate—over 90 percent. They can last as long as 20 years and may even last a lifetime. Implants can perform these functions: Replace one or more teeth as single units with crowns Provide support for a partial denture Increase the support, stability and patient satisfaction for a full lower denture Enhance the patient’s comfort level when chewing Increase the patient’s confidence in smiling and speaking Improve the patient’s overall psychological health Improve the aesthetic appearance of the patient’s teeth 0204551LB05B-27-74 27-17 Dental Assistant Step 8: Provisional Coverage Provisional coverage refers to a temporary crown or bridge that is cemented to a prepared tooth for a single crown or to abutment teeth for a bridge. Patients wear temporary crowns or bridges while the lab makes their permanent restorations. Provisional coverage protects the prepared teeth, maintains the patient’s appearance and prevents teeth from drifting or overeruption by retaining contact points and proper occlusion. Types of Provisional Coverage There are several types of provisional coverage available. Aluminum Crown These are thin, shell-like crowns made of a very durable medium-hard aluminum. They are used for premolars and molars where the color doesn’t matter, but strength is essential. Although they are convenient, aluminum crowns are only suitable for short-term use and are considered less satisfactory than acrylic crowns. Aluminum crowns come preformed from the manufacturer in a range of sizes. They may be anatomic or non-anatomic in appearance. Those that have anatomic features look more like real teeth and are contoured much like stainless steel crowns. Those with non-anatomic features resemble thimbles with straight sides and flat occlusal surfaces. They require additional contouring to adapt to the tooth. Both types of aluminum crowns can be filled with acrylic or composite material to get a custom fit before cementing them in place. Aluminum crowns are convenient and quick to adapt to a prepared tooth. Their soft material is easy to work with, but extreme care is required to contour them because their edges irritate soft tissue when the fit isn’t perfect. Some patients also complain of a metallic taste. Custom Acrylic Crown These crowns are commonly referred to as custom acrylic temporaries. Dentists use these custom-fitted, natural looking restorations for posterior or anterior crowns and bridges. Patients like them because they feel comfortable and look very natural. Custom crowns take a lot of time to prepare. When making a custom acrylic temporary, you must take an initial alginate impression before the dentist prepares the tooth. Acrylic resin is then placed in the preliminary alginate impression in the tooth area that will receive the provisional crown. The most common material used for provisional coverage is self-curing acrylic, either supplied in cartridges or as a liquid and powder. This type of acrylic comes in a variety of shades so it can match the shade of the adjacent teeth. Although custom acrylic temporaries take the most time to prepare, they are the most commonly used temporaries. Preformed Polycarbonate Crown Polycarbonate refers to any of a class of thermoplastic materials that has high-impact strength and is light- weight and flexible. This type of crown is tooth colored, which makes it popular for anterior teeth where appearance is important. Although polycarbonate crowns are preformed, they can be customized in various sizes to fit any anterior tooth. These crowns take little time to prepare. 27-18 0204551LB05B-27-74 Prosthodontics Preformed Polymer Crown Preformed polymer crowns are shell-like crowns that are bonded to teeth with a hybrid composite resin. They are used only for premolars and molars. They are designed with anatomic features of natural teeth and are available for single crowns and bridgework. Now that you’ve had a chance to explore the many types of fixed prosthodontics, pause for a brief review with a Practice Exercise. Step 9: Practice Exercise 27-2 Select the best answer from the choices provided. 1. Gold a. Covers the anatomic crown of the tooth, except for the facial or buccal portion b. Cast crown that covers the entire coronal surface of the tooth c. Cast restoration that covers three or more surfaces of the tooth, but not all surfaces d. The strongest and most durable material for cast crowns 2. Full metal a. Crown that’s milled from a single block of ceramic using a CAD-CAM system, and can be placed in one appointment b. Thin metal shell covered with layers of porcelain, built up to mimic the shade and translucence of a natural tooth c. Full metal crown whose surface is covered by a thin layer of porcelain d. Simplest and most stable solution to restore a damaged natural tooth 3. PFM a. Crown that’s milled from a single block of ceramic using a CAD-CAM system, and can be placed in one appointment b. Thin metal shell covered with