(Test Bank) Dental Materials

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Test Bank

3rd Edition

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Test Bank for Dental Materials, The downloadable file consists of 180 pages, and the total size of the file is 1.93 MB. Purchase now only for highly discounted price.

Author(s): Hatrick

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Chapter 01: Introduction to Dental Materials MULTIPLE CHOICE 1.Until 1970, which of the following groups of dental auxiliaries were allowed to perform intraoral functions in all states? 1. Dental hygienists 2. Registered dental assistants 3. Certified dental assistants 4. On-the-job trained dental assistants a.1, 2, 3, 4 b.1, 2, 3 c.1, 2 d.1 ANS:D Until 1970, only the dental hygienist was allowed to perform intraoral functions in all states. Although laws vary from state to state, virtually every state has modified, updated, and made changes to state restrictions to allow for the performance of intraoral procedures by all allied oral health care practitioners. REF:p. 1TOP:The Role of the Dental Auxiliary in the Use of Dental Materials 2.Silver paste was first mentioned as a restorative material for teeth by the: a.Chinese. b.Greeks. c.Romans. d.French. ANS:A Silver paste was first mentioned as a restorative material for teeth by the Chinese in 659 AD. More than 1000 years later, in 1800, it was produced in France from “shavings from silver cut from coins mixed with enough mercury to form a sloppy paste.” Health problems arising from the high mercury content of this early amalgam prompted the American Society of Dental Surgeons to pass a resolution in 1846 stating that amalgam should not be used under any circumstances. REF:p. 3TOP:The Historical Development of Dental Materials 3.What was the “Amalgam War” fought over? a.Mining rights in states in the Western region of the United States b.The price of silver in relation to tin and zinc c.The value and safety of silver dental amalgam d.Patent issues between France and England ANS:C The “Amalgam War” was fought over the value and safety of silver dental amalgam. It did not end until 1895, when G.V . Black developed an acceptable amalgam formula. REF:p. 3TOP:The Historical Development of Dental Materials4.Which of the following restorative techniques was first introduced in 1955? a.Cast gold inlays b.Cohesive gold foil c.Acid-etch technique d.Synthetic resins for denture bases ANS:C The acid-etch technique was introduced in 1955. Cohesive gold foil, which could be condensed directly into the cavity preparation, was introduced in 1855. In 1907, Dr. William Taggart demonstrated a casting method to produce gold inlays. Synthetic resins were introduced in 1932; these resins soon replaced rubber as the denture base of choice. Around this time, synthetic resins also became a popular tooth-colored alternative, and, together with the introduction of the acid-etch technique, they have evolved into composite resin, one of the most popular restorative materials. REF:p. 3TOP:The Historical Development of Dental Materials 5.What is Dr. Frederick McKay credited with? a.Developing an acceptable formula for silver dental amalgam b.Noting dental fluorosis in Colorado Springs c.Demonstrating a casting method to produce gold inlays d.The introduction of dental cements ANS:B Dr. Frederick McKay is credited with noting dental fluorosis in Colorado Springs in 1901. Together with G.V . Black, he determined that drinking water was the factor. These caries-free but mottled teeth prompted Dr. McKay to suggest changes in the water supply, leading to the first community water fluoridation programs in 1945. REF:p. 3TOP:The Historical Development of Dental Materials 6.Since 2005, the American Dental Association (ADA) Seal of Acceptance is awarded to _____ products. a.both professional and consumer b.professional but not consumer c.consumer but not professional d.neither professional nor consumer ANS:C Since 2005, the American Dental Association (ADA) Seal of Acceptance is awarded to consumer but not professional products. Although strictly a voluntary program, more than 1300 consumer dental products carry the Seal of Acceptance. Most common among these are toothpaste, toothbrushes, mouth rinses, floss and other interdental cleaners, sugar-free chewing gum, and denture adherents and cleansers. REF:p. 4TOP:The Agencies Responsible for Standards (American Dental Association) 7.Dental materials considered devices, as well as over-the-counter products sold to the public, are subject to control and regulation of the _____ Center for Devices and Radiological Health. a.Food and Drug Administrationb.Drug Enforcement Administration c.Centers for Disease Control and Prevention d.Department of Human and Health Services ANS:B Dental materials considered devices, as well as over-the-counter products sold to the public, are subject to control and regulation of the Food and Drug Administration Center for Devices and Radiological Health. The original Food and Drug Act of 1906 did not include provisions to ensure medical and dental device safety or claims. In 1976, the Medical Device Amendment was signed to give the Food and Drug Administration regulatory authority over medical and dental devices, which are now classified and regulated according to their degree of risk to the public. REF:p. 5 TOP:The Agencies Responsible for Standards (U.S. Food and Drug Administration) 8.Which of the following represents the standards used to develop specifications and testing on an international