Chapter_02

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School

Fortis Institute, Scranton *

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101

Subject

Chemistry

Date

Apr 3, 2024

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rtf

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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. DIF: Analyze REF: Biocompatibility | p. 10 OBJ: 1 TOP: NBDHE, Providing Supportive Treatment Services 6.1 | CODA, Restorative/Dental Materials and Procedures 1 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. DIF: Remember REF: Biocompatibility | p. 11 OBJ: 1 TOP: NBDHE, Providing Supportive Treatment Services 6.1 | CODA, Restorative/Dental Materials and Procedures 1 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.

DIF: Understand REF: Biocompatibility | p. 11 OBJ: 1 TOP: NBDHE, Providing Supportive Treatment Services 6.1 | CODA, Restorative/Dental Materials and Procedures 1 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 c. compression d. chemical bonding ANS: A 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. DIF: Apply REF: Force, Stress and Strain | p. 12 OBJ: 1 TOP: NBDHE, Providing Supportive Treatment Services 6.1 | CODA, Restorative/Dental Materials and Procedures 1 5. How much force do denture wearers apply as compared to individuals with intact dentitions? a. 40% b. 50% c. 60% d. 70% ANS: C Denture wearers apply 40% less force than patients with intact dentitions, thus, using 60% force during mastication. DIF: Remember REF: Classification of Dental Materials | Force and Stress | p. 11 OBJ: 3 TOP: NBDHE, Providing Supportive Treatment Services 6.1 | CODA, Restorative/Dental Materials and Procedures 1 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. DIF: Apply REF: Force, Stress and Strain | p. 13 OBJ: 3

TOP: NBDHE, Providing Supportive Treatment Services 6.1 | CODA, Restorative/Dental Materials and Procedures 1 7. How does force exerted over a large area compare to force exerted over a small area when the same force is applied to each? a. Deformation is greater in a small area than in a large area. b. Compression on objects in the large area are shortened more than in the small area. c. There is little difference in outcome whether the area is large or small. d. It will depend on how poorly the force is dissipated over each area. ANS: A The amount of distortion is determined on the size of the force. Force applied to a small area will cause greater distortion than over a large area. Objects are shortened as a result of compressive force. The larger the area helps dissipate the impact of the force. DIF: Understand REF: Classification of Dental Materials | Force and Stress | p. 12 OBJ: 3 TOP: NBDHE, Providing Supportive Treatment Services 6.1 | CODA, Restorative/Dental Materials and Procedures 1 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. DIF: Remember REF: Water Sorption | p. 14 OBJ: 1 TOP: NBDHE, Providing Supportive Treatment Services 6.1 | CODA, Restorative/Dental Materials and Procedures 1 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. DIF: Understand REF: Corrosion | p. 14 OBJ: 1 TOP: NBDHE, Providing Supportive Treatment Services 6.1 | CODA, Restorative/Dental

Materials and Procedures 1 10. Which of the following has been suggested to delay formation of surface tarnish on dental amalgams? a. Polishing b. Undercondensation c. Incremental addition d. Use of low-copper amalgam ANS: A 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. DIF: Understand REF: Corrosion | p. 14 OBJ: 6 TOP: NBDHE, Providing Supportive Treatment Services 6.1 | CODA, Restorative/Dental Materials and Procedures 1 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. DIF: Understand REF: Galvanism | p. 15 OBJ: 6 TOP: NBDHE, Providing Supportive Treatment Services 6.1 | CODA, Restorative/Dental Materials and Procedures 1 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.

DIF: Understand REF: Expansion and Contraction | p. 15 OBJ: 7 TOP: NBDHE, Providing Supportive Treatment Services 6.1 | CODA, Restorative/Dental Materials and Procedures 1 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. DIF: Understand REF: Expansion and Contraction | p. 15 OBJ: 7 TOP: NBDHE, Providing Supportive Treatment Services 6.1 | CODA, Restorative/Dental Materials and Procedures 1 14. Mechanical retention is the result of adhesion whereas chemical retention uses undercuts for retention. When significant tooth structure is lost, undercuts are no longer effective for retention. a. Both statements are current. b. Neither statement is correct. c. Statement 1 is correct; statement 2 is incorrect. d. Statement 1 is incorrect; statement 2 is correct. ANS: D Mechanical retention uses undercuts to retain a restoration in the preparation while chemical retention relies on adhesion. When significant tooth structure is lost, the cusps or other parts of the tooth are undermined and weakened. An indirect restoration such as a crown would become the standard of care. DIF: Analyze REF: Retention | p. 16 OBJ: 8 TOP: NBDHE, Providing Supportive Treatment Services 6.1 | CODA, Restorative/Dental Materials and Procedures 1 15. 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

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