layers of porcelain, built up to mimic the shade and translucence of a natural tooth c. Full metal crown whose surface is covered by a thin layer of porcelain d. Simplest and most stable solution to restore a damaged natural tooth 4. Porcelain jacket a. Crown that’s milled from a single block of ceramic using a CAD-CAM system, and can be placed in one appointment b. Thin metal shell covered with layers of porcelain, built up to mimic the shade and translucence of a natural tooth c. Full metal crown whose surface is covered by a thin layer of porcelain d. Simplest and most stable solution to restore a damaged natural tooth 0204551LB05B-27-74 27-19 Dental Assistant 5. Cerec a. Crown that’s milled from a single block of ceramic using a CAD-CAM system, and can be placed in one appointment b. Thin metal shell covered with layers of porcelain, built up to mimic the shade and translucence of a natural tooth c. Full metal crown whose surface is covered by a thin layer of porcelain d. Simplest and most stable solution to restore a damaged natural tooth 6. A dentist recommends a bridge when a patient _____. a. is missing one or more teeth in the same arch b. has poor oral hygiene habits c. doesn’t have suitable abutment teeth d. has diseased tissues 7. A fixed bridge consists of a number of units that represent the number of _____ involved. a. crowns b. teeth c. pontics d. fillings 8. The existing teeth that anchor the bridge are called _____, or retainers. a. crowns b. pontics c. castings d. abutments 9. A _____ is an artificial tooth in a bridge. a. pontic b. crown c. casting d. temporary 10. A _____ pontic provides a larger space between the pontic and gingiva than a _____ pontic. a. hygienic; cosmetic b. cosmetic; hygienic c. resin-bonded; Maryland d. Maryland; resin-bonded 27-20 0204551LB05B-27-74 Prosthodontics 11. A resin-bonded or Maryland bridge is not used often because it _____. a. is very hard to bond the wings of the bridge to adjacent teeth b. requires a large reduction of the anchor teeth c. is unpredictable and must often be re-cemented d. can only be used on posterior teeth with no large restorations 12. Unlike regular restorations, inlays and onlays _____ natural tooth structure. a. lighten b. darken c. weaken d. strengthen 13. An inlay _____. a. covers more of the tooth than a three-quarter crown b. covers the area of a tooth between the cusps, as well as the cusp ridges, and covers some of the proximal surfaces c. covers the entire occlusal surface of a tooth d. covers the area between the cusps of the tooth on the occlusal surface, as well as some of the proximal surfaces 14. An onlay _____. a. covers more of the tooth than a three-quarter crown b. covers the area of a tooth between the cusps, as well as the cusp ridges, and covers some of the proximal surfaces c. is similar to a Class II restoration d. covers the area between the cusps of the tooth on the occlusal surface, as well as some of the proximal surfaces 15. A(n) _____ is a thin layer of tooth-colored composite or porcelain placed over a patient’s tooth for cosmetic purposes. a. inlay b. onlay c. veneer d. opaquer 16. Lisa visits her dentist to discuss the tetracycline stains on her teeth. The stains embarrass her. Her dentist would likely recommend that Lisa get _____. a. veneers b. inlays c. onlays d. a crown 0204551LB05B-27-74 27-21 Dental Assistant 17. A(n) _____ consists of a titanium implant, titanium abutment screw and an abutment post or cylinder. a. indirect veneer b. direct veneer c. osseointegrated implant d. resin-bonded bridge 18. _____ refers to the growth of bone tissue around surgically implanted devices. a. Osseointegration b. Acclimation c. Overgrowth d. Intrinsic 19. Provisional coverage performs all of these functions EXCEPT _____. a. protects the prepared teeth b. maintains the patient’s appearance c. allows the patient to function normally for up to six months d. prevents teeth from drifting or overeruption by maintaining contact points and proper occlusion 20. Dentists use _____ for posterior or anterior crowns and bridges. Patients like them because they feel comfortable and look very natural. a. polymer crowns b. aluminum crowns c. polycarbonate crowns d. custom acrylic temporaries Step 10: Review Practice Exercise 27-2 Review the answers to the Practice Exercise and use this as a study tool when preparing for your Quiz. 1. Gold d. The strongest and most durable material for cast crowns 2. Full metal d. Simplest and most stable solution to restore a damaged natural tooth 3. PFM c. Full metal crown whose surface is covered by a thin layer of porcelain 4. Porcelain jacket b. Thin metal shell covered with layers of porcelain, built up to mimic the shade and translucence of a natural tooth 5. Cerec a. Crown that’s milled from a single block of ceramic using a CAD-CAM system, and can be placed in one appointment 6. A dentist recommends a bridge when a patient a. is missing one or more teeth in the same arch. 27-22 0204551LB05B-27-74 Prosthodontics 7. A fixed bridge consists of a number of units that represent the number of b. teeth involved. 