level? a.World Health Organization (WHO) b.Food and Drug Administration (FDA) c.American Dental Association (ADA) d.International Standards Organization (ISO) ANS:D The International Dental Federation and the International Standards Organization (ISO) represent the standards used to develop specifications and testing on an international level. These standards are developed through the ISO’s technical committee for dentistry (ISO TC 106). REF:p. 5TOP:The Agencies Responsible for Standards (International Agencies) 9.Which of the following statements is true concerning the American Dental Association (ADA) Seal? a.All dental products qualify for the Seal. b.It helps consumers make informed decisions about the safety and efficiency of products. c.The ADA Seal is usually awarded for the life of the product. d.Once a product has been accepted, it does not need to be reevaluated if its composition changes. ANS:B Consumers and dentists rely on the ADA Seal to assist them in making informed decisions regarding a product’s safety and efficiency. Not all dental products qualify for the Seal. The ADA Seal is usually awarded for a period of 5 years, at which time the product is reevaluated. Products that have been previously accepted are also reevaluated anytime their composition changes. REF:p. 5TOP:The Agencies Responsible for Standards (American Dental Association) 10.Who does the delivery of dental materials most often fall to? a.The dentistb.The dental hygienist c.The dental assistant d.The dental laboratory technician ANS:C The dental assistant is most directly responsible for the delivery of dental materials within specific guidelines outlined by the dental manufacturer. REF:p. 1TOP:The Role of the Dental Auxiliary in the Use of Dental Materials 11.Which of the following is not a classification of dental materials? a.Preventive b.Biological c.Restorative d.Therapeutic ANS:B Dental materials are classified as preventive, restorative, and therapeutic materials. REF:p. 2TOP:The Role of the Dental Auxiliary in the Use of Dental Materials 12.What is the best resource for choosing which dental material to use? a.Reading professional journals b.Meeting with manufacturers’ representatives c.Discussing which materials colleagues use d.All of the above are good resources. ANS:D Professional journals, dental materials manufacturers and manufacturers’ representatives, Internet links, and other resources can provide invaluable information. REF:p. 2TOP:The Role of the Dental Auxiliary in the Use of Dental Materials 13.The first acceptable amalgam formula was developed by _____ in 1895. a.G.V . Black b.Pierre Fuchard c.Dr. Frederick McKay d.Dr. William Taggart ANS:A The “Amalgam War” ended in 1895, when G.V . Black developed an acceptable amalgam formula. REF:p. 3TOP:The Historical Development of Dental Materials 14.What is today’s approach to dental care referred to as? a.Individualized care b.Comprehensive care c.Science-based dentistry d.Evidence-based dentistry ANS:BThe ADA defines evidence-based dentistry as an approach to oral health care that requires the judicious integration of systematic assessments of clinically relevant scientific evidence related to the patient’s oral medical history with the dentist’s clinical expertise and the patient’s treatment needs and preferences. REF:p. 2TOP:Evidence-Based Dentistry 15.In history, the earliest recorded mention of restorative dentistry occurs when? a.2500 BC b.600 BC c.1200 AD d.1700 AD ANS:B Much is found in the literature about treatment options, including remedies of potions and prayer, but no evidence of restorative dentistry exists until around 600 BC to 300 BC. REF:p. 2TOP:The Historical Development of Dental Materials 16.According to the earliest historical mention, in which location was fluoride first used? a.China b.Prussia c.England d.Colorado Springs ANS:C Preventive dentistry had an early beginning, with fluoride first introduced in 1874 and dispensed in England at that time for the prevention of caries. REF:p. 3TOP:The Historical Development of Dental Materials MATCHING Match the items with the correct description below. a.Food and Drug Administration b.American Dental Association c.International Standards Organization 1.Seal of Acceptance 2.Regulation over dental devices 3.Standards to develop specifications on an international level 1.ANS:BREF:p. 4 TOP:The Agencies Responsible for Standards (American Dental Association) 2.ANS:AREF:p. 5 TOP:The Agencies Responsible for Standards (U.S. Food and Drug Administration) 3.ANS:CREF:p. 5 TOP:The Agencies Responsible for Standards (International Agencies) SHORT ANSWER1.What would be the four characteristics of the perfect dental material? ANS: The perfect dental material would be biocompatible, bond permanently to tooth structure, be esthetic with the tooth/tissue structures, and repair or regenerate missing tissues. REF:p. 2TOP:The Role of the Dental Auxiliary in the Use of Dental MaterialsChapter 02: Oral Environment and Patient Considerations MULTIPLE CHOICE 1.Some dental materials may be therapeutic in small quantities or if in contact with tissues for a short period of time. Dental materials may be irritating or toxic with longer or larger doses. a.Both statements are true. b.Both statements are false. c.The first statement is true, and the second statement is false. d.The first statement is false, and the second statement is true. ANS:A Some dental materials may be therapeutic in small quantities or if in contact with tissues for a short period of time but also may be