Dental Materials, The Oral Environment, and Oral Tissues

Question 1

what classification of dental materials do the following products belong to?

• materials that release therapeutic agents such as fluoride (ie. cements, liners and bases, glass ionomers
• materials that release remineralizing agents such as casein phosphopeptide (CPP) and amorphous calcium phosphate (ACP)

Answer 1

preventive dental materials

Question 2

what classification of dental materials do the following products belong to?

• metals, polymers, ceramics, and composites that repair or replaced damaged or missing tooth structure

Answer 2

restorative dental materials

Question 3

describe the differences between direct, indirect, temporary, and definitive restorative materials

Answer 3

• direct: placed, formed, contoured, and finished intraorally
• indirect: fabricated extraorally and then cemented (luted)
• temporary: materials used to restore teeth for a short period of time
• definitive: provide final, long-term treatment

Question 4

name 4 tissue engineering strategies of biomaterials

Answer 4

1. injection of cells
2. guided tissue regeneration
3. cell induction
4. scaffolds

Question 5

name 5 characteristics of ideal dental materials

Answer 5

1. biocompatible
2. bond permanently
3. match natural appearance of tooth and other visible tissues
4. exhibit properties similar to enamel, dentin, and other oral tissues
5. capable of initiating tissue repair or regenerating missing or damaged tissues

Question 6

what cells form enamel?

Answer 6

ameloblasts

Question 7

enamel apposition begins at the _____ and proceeds outward towards the surface of the tooth

Answer 7

DEJ

Question 8

enamel is made of very long ______ crystals about ___nm wide, but which may span the entire enamel thickness

Answer 8

hexagonal, 40

Question 9

enamel hexagonal crystals are packed into enamel ____ or ____ that are about ___ micro m across

Answer 9

rods, prisms, 5

Question 10

about ____ enamel crystals are needed to span the diameter of the prism

Answer 10

100

Question 11

how are enamel prisms revealed?

Answer 11

acid etching

Question 12

individual enamel crystals within a prism are coated with a thin layer of lipid and/or protein that plays a role in mineralization. this protein coat appears to increase enamel _____.

Answer 12

toughness

Question 13

what are prism sheaths?

Answer 13

• inter-rod enamel found between prisms
• contain organic components of enamel and have physical properties essential for enamel bonding
• permit the flow of water and ions in enamel demineralization and remineralization

Question 14

describe type III enamel etching

Answer 14

results in a uniform or mixed pattern of etching

Question 15

T or F:

differences in micromechanical bond strength of the different etching patterns has been established

Answer 15

false:

no differences have been established

Question 16

as etching is established, what appearance does it give the enamel surface?

Answer 16

a frosty appearance

Question 17

what is the purpose of the frosty, roughened surfaced produced by etching?

Answer 17

it provides a substrate for infiltration of bonding agents

Question 18

after bonding agents penetrate the roughened enamel surfaces formed by etching, they are _____, forming a ______ bond to the enamel surface.

Answer 18

polymerized, micromechanical

Question 19

T or F:

near the DEJ, enamel is commonly more prismatic, making it less difficult to etch

Answer 19

false:

enamel is commonly aprismatic at the DEJ, making it more difficult to etch

Question 20

why is surface enamel more difficult to etch compared to subsurface enamel?

Answer 20

• surface enamel has a significantly higher fluoride concentration compared to subsurface enamel

Question 21

what type of crystal structure does hydroxyapatite have?

Answer 21

hexagonal

Question 22

biological apatite has many more defects and chemical substitutions than ideal hydroxyapatite. what is the disadvantage of this?

Answer 22

makes the biological apatite less stable and more soluble in acids

Question 23

enamel and dentin hydroxyapatite is calcium deficient, carbonate-rich, and highly substituted. what are some common substitutes, and which is the most beneficial?

Answer 23

• Mg and Na substitute for Ca
• carbonate substitutes for phosphate and hydroxyl groups
• most beneficial: fluoride ion substitues for hydroxyl group, making the crystal stronger and less soluble

Question 24

what is a fluoroapatite mineral?