8. The existing teeth that anchor the bridge are called d. abutments, or retainers. 9. A a. pontic is an artificial tooth in a bridge. 10. A a. hygienic pontic provides a larger space between the pontic and gingiva than a cosmetic pontic. 11. A resin-bonded or Maryland bridge is not used often because it c. is unpredictable and must often be re-cemented. 12. Unlike regular restorations, inlays and onlays d. strengthen natural tooth structure. 13. An inlay d. covers the area between the cusps of the tooth on the occlusal surface, as well as some of the proximal surfaces. 14. An onlay b. covers the area of a tooth between the cusps, as well as the cusp ridges, and covers some of the proximal surfaces. 15. A c. veneer is a thin layer of tooth-colored composite or porcelain placed over a patient’s tooth for cosmetic purposes. 16. Lisa visits her dentist to discuss the tetracycline stains on her teeth. The stains embarrass her. Her dentist would likely recommend that Lisa get a. veneers. 17. An c. osseointegrated implant consists of a titanium implant, titanium abutment screw and an abutment post or cylinder. 18. a. Osseointegration refers to the growth of bone tissue around surgically implanted devices. 19. Provisional coverage performs all of these functions EXCEPT c. allows the patient to function normally for up to six months. 20. Dentists use d. custom acrylic temporaries for posterior or anterior crowns and bridges. Patients like them because they feel comfortable and look very natural. Step 11: Fixed Prosthodontic Procedures Now that you’re familiar with the types of fixed prosthodontics you’ll be working with, let’s step into the treatment area to find out what you’ll be doing during a prosthodontic procedure. Treatment begins when a problem is identified—either the dentist diagnoses the issue during a routine exam, or the patient identifies the problem and calls for an appointment. This appointment is called the initial consultation. During an initial consultation, the dentist examines the patient and determines the cause and extent of the problem. The dentist will recommend a crown if a tooth is damaged, fractured or decayed beyond repair. Or, she’ll prescribe a bridge when a tooth needs to be extracted or has already been removed. 0204551LB05B-27-74 27-23 Dental Assistant The dentist must determine extent of a problem The dentist will often have you take a few radiographs to check the pulp vitality and the supporting bone of the tooth receiving the crown. If the tooth has extensive decay or if there is a risk of infection or injury to the tooth’s pulp, a root canal treatment may be necessary before proceeding. Once the dentist decides on the appropriate treatment, the procedures to make and fit a crown or bridge are very similar. Both involve these basic steps: 1. Prepare the tooth. 2. Build up the tooth with retention materials. 3. Take the final impression. 4. Fabricate and place provisional coverage. 5. Prepare the lab script and send the impression to the lab. 6. Deliver the crown or bridge, fit the crown or bridge and cement it. These procedures typically occur in two visits to the dentist’s office as follows: First Visit 1. The dentist prepares the tooth or teeth for the appropriate prosthodontic device by reducing its height and contour. 2. The dentist builds up the core, if necessary, to make sure there is adequate structure to receive the prosthesis. 3. The dental assistant helps with taking a final impression. 4. The dental assistant makes and places a temporary prosthesis. 5. The dentist sends the impression and prescription to the dental laboratory to fabricate the prosthesis. Second Visit 1. The dentist removes the temporary prosthesis. 2. The dentist adjusts the delivered permanent crown or bridge (if necessary), seats the crown or bridge and cements it in place. 27-24 0204551LB05B-27-74 Prosthodontics Procedure: Cast Crown A common procedure you’ll assist with is placing a cast crown. Let’s look at the various steps in that process. Prepare the Tooth for the Crown On the first visit, a lot happens. You’ll get things rolling by setting up the room before the patient arrives. The dentist gives specific instructions about what’s needed, but the necessary equipment and supplies generally includes: Local anesthetic setup Alginate impression setup Shade guide Large spoon excavator Gingival retraction setup Cotton rolls and gauze sponges High-volume oral evacuator (HVE) tip Occlusal registration setup High-speed handpiece with burs, diamond stones and discs Dentist’s choice of hand instruments Next, the dentist begins the tooth preparation process, which involves a number of steps: A shade guide matches the exact color of teeth. 