irritating or toxic with longer or larger doses. Topical fluoride is of great benefit when used according to manufacturers’ directions but can be irritating to soft tissues and can even excessively etch enamel if used improperly. REF:p. 9TOP:Biocompatibility 2.Normal masticatory forces on the occlusal surfaces of molar teeth can increase to as much as _____ pounds per square inch on a cusp tip. a.280 b.1000 c.10,000 d.28,000 ANS:D Normal masticatory forces on the occlusal surfaces of molar teeth can increase to as much as 28,000 pounds per square inch on a cusp tip. Normal masticatory forces on the occlusal surfaces of molar teeth average 90 to 200 pounds. Masticatory forces decrease in incisor areas and can increase during bruxing or clenching. REF:p. 10TOP:Force and Stress 3._____ force is applied when two surfaces slide against each other in opposite directions. a.Compressive b.Shearing c.Tensile d.Axial ANS:B Shearing force is applied when two surfaces slide against each other or in a twisting or rotating motion. An incisor used for cutting is an example of shearing forces. REF:p. 10TOP:Force and Stress 4.Stress is the amount of force exerted from within an object, and _____ is the amount of change that the force has produced. a.strain b.tensionc.compression d.chemical bonding ANS:C Stress is the amount of force exerted from within an object, and strain is the amount of change that the force has produced. The normal process of chewing rarely involves only one type of stress; these combinations of stresses form complex stress combinations. REF:p. 11TOP:Force and Stress 5.Which of the following materials has the highest ultimate compressive strength (lbs/in2)? a.Acrylic b.Porcelain c.Amalgam d.Composite resins ANS:C Amalgam has the highest ultimate compressive strength (45,000 to 64,000 lbs/in2), followed by composite resins (30,000 to 60,000 lbs/in2), porcelain (21,000 lbs/in2), and acrylic (11,000 lbs/in2). Amalgam and composite resins more closely replicate enamel in compressive strength, but porcelain falls short. Porcelain is more likely to fracture under compressive stresses. REF:p. 11 TOP:Table 2-1: Ultimate Compressive and Tensile Strengths of Tooth and Restorative Structures 6.Which of the following statements is correct about fatigue failure? a.It is not a factor for restorative dental materials. b.It is not dependent on conditions in the oral cavity. c.It occurs as the result of a large, single-force application. d.It occurs as the result of microscopic flaws that grow over time. ANS:B Fatigue failure occurs as the result of microscopic flaws that grow over time. Failures rarely occur in a single-force application; rather, they occur when stress is frequently repeated. A metal wire will eventually break when bent repeatedly. Restorative materials are subject to repeated fatigue testing for all forces. Conditions of the oral cavity such as humidity and temperature and pH fluctuations may also increase fatigue failure. REF:p. 11TOP:Force and Stress 7.The normal resting pH of saliva ranges from 6.2 to _____, which is neutral. a.1 b.6.6 c.7 d.14 ANS:C The normal resting pH of saliva ranges from 6.2 to 7, which is neutral. It can fluctuate higher or lower by several points during the course of a day. Many materials that would be compatible in a neutral environment will not be compatible in an acidic one.REF:p. 11TOP:Moisture and Acid Levels 8.The staining of resins and acrylics from repeated exposure to coffee, tea, and other dyed beverages is due to: a.compressive forces. b.water sorption. c.galvanism. d.tarnish. ANS:B The staining of resins and acrylics from repeated exposure to coffee, tea, and other dyed beverages is due to water sorption. Water sorption is the ability to absorb moisture. Dentures, when placed in a glass of water, will take up the liquid and become slightly larger. Some acrylics will absorb both odors and tastes from foods. REF:p. 11TOP:Moisture and Acid Levels 9.Which of the following dental restorative materials is particularly susceptible to corrosion? a.Acrylic b.Dental porcelain c.Dental amalgam d.Composite resin ANS:C Dental amalgam is particularly susceptible to corrosion, causing marginal breakdown and discoloration of tooth structures. In newer, high-copper amalgams, this may not be as critical to their longevity. REF:pp. 11-12TOP:Moisture and Acid Levels 10.Which of the following has been suggested to delay formation of surface tarnish on dental amalgams? a.Incremental addition b.Polishing c.Use of non–copper-containing dental amalgam d.Undercondensation ANS:B Polishing of amalgams to produce a smooth surface has been recommended to help delay the process of surface tarnish. Surface tarnish, discoloration due to oxidation of the metal’s surface, can accelerate in crevices between a tooth and restoration and on rough surfaces. REF:p. 12TOP:Moisture and Acid Levels 11.Which of the following is true of galvanism? a.It is an electrical current transmitted between two similar metals. b.It is observed in patients with composite resin but not silver amalgam restorations. c.Galvanic stimulation will decrease with time as oxides form on the surface of the metal. d.The salts of the saliva inhibit the movement of electrical current from one type of metal to another.ANS:C Galvanic stimulation will decrease with time as oxides form on the surface of the metal. Galvanism is an electrical current transmitted between two dissimilar metals. An environment containing moisture, acidity, and dissimilar metals makes the generation of electrical current