Answer 24

• results from the substitution of a fluoride ion for the hydroxyl group of a hydroxyapatite mineral
• it is less soluble than hydroxyapatite and provides more protection against caries

Question 25

what is odontogenesis?

Answer 25

the development of teeth and their supporting structures from embryonic tissues

Question 26

which cells are responsible for dentin formation?

Answer 26

odontoblasts

Question 27

which stage of tooth development do odontoblasts differentiate from the outer cells of the dental papilla?

Answer 27

the bell stage

Question 28

the pulp develops from the ____ cells of the dental papilla

Answer 28

central

Question 29

T or F: in tooth development, the basement membrane represents the location of the future DEJ

Answer 29

true

Question 30

what is the dentin-pulp complex?

Answer 30

the term used to describe dentin and pulp due to their similar embryonic origins

Question 31

where are odontoblasts found?

Answer 31

on the outer wall of the pulp, immediately medial to the advancing wall of dentin

Question 32

T or F: odontoblasts make dentin for the first half of the cell life only

Answer 32

false: they continue to make dentin throughout the life of the cell

Question 33

\_\_\_\_ are a distinct feature of dentin, and represent the tracks taken by _____ as they retreat from the DEJ during development.

Answer 33

tubules, odontoblasts

Question 34

T or F: tubule density and intertubular dentin is consistent from location to location inside dentin

Answer 34

false: tubules converge as they approach the pulp chamber, so tubule and intertubular dentin density and orientation varies from location to location

Question 35

the contents of dentin tubules are ______ and \_\_\_\_\_.

Answer 35

odontoblastic processes and fluid

Question 36

the extent that the odontoblastic process occupies the tubule has not been conclusively established, but at this time it is believed to extend to the \_\_\_\_.

Answer 36

DEJ

Question 37

what lines the dentin tubule lumen?

Answer 37

* a highly mineralized cuff of peritubular dentin aka intratubular dentin * contains mostly apatite crystals and little or no organic collagen matrix

Question 38

where is tertiary dentin found?

Answer 38

only under dentinal tubules that have been exposed to trauma, at the outer pulpal wall

Question 39

what is transparent/sclerotic dentin?

Answer 39

a type of tertiary dentin that develops following trauma, and is characterized by tubules being partially occluded with mineral

Question 40

what is the smear layer?

Answer 40

* a layer of debris left on a tooth surface following tooth preparation with a rotary instrument * the smear layer is removed by etching

Question 41

what effect does acid etching have on tubule lumen width?

Answer 41

the longer the acid etching, the wider the tubule lumen becomes

Question 42

why is bonding to transparent dentin difficult?

Answer 42

* tubules may retain plugs after etching due to the tendancy of transparent dentin tubules to be occluded with mineral

Question 43

T or F: an important element of dentin bonding technique is to keep the demineralized dentin dry

Answer 43

false: * demineralized dentin should be kept moist to avoid shrinkage of the dentin matrix and subsequent difficulty in penetration of the bonding agent to the tubules

Question 44

what is the significance of scalloping at the DEJ?

Answer 44

scalloping serves to increase the effective interfacial area and strengthen the bond between enamel and dentin

Question 45

during odontogenesis, the cells of the inner enamel epithelium differentiate into \_\_\_\_\_\_, and the outer cells of the dental papilla differentiate into \_\_\_\_\_.

Answer 45

preameloblasts, odontoblasts

Question 46

describe the role of odontoblasts in dentin formation

Answer 46

* they secrete dentin matrix on their side of the basement membrane * they then retreat into the central cells of the dental papilla as matrix and dentin is formed * at this point, the basement membrane desintegrates

Question 47

describe the role of ameloblasts in enamel formation

Answer 47

* after odontoblasts form dentin and the basement membrane disintegrates, preameloblasts differentiate into ameloblasts * ameloblasts secrete enamel matrix * the DEJ is established as these two hard tissues are formed

Question 48

what are enamel spindles the result of?

Answer 48

* before enamel forms, some of the developing odontoblastic processes extend into the ameloblast layer * when enamel formation begins, they become trapped as enamel spindles