Chapter 02: Oral Environment and Patient Considerations
MULTIPLE CHOICE
1. Some dental materials may be therapeutic in small quantities or if in contact
... [Show More] 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. tensionTEST BANK FOR DENTAL MATERIALS 3RD EDITION BY HATRICK
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 [Show Less]