possible. The salts of the saliva facilitate the movement of electrical current from one type of metal to another. The current may result in stimulation to the pulp, called galvanic shock. REF:p. 12TOP:Galvanism 12.What could excessive expansion of a restorative material result in? a.Corrosion b.Galvanism c.Fracture of cusps d.Leakage of fluid and bacteria into the gaps ANS:C Excessive expansion of a restorative material may result in fracture of cusps. Excessive contraction may result in leakage of fluid and bacteria into the open gaps, resulting in sensitivity. Expansion and contraction are measured using the coefficient of thermal expansion, the measurement of change in volume or length in relationship to change in temperature. REF:p. 12TOP:Temperature 13.What is percolation? a.The rate at which heat flows through a material b.A form of chemical rather than mechanical retention c.Something that helps seal the interface between tooth and restorative material d.Something that allows the ingress of bacteria and oral fluids and may lead to recurrent caries, staining, and pulpal irritation ANS:D Percolation allows the ingress of bacteria and oral fluids and may lead to recurrent caries, staining, and pulpal irritation. Percolation is the repeated shrinkage and expansion of the restoration during ingestion of cold and hot fluids, producing the opening and closing of a gap between the restoration and the tooth surface. REF:p. 12TOP:Temperature 14.Which of the following is the best thermal conductor? a.Gold b.Dentin c.Enamel d.Ceramic ANS:A Gold is one of the best thermal conductors; nonmetals such as ceramics, resins, cements, enamel, and dentin are poor conductors. Poor conductors can be used as insulators; dentin is a natural insulator. REF:p. 12TOP:Temperature15.Which of the following restorative materials has a coefficient of thermal expansion and thermal conductivity closest to enamel? a.Gold b.Amalgam c.Porcelain d.Composite resin ANS:C Porcelain has a coefficient of thermal expansion ( 10–6/°C) of 15 and thermal conductivity (k) ([mcalcm]/cm sec/°C) of 2.50; enamel has a coefficient of thermal expansion of 11 and thermal conductivity of 2.0. In contrast, the coefficient of thermal expansion of amalgam is 20 to 28, and the thermal conductivity of amalgam is 54, but the coefficient of thermal expansion of composite resin is 26 to 40, and the thermal conductivity of composite resin is 2.60. REF:p. 13TOP:Table 2-2: Thermal Properties of Tooth and Restorative Structures 16.The technique of chemical bonding rather than mechanical means to produce retention requires _____ removal of tooth structure and produces a _____ retentive force between tooth and restoration. a.more; stronger b.more; weaker c.less; stronger d.less; weaker ANS:C The technique of chemical bonding rather than mechanical means to produce retention requires less removal of tooth structure and produces a stronger retentive force between tooth and restoration. Additionally, it can seal the margin of the restoration to prevent seepage of bacteria and fluids through percolation. REF:p. 13TOP:Retention 17.Which of the following statements is true for the property of wetting as related to dental materials? a.The Teflon surface of cooking equipment has good wetting. b.A thin film of dental cement is desirable to cement crowns. c.Liquids generally spread better over low surface energy surfaces. d.A surface has high surface energy when liquids bead up on the surface. ANS:B A thin film of dental cement is desirable to cement crowns. This allows the cement to completely wet the surfaces and for excess material to flow from under the crown when it is seated under pressure during cementation. The Teflon surface of cooking equipment has poor wetting. The surface has low surface energy such as on wax or many plastics when liquids bead up on the surface. Liquids generally wet or spread over high surface energy surfaces better; metals, ceramics, and enamel have high surface energies. REF:p. 14TOP:Retention 18.Microleakage into the interface between tooth structure and restorative material is responsible for much of the _____ observed following tooth restoration.1. recurrent decay 2. marginal staining 3. postoperative sensitivity 4. tarnish a.1, 2, 3, 4 b.1, 2, 3 c.2, 3, 4 d.1, 2 ANS:B Microleakage into the interface between tooth structure and restorative material is responsible for much of the recurrent decay, marginal staining, and postoperative sensitivity observed following tooth restoration. REF:p. 14TOP:Microleakage 19._____ refers to the intensity or strength of the color. a.Hue b.Value c.Chroma d.Opacity ANS:C Chroma refers to the intensity or strength of the color. Hue is the dominant color of the wavelength detected. Value describes how light or dark the color is. If light is completely absorbed by the object, it is opaque. REF:p. 14TOP:Esthetics 20.Which of the following is considered to be the most reliable means of clinical assessment of composite and glass ionomer restorations? a.The patient history b.Evaluation of radiographs c.Use of the air-water syringe d.Tactile evaluation of the tooth surface ANS:D Tactile evaluation of the tooth surface is considered to be the most reliable means of clinical assessment of composite and glass ionomer restorations. Some composite and glass ionomer restorations may have a rougher surface than enamel. Tracing the enamel surface onto the restoration with the sharp tip of an explorer is the best way to distinguish this difference. The clinician will detect a smooth surface