1. The dentist first anesthetizes the tooth and the surrounding tissues. While waiting for the anesthetic to take effect, the dentist uses the shade guide to select the exact color of porcelain that matches the patient’s natural tooth color. The shade guide contains samples of all available shades, identified by numbers. The dentist moistens the color sample so it will more accurately match a moistened tooth, and then he holds it next to the tooth being treated, in natural light. The dental assistant notes the number of the matching sample on the patient record and the laboratory prescription. 0204551LB05B-27-74 27-25 Dental Assistant 2. Next, the dentist removes all decay or fractured portions of the tooth using a high-speed handpiece fitted with diamond stones. Then the dentist reduces the tooth to make room for the crown. To do this, he will file down the occlusal surface and proximal sides with the high-speed handpiece and various burs. The amount of tooth the dentist removes depends on the type of crown he will use. For example, all- metal crowns are thinner and require less tooth structure removal than all-porcelain or porcelain-fused- to-metal ones. Generally, the dentist removes about one to two millimeters of tooth structure (in addition to any damaged portion). 3. The reduction process leaves a thimble-shaped “miniature” tooth that will receive the crown. The prepared tooth must allow the cast restoration to slide into place and withstand the forces of occlusion. Likewise, the gingival margins of the preparation must provide a smooth, strong junction between the edges (margins) of the cast restoration and the surface of the tooth. Build up the Core with Retention Aids When a large area of the tooth is missing due to decay or damage, the dentist must use restoration material to build up the tooth to support the crown. Build-ups are done most often when the coronal portion of a tooth is fractured, badly decayed or has been treated endodontically. A buildup restores tooth structure and ensures there is no decay present prior to placing the crown. In these situations, the dentist can use two types of support: a core buildup or a post. The dentist uses a core buildup when a tooth has vital pulp. A core buildup uses restorative material to support the cast crown by providing a larger surface area for cementing the crown. If an amalgam restoration is already in place, the dentist shapes and prepares the restoration as the core. If a restoration is NOT in place, the dentist uses a reinforced glass ionomer cement or a self-curing or light-cured composite material to create the core buildup with an anatomic crown form. The material is put in the crown form and placed on the tooth. After the filler initially sets, the dentist removes and peels away the crown form. The final set takes about ten more minutes. Then the dentist reduces the material, just as if it were the natural tooth, to provide the foundation of the crown preparation. The dentist uses a post when a tooth no longer has vital pulp. He places a post in the root canal to serve as a support for the crown. The dentist uses a preformed post of titanium or titanium alloy if it fits accurately. However, if it does not fit, the dentist must use a cast post. A dental laboratory technician fabricates the cast post from an acrylic pattern. The cast post is usually made of gold, titanium or some other metal. The post is placed deep in the canal with a portion of it extending to the height of the core build-up. Once the post is cemented in place, the dentist uses a core build-up to support the crown. Take Final Impression After reshaping (preparing) the tooth, the dentist uses an impression tray with impression material to make an impression of the tooth that will receive the crown. The dental laboratory needs this final impression (also referred to as the master impression) to make the custom crown. 27-26 0204551LB05B-27-74 Prosthodontics A final impression must include a detailed preparation that extends gingivally beyond the prepared tooth. To accomplish this, the dentist must use gingival retraction, which takes place after the tooth preparation is complete and just before the final impression is taken. Packing the cord into the sulcus Gingival retraction is essential for making a good impression. Let’s learn the procedure to place and remove gingival retraction cord. Virtual Lab: Place Retraction Cord To view this Virtual Lab, go to the Student Site and select Resources. At this time, you will select Place Retraction Cord to watch the instructional video. Review this procedure and watch the Virtual Lab until you can explain the procedure without reading the steps or watching the lab. Equipment Needed: Basic setup (mouth mirror, double ended explorer, cotton pliers), perio- probe, air-water syringe tips, cotton rolls, cotton 2 × 2 gauze, floss, HVE tip, cord packing instrument, retraction cord (one extra fine size and one large size, cut to size needed to go around the circumference of the prepped tooth into the sulcus), hemostatic agent (one or two drops on mixing pad and cords will absorb agent), wax wafer 1. The dental assistant should use proper hand hygiene and wear proper PPE—exam gloves, mask, protective eyewear and long-sleeved protective gown. 2. Make sure that appropriate barriers are in place. 