TEST BANK FOR DENTAL MATERIALS 3RD EDITION BY HATRICK

Chapter 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 ir ...

Chapter 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. 9 TOP: 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. 10 TOP: 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. 10 TOP: 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. tension TEST BANK FOR DENTAL MATERIALS 3RD EDITION BY HATRICK NURSINGTB.COMNURSINGTB.COM c. 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. 11 TOP: 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. 11 TOP: 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. TEST BANK FOR DENTAL MATERIALS 3RD EDITION BY HATRICK NURSINGTB.COM