on the enamel and a “scratchy” surface on the restoration. REF:pp. 15-16TOP:Detection of Restorative Materials 21.Which of the following would not be an adverse effect of a material? a.Toxicity b.Hyposensitivity c.Hypersensitivity d.Postoperative sensitivityANS:B Adverse responses may include postoperative sensitivity, toxicity, and hypersensitivity. REF:p. 9TOP:Biocompatibility 22.Of the three types of forces, which is most concerned with the stretching of a material? a.Tensile force b.Compressive force c.Shearing force ANS:A Tensile force is applied in the opposite direction as it pulls or stretches an object. REF:p. 10TOP:Force and Stress 23.When an object cannot resist force, _____ occurs. a.deformation b.distortion c.deformation and distortion ANS:C If the stress within an object cannot resist the force, distortion or deformation occurs. REF:p. 11TOP:Force and Stress 24.Torque is a combination of which forces? a.Compressive and tensile b.Compressive and torsion c.Shearing and tensile d.Shearing and compressive ANS:A Torque, a.k.a. torsion, is a combination of compressive and tensile forces. REF:p. 10TOP:Force and Stress 25.Which material listed would show the lowest level of solubility? a.Amalgam b.Composite resin c.Porcelain d.Cement ANS:C Porcelain and high noble metals have low solubility. Other restorative materials such as amalgam, composite resin, and cement have varying levels of solubility depending on the properties of each material. REF:p. 11TOP:Moisture and Acid Levels 26.Most modern dental materials are made to be moisture resistant. a.True b.FalseANS:B Most materials react adversely to moisture either during placement or over time. REF:p. 11TOP:Moisture and Acid Levels 27.Contact between two dissimilar metals in the mouth may result in what reaction? a.Galvanic shock b.Metallic taste c.Electrical current d.All of the above are possible. ANS:D An environment containing moisture, acidity, and dissimilar metals makes the generation of electrical current possible. This is known as galvanism. The current may result in stimulation of the pulp, called galvanic shock. It may also create a metallic taste in the mouth. REF:p. 12TOP:Galvanism 28.Why is the coefficient of thermal expansion significant in dental materials? a.It measures the change in volume and length of a restoration. b.It measures the amount of percolation of the restoration interface. c.It measures the change in oral temperature related to foods ingested. d.It measures the amount of stress and strain placed on the restoration. ANS:A Expansion and contraction are measured using the coefficient of thermal expansion (CTE). This measures the change in volume or length in relationship to the change in temperature. REF:p. 12TOP:Temperature 29.Which of the following is not a good conductor of temperature? a.Gold crown b.Amalgam restoration c.Composite resin restoration ANS:C Metals, such as gold and amalgam, are good conductors of temperature, but nonmetals are poor conductors of temperature. REF:p. 12TOP:Temperature 30.Some materials give off heat when mixed. What is this called? a.Chemical reaction b.Exothermic reaction c.Thermal conductivity d.Coefficient of thermal expansion ANS:B Some materials when mixed will produce heat. This exothermic reaction must be minimized to protect the tooth structures from excess heat, thus causing sensitivity or pulpal damage. REF:p. 13TOP:Temperature31.What causes microleakage? a.A poorly placed restoration b.A fracture within a restoration c.Expansion and contraction of a restoration d.All of the above could cause microleakage. ANS:D The space between the walls of the preparation and the preparation is called the interface. If the interface is not sealed, fluids and microorganisms can penetrate between the tooth surface and the restorative material. This seepage of harmful materials, or microleakage, results in tooth sensitivity, recurrent decay, and marginal staining. REF:p. 14TOP:Microleakage 32.Which term describes the thicker or thinner a material is? a.Density b.Viscosity c.Flowability d.Thixotropic ANS:D Viscosity is a material’s ability to flow. The thicker the material, the harder it is to flow. REF:p. 13TOP:Retention 33.Adhesion is the method of _____ retention. a.chemical b.mechanical c.dual ANS:A Retention may be mechanical, chemical through adhesion, or a combination of the two. REF:p. 13TOP:Retention 34.The color range of a tooth is usually seen by the human eye as yellow or brown. What is this component classified as? a.Hue b.Value c.Chroma ANS:A The three components of color result in hue, chroma, and value. Hue is the dominant color of the wavelength detected. Teeth are predominately seen in the yellow and brown ranges. Chroma is the intensity or strength of the color. Value describes how light or dark the color is. REF:p. 14TOP:Esthetics 35.Which of the following is not a concern regarding identification of dental materials in the mouth? a.Therapeutic agents could erode some materials.b.Scaling could damage the surfaces of some materials. c.Both are concerns when materials are identified. ANS:C It is important that oral health care professionals are able to identify restorative materials within the oral environment, to treat them appropriately. Heavy pressure during scaling, the use of sonic and ultrasonic scaling or air polishing, and inappropriate use of polishing agents may gouge or scratch the surface of a restoration. REF:p. 15TOP:Detection of Restorative Materials 36.What is the thermal conductivity of composite resin? a.Similar to tooth