3. After the dentist has prepared the tooth for the new crown or bridge placement, pack a retraction cord between the tooth and the sulcus. 4. Using cotton pliers, deliver the thin retraction cord to the prep site. 5. Pack the cord using the cord packing instrument with firm pressure making sure the cord is placed below the prepped margin and the ends are secured within the sulcus. 6. Rinse with water to remove excess hemostatic agent. 7. Using cotton pliers, deliver the thicker cord to the prepped site on top of the finer cord. 8. Using the cord packing instrument, firmly pack the thick retraction cord on top of the fine cord, making sure the margins of the prepped tooth are visible. This will ensure an accurate final impression. 9. Make sure the ends are tucked into the sulcus. 10. The dentist may refine the margins of the prep once the tissue has been retracted. He will check the clearance with a wax wafer to be sure the prep has adequate clearance against the opposing tooth. 0204551LB05B-27-74 27-27 Dental Assistant 11. Provide moisture control with proper placement of the HVE. 12. The second, thicker cord will be removed prior to taking the final impression. 13. The finer cord stays in the sulcus area to keep the tissue retracted during the final impression. This will keep the margins clear and allow the dental lab to make the most accurate permanent crown. 14. You will remove the finer cord prior to cementing the provisional crown. Fabricate and Place Provisional Coverage Temporization is the process to make and place provisional coverage. A temporary crown is fabricated in the office and temporarily cemented to protect the prepared teeth while the laboratory makes the permanent crown. Many dentists use a well-trained assistant to fabricate the temporary following the final impression. This frees up the dentist to move on to a different patient. The dental assistant can then fabricate the temporary without as much time pressure as there would be if another patient had to move into that chair immediately. The dentist determines what type of temporary to use—a custom acrylic crown, a preformed polymer crown, aluminum crown or preformed polycarbonate crown. The decision is based on the patient’s needs; however, most dentists decide based purely on their preference. The custom acrylic temporary crown is the most commonly used provisional, although it is the most time- consuming to make. It is suitable for any tooth, anterior or posterior. The dental assistant uses the alginate impression she created earlier and fills the appropriate tooth position in the impression with acrylic material. She then puts the acrylic loaded impression back in the patient’s mouth, lets it set for about three minutes and then carefully removes it from the mouth. She can then remove the temporary crown from the impression and place it on the patient’s tooth preparation to cure. She then trims it, fits it, checks occlusion and finally polishes it. Virtual Lab: Place a Provisional Crown To view this Virtual Lab, go to the Student Site and select Resources. At this time, you will select Place a Provisional Crown to watch the instructional video. Review this procedure and watch the Virtual Lab until you can explain the procedure without reading the steps or watching the lab. Equipment Needed: Basic setup (mouth mirror, double ended explorer, cotton pliers), perio probe, air-water syringe tips, cotton rolls, cotton 2 × 2 gauze, floss, HVE tip, Dri-Angles, plastic instrument, bite registration elastomeric impression using triple tray taken before the tooth is prepared, provisional crown/bridge material, three-quarter arch triple tray, light-bodied and heavy-bodied elastomeric impression material, straight handpiece with acrylic bur and polishers, high-speed handpiece with crown prep bur block, articulating paper and holder, temporary cement 1. The dental assistant should use proper hand hygiene and wear proper PPE—exam gloves, mask, protective eyewear and long-sleeved protective gown. 2. Make sure that appropriate barriers are in place. 3. At this point, the patient has been seated and is wearing protective glasses and a patient napkin. 4. Load a triple tray with elastomeric impression material. 5. Place this in the patient’s mouth to take a preliminary impression of the arch before the dentist prepares the tooth. 27-28 0204551LB05B-27-74 Prosthodontics 6. Check the impression to be sure it is adequate. 7. The dentist will then prepare the tooth to receive a permanent crown at a later date. 8. Use proper HVE technique to provide moisture control. 