structure b.Lower than tooth structure c.Similar to metal restorations d.Does not conduct temperature ANS:A Thermal conductivity is the rate at which heat flows through a material. Metals are particularly excellent conductors. Gold is one of the best thermal conductors, but non-metals such as ceramics, resins, cements, enamel, and dentin are poor conductors. REF:p. 12TOP:Temperature MATCHING Match the items with the correct description below. a.Electrical current between two dissimilar metals b.Discoloration due to oxidation of the metal’s surface c.Deterioration of the metal due to moisture and acid present in the oral d.The rate at which heat flows through a material e.Opening and closing of a gap between the restoration and the tooth surface 1.Corrosion 2.Tarnish 3.Galvanism environment 4.Thermal conductivity 5.Percolation 1.ANS:CREF:p. 11TOP:Moisture and Acid Levels 2.ANS:BREF:p. 12TOP:Moisture and Acid Levels 3.ANS:AREF:p. 12TOP:Galvanism 4.ANS:DREF:p. 12TOP:Temperature 5.ANS:EREF:p. 12TOP:Temperature SHORT ANSWER 1.List and describe the three basic types of force. ANS:•Compressive force. Force applied to compress an object. Posterior teeth are ideally suited for this type of force. The large occlusal surface and the multirooted base will resist a crushing force. •Tensile force. Force applied in opposite directions to stretch and object. When biting forces are used to stretch a material, the tooth is exerting tensile forces. •Shearing force. Force applied when two surfaces slide against each other or in a twisting or rotating motion. An incisor used for cutting is an example of shearing forces. REF:p. 10TOP:Force and Stress 2.List and describe the three components of color. ANS: •Hue: The dominant color of the wavelength reflected •Value: How light or dark the color is •Chroma: The intensity or strength of the color REF:p. 14TOP:EstheticsChapter 03: Physical and Mechanical Properties of Dental Materials MULTIPLE CHOICE 1.Which type of bond occurs when two atoms share electrons in their outer shell, creating full shells for both? a.Ionic bond b.Covalent bond c.Metallic bond d.Hydrogen bond ANS:B Covalent bonds occur when two atoms share electrons in their outer shell, creating full shells for both. Covalent bonds are very strong. Diamond is a good example of a strong covalent bond; it is hard and has a high melting point. REF:p. 20TOP:Physical Structure (Primary Bonds) 2.Which of the following is an example of a secondary rather than primary bond? a.Ionic bond b.Metallic bond c.Covalent bond d.Hydrogen bond ANS:D A hydrogen bond is an example of a secondary bond. Secondary bonds are much weaker than primary bonds. Unlike with primary bonds, no transfer or sharing of electrons occurs. This weakness often leads to deformation or fracture. REF:p. 20TOP:Physical Structure (Secondary Bonds) 3.Which of the following forms of matter has/have both shape and volume? 1. Solid 2. Liquid 3. Gas a.1, 2, 3 b.1, 2 c.2, 3 d.1 ANS:D Solids have the strongest attraction between atoms and molecules and have both shape and volume, a liquid has volume but no shape, and a gas has neither definite shape nor volume. REF:p. 21TOP:Physical Structure (The Three States of Matter) 4.If the molecules of a solid are arranged in a random form with no regular pattern, the solid is called: a.thixotropic. b.amorphous.c.malleable. d.ductile. ANS:B If the molecules of a solid are arranged in a random form with no regular pattern, the solid is called amorphous. The most stable solids have a regular crystalline structure with molecules in a regularly spaced pattern. REF:p. 21TOP:Physical Structure (Solids) 5.Which of the following is the hardest material? a.Enamel of a tooth b.Cementum of a tooth c.Cast gold restorative material d.Composite resin restorative material ANS:A Enamel and porcelain are two of the hardest materials and are more resistant to being scratched than is cementum on the root or composite resins or gold crowns. Hardness is the resistance of a solid to penetration. Hardness is also used to define a material’s resistance to wear and abrasion. The hardness of a material is used to determine the ability of an abrasive to scratch or resist scratching the substrate to which it is applied. REF:pp. 21-22TOP:Physical Structure (Solids) 6.Which of the following statements is true concerning desirable properties of dental materials? a.The maximum amount of stress a material can withstand without breaking is known as the proportional limit. b.Stiffer materials have a high modulus of elasticity. c.Resilience is the ability of a material to resist fracture. d.In most cases, metals tend to be brittle and ceramics tend to be ductile and malleable. ANS:B Stiffer materials have a high modulus of elasticity. The stiffness of a material is its resistance to deformation and is measured by Young’s elastic modulus. The maximum amount of stress a material can withstand without breaking is known as the ultimate strength. Toughness is the ability of a material to resist fracture. In most cases, metals tend to be ductile and malleable and ceramics tend to be brittle. REF:p. 22TOP:Physical Structure (Solids) 7.The higher the viscosity, the greater is a liquid’s ability to resist flow. Usually, the viscosity of liquids increases as the temperature increases. a.Both statements are true. b.Both statements are false. c.The first statement is true; the second statement is false. d.The first statement is false; the second statement is true. ANS:CThe first statement is true, and the second statement is false. The higher the viscosity, the greater is a liquid’s ability to resist flow. Usually, the viscosity of liquids decreases as the temperature increases. Values of viscosity depend on the nature of the fluid; thin fluids have low viscosity, and thicker fluids have high viscosity. REF:p. 23TOP:Physical Structure (Liquids) 8.Which of the following are considered to be therapeutic dental materials? a.Partial and complete dentures b.Fluorides and pit and fissure sealants c.Fillings, inlays, crowns, bridges, and implants d.Medicated bases and topical treatments for periodontal disease ANS:D Medicated bases and topical treatments for periodontal disease are considered to be therapeutic materials used in the treatment of disease. Fluorides and pit and fissure sealants are preventive materials. The classification of restorative materials applies to any filling, inlay, crown, bridge, implant, or partial or complete denture that restores or replaces lost tooth structure, teeth, or oral tissue. REF:p. 23TOP:Application 9.Which of the following is an example of a direct restorative material? a.Porcelain inlay b.Cast gold crown c.Ceramic implant abutment d.Silver dental amalgam restoration ANS:D A silver dental amalgam restoration is an example of a direct restorative material. Some materials, such as amalgams and composites, may be fabricated directly in the mouth. Other materials, because of convenience or toxic or other physically harmful characteristics, need to be fabricated indirectly outside the mouth and then placed into the oral environment. Porcelain, for instance, needs to be fired to temperatures higher than 1000° F, making it necessary to be fabricated indirectly. REF:p. 23TOP:Application 10.Dental plaster begins with _____ components. a.water and powder b.liquid and powder c.paste and liquid d.paste and paste ANS:A Dental plaster begins with water and powder components; composite restorations may use a paste and a blue light as an initiator. Many components are classified as catalyst and base; the catalyst is responsible for the speed at which the reaction occurs and is often the liquid component. REF:p. 23TOP:Composition11._____ time is the time permitted to manipulate the material in the mouth. a.Mixing b.Working c.Initial set d.Final set ANS:B Working time is the time permitted to manipulate the material in the mouth. Mixing time is the amount of time the auxiliary has to bring the components together into a homogenous mix. The initial set time begins when the material can no longer be manipulated in the mouth, and the final set time is when the material has reached its ultimate state. REF:p. 24TOP:Reaction 12.Dual set materials utilize _____ setting reactions. a.both light-activated and chemical b.light-activated but not chemical c.chemical setting but not light-activated d.neither light-activated nor chemical ANS:A Dual set materials utilize both light-activated and chemical setting reactions. Dual set materials begin with the initiation of the blue light source and then continue with the chemical set reaction; this also gives the clinician better control of his or her working time. REF:p. 24TOP:Reaction 13.Which of the following is true concerning initial and final setting times? a.Moisture and pressure controls are frequently important during the initial set. b.The final set always occurs while the patient is still in the dental office. c.The material must not be disturbed through the end of the final set. d.Once a material has reached the initial set, it will not fracture. ANS:A Moisture and pressure controls are frequently important during the initial set. Moisture contamination, from saliva and blood, during initial setting time may have an adverse effect on many dental materials, causing them to fail. Continued firm pressure from biting force or by holding the material firmly in the mouth is essential for materials needing intimate contact with the tooth such as dental cements. The material must not be disturbed through the end of the initial set. The final set may occur while the patient is still in the dental office or several hours later. Appropriate patient postoperative instructions on when and what to eat or on placing pressure on the restoration are essential to avoid fracture of these materials. REF:p. 24TOP:Reaction 14.In general, _____ temperature and _____ humidity will accelerate the reaction of the material. a.high; high b.high; low c.low; high d.low; low ANS:AIn general, high temperature and high humidity will accelerate the reaction of the material, but low temperatures and low humidity will retard the reaction. REF:p. 24TOP:Manipulation 15.Which of the following is not a primary bond? a.Hydrogen b.Covalent c.Metallic d.Ionic ANS:A Primary bonds are the strongest bonds that hold atoms together because they involve the exchanging or sharing of electrons. There are three types of primary bonds: ionic bonds, covalent bonds, and metallic bonds. REF:p. 20TOP:Physical Structure (Primary Bonds) 16.The stability of a solid is evaluated by noting: a.its atomic mass and number. b.whether or not it is a compound. c.how hard the material is when set. d.whether the molecules are arranged uniformly. ANS:D The most stable solids have a regular crystalline structure with molecules in a regularly spaced pattern. If these molecules are arranged in a random form with no regular pattern, the solid is less stable and is called amorphous. REF:p. 21TOP:Physical Structure (Solids) 17.What is the maximum amount of stress a material can take before breaking? a.Ultimate capacity