9. The dentist will extrude the light-bodied elastomeric impression material around the preparation and into the prepared sulcus, which is retracted with retraction cord. 10. Load the heavy-bodied elastomeric impression material into the triple tray. Place the tray into the patient’s mouth for approximately five minutes. Tell the patient to bite together in natural occlusion (“your normal bite”). 11. Remove the impression from the patient’s mouth and the dentist will inspect it. 12. Disinfect the impression before sending it the lab. 13. Using the initial provisional crown impression tray, fill the area of the prepped tooth with the crown/bridge provisional material. 14. Place the provisional impression back into the patient’s mouth and seat it around the prepped tooth for approximately one minute. 15. After removing the provisional impression, let it cure for approximately three to four minutes. 16. Rinse the patient’s mouth and look for loose acrylic material. 17. Check the provisional crown in the impression using a plastic instrument to be sure it is set up. 18. With an acrylic bur, trim away flash from the provisional crown. 19. Using an air-water syringe, clear any acrylic dust from the crown. 20. Try the provisional crown on the prepped tooth for fit and adjust accordingly. Bore out the inside if needed. 21. Check the patient’s occlusion with articulating paper and adjust the crown as needed to create proper occlusion. 22. Using an explorer, check the margins to be sure the crown is completely seated. 23. Once the crown is completely adjusted, polish the provisional crown using a polishing bur. 24. Rinse and dry the prep. 25. Place a small amount of temporary cement into the provisional crown. 26. Place the crown firmly onto the prepped tooth with finger pressure. 27. To fully seat the crown, ask the patient to bite down on a cotton roll with firm pressure and let it set up for 30 to 60 seconds. 28. Use an explorer and mouth mirror to carefully remove excess cement around the margins. 29. You can also use the HVE to vacuum cement that you can’t easily retrieve with the hand instruments. 30. Check the contact area with floss. Be sure to pull the floss out from the side of the tooth so you don’t accidently pull the crown off. 31. Give the patient a final rinse and use a cotton roll to remove any remaining marks from the articulating paper. 32. Provide the patient with these home care instructions. Call the office if the provisional crown is not comfortable. Avoid sticky foods such as caramels. Brush normally. When flossing around the crown, pull dental floss out from the side of the tooth so you won’t loosen or remove the provisional crown. The gum tissue may be sore for a day or two. Rinse the area with warm salt water if needed. 33. Dismiss the patient to schedule her next appointment. When the permanent crown is delivered, the dentist will remove the provisional crown and seat the permanent crown. 34. Remove PPE and wipe hands with an alcohol-based handrub. 35. Document the procedure. 0204551LB05B-27-74 27-29 Dental Assistant Prepare the Lab Script It’s important that a cast restoration fit the prepared tooth exactly. Otherwise, the prosthesis will be uncomfortable for the patient or will become detached after it is placed. To accomplish this precision, the dental laboratory technician carefully fabricates the prosthesis based on the dentist’s specific requirements as stated in the laboratory prescription (“lab script”) to fabricate the cast. A laboratory prescription is like a recipe, describing the restoration in detail and giving the lab tech precise instructions about the construction of the restoration. As a dental assistant, you can fill out the prescription and ask the dentist to review the information before he signs it. One copy of the prescription goes with the case (the materials that the lab needs to construct the prosthesis) to a reputable dental laboratory and the other remains with the patient’s records in the dental office. A laboratory prescription contains this information: Dentist’s name License number Address and phone number Signature Patient identification (either name or case number) Type of prosthesis requested Type of material to be used Exact shade of restoration Anatomical characterization, if needed Due date when case is expected back at dental office, also known as the seat date After the dentist writes the lab script and sends it to the laboratory, the lab technician constructs the crown based on the impression and the dentist’s prescription. Meanwhile, you’ll make a second appointment for the patient. The date of the appointment is based on the number of days the laboratory needs to complete the crown. Before the patient’s next appointment, you’ll need to make sure the laboratory has returned the completed crown. If not, you’ll need to reschedule the patient’s appointment. 27-30

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