b.Ultimate strength c.Material hardness d.Maximum elasticity ANS:B The maximum amount of stress a material can withstand without breaking is known as its ultimate strength. REF:p. 22TOP:Physical Structure (Solids) 18.Metals that can withstand dimensional change without breaking are: a.tough. b.ductile. c.resilient. d.malleable. ANS:B The orthodontic wire being pulled or stretched under tension is a measure of its ductility, the amount of dimensional change it can withstand without breaking.REF:p. 22TOP:Physical Structure (Solids) 19.What is the measure of the weight of a material as compared with its volume? a.Density b.Viscosity c.Hardness d.Resistance ANS:A Density is a measure of the weight of a material as compared with its volume. Viscosity refers to the material’s ability to flow under pressure. Hardness is a material’s resistance to penetrations. REF:p. 21TOP:Physical Structure (Solids) 20.Of the following, which is not an application of a material’s classification? a.Longevity b.Utilization c.Fabrication d.All of these are correct. ANS:D Materials are classified by their application, how they will be utilized and fabricated, and their expected longevity. REF:p. 23TOP:Application 21.A _____ material will flow more easily under mechanical pressure. a.viscous b.thixotropic c.resistance d.therapeutic ANS:B Thixotropic materials are liquids that flow more easily under mechanical forces. REF:p. 23TOP:Physical Structure (Liquids) 22.Which of the following would be considered an indirect placement restorative material? a.Gold b.Gold foil c.Amalgam d.Composite resin ANS:A Some materials, because of convenience or toxic or other physically harmful characteristics, need to be fabricated indirectly outside the mouth and then placed into the oral environment. Porcelain, for instance, needs to be fired to temperatures higher than 1000 F; therefore, it must be fabricated indirectly. REF:p. 23TOP:Application23.What is the reaction initiated when a catalyst and a base are mixed together? a.Chemical b.Physical c.Dual d.All are possible reactions. ANS:D Chemical set materials are those that set through the timed chemical reaction of the catalyst and the base. Once the two components come in contact with each other, the chemical reaction begins and continues through the reaction stage. Light-activated materials use a blue light source to initiate the reaction stage. Both components are present in the material but do not react until the material comes in contact with the blue light source, thus giving the clinician unlimited working time. Dual set materials begin with initiation of the blue light source and then continue with a chemical set reaction; this also gives the clinician much better control of his or her working time. REF:pp. 24-25TOP:Reaction 24.Altering the set ratios of a material for any purpose will do what? a.Make the material harder b.Produce adverse results c.Speed up the initial set d.Have little significance ANS:B These ratio changes are variables that permit the clinician to alter manipulation and reaction times for some materials but are contraindicated with other materials because of adverse effects. Manufacturers give direction as to how much variation in ratio the material can withstand without adverse results and when this will occur. REF:p. 24TOP:Manipulation 25.What will happen if expired materials or improperly stored materials are used? a.Render the material ineffective b.Be of little consequence c.Cause a toxic reaction ANS:A The shelf life of a material refers to the deterioration and change in quality of the material over time. Attention to the date of expiration is important for consistency in the optimum characteristics of the product. Conditions of storage such as temperature and humidity, as well as type of storage container, may directly affect the material’s shelf life. REF:p. 24TOP:Manipulation MATCHING Match the items with the correct description below. a.Resistance to deformation b.The greatest stress a structure can withstand without permanent deformationc.The resistance of a solid to penetration d.The maximum amount of stress a material can withstand without breaking e.The ability of a material to resist fracture 1.Hardness 2.Ultimate strength 3.Stiffness 4.Proportional limit 5.Toughness 1.ANS:CREF:p. 21TOP:Physical Structure (Solids) 2.ANS:DREF:p. 22TOP:Physical Structure (Solids) 3.ANS:AREF:p. 22TOP:Physical Structure (Solids) 4.ANS:BREF:p. 22TOP:Physical Structure (Solids) 5.ANS:EREF:p. 22TOP:Physical Structure (Solids) Match the items with the correct description below. a.Begins when the material can no longer be manipulated in the mouth b.When the material has reached its ultimate state c.The amount of time the auxiliary has to bring the components together into a homogenous mix d.The time permitted to manipulate the material within the mouth 6.Mixing time 7.Working time 8.Initial set time 9.Final set time 6.ANS:CREF:p. 23TOP:Reaction 7.ANS:DREF:p. 24TOP:Reaction 8.ANS:AREF:p. 24TOP:Reaction 9.ANS:BREF:p. 24TOP:Reaction SHORT ANSWER 1.List and describe the three types of primary bonds. ANS: •Ionic bond: A metal gives an electron to an atom that needs extra electrons. •Covalent bond: Occurs when two atoms share electrons in their outer shell, creating full shells for both. •Metallic bond: The electrons in the outer shells are shared among all the atoms in the lattice with all the atoms positively charged. REF:p. 20TOP:Physical Structure (Primary Bonds) 2.List and describe the three different classifications of dental materials. ANS: