Dental Materials, The Oral Environment, and Oral Tissues Flashcards
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)
preventive dental materials
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
restorative dental materials
describe the differences between direct, indirect, temporary, and definitive restorative materials
- 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
name 4 tissue engineering strategies of biomaterials
- injection of cells
- guided tissue regeneration
- cell induction
- scaffolds
name 5 characteristics of ideal dental materials
- biocompatible
- bond permanently
- match natural appearance of tooth and other visible tissues
- exhibit properties similar to enamel, dentin, and other oral tissues
- capable of initiating tissue repair or regenerating missing or damaged tissues
what cells form enamel?
ameloblasts
enamel apposition begins at the _____ and proceeds outward towards the surface of the tooth
DEJ
enamel is made of very long ______ crystals about ___nm wide, but which may span the entire enamel thickness
hexagonal, 40
enamel hexagonal crystals are packed into enamel ____ or ____ that are about ___ micro m across
rods, prisms, 5
about ____ enamel crystals are needed to span the diameter of the prism
100
how are enamel prisms revealed?
acid etching
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 _____.
toughness
what are prism sheaths?
- 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
describe type III enamel etching
results in a uniform or mixed pattern of etching
T or F:
differences in micromechanical bond strength of the different etching patterns has been established
false:
no differences have been established
as etching is established, what appearance does it give the enamel surface?
a frosty appearance
what is the purpose of the frosty, roughened surfaced produced by etching?
it provides a substrate for infiltration of bonding agents
after bonding agents penetrate the roughened enamel surfaces formed by etching, they are _____, forming a ______ bond to the enamel surface.
polymerized, micromechanical
T or F:
near the DEJ, enamel is commonly more prismatic, making it less difficult to etch
false:
enamel is commonly aprismatic at the DEJ, making it more difficult to etch
why is surface enamel more difficult to etch compared to subsurface enamel?
- surface enamel has a significantly higher fluoride concentration compared to subsurface enamel
what type of crystal structure does hydroxyapatite have?
hexagonal
biological apatite has many more defects and chemical substitutions than ideal hydroxyapatite. what is the disadvantage of this?
makes the biological apatite less stable and more soluble in acids
enamel and dentin hydroxyapatite is calcium deficient, carbonate-rich, and highly substituted. what are some common substitutes, and which is the most beneficial?
- 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
what is a fluoroapatite mineral?
- 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
what is odontogenesis?
the development of teeth and their supporting structures from embryonic tissues
which cells are responsible for dentin formation?
odontoblasts
which stage of tooth development do odontoblasts differentiate from the outer cells of the dental papilla?
the bell stage
the pulp develops from the ____ cells of the dental papilla
central
T or F:
in tooth development, the basement membrane represents the location of the future DEJ
true
what is the dentin-pulp complex?
the term used to describe dentin and pulp due to their similar embryonic origins
where are odontoblasts found?
on the outer wall of the pulp, immediately medial to the advancing wall of dentin
T or F:
odontoblasts make dentin for the first half of the cell life only
false:
they continue to make dentin throughout the life of the cell
____ are a distinct feature of dentin, and represent the tracks taken by _____ as they retreat from the DEJ during development.
tubules, odontoblasts
T or F:
tubule density and intertubular dentin is consistent from location to location inside dentin
false:
tubules converge as they approach the pulp chamber, so tubule and intertubular dentin density and orientation varies from location to location
the contents of dentin tubules are ______ and _____.
odontoblastic processes and fluid
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 ____.
DEJ
what lines the dentin tubule lumen?
- a highly mineralized cuff of peritubular dentin aka intratubular dentin
- contains mostly apatite crystals and little or no organic collagen matrix
where is tertiary dentin found?
only under dentinal tubules that have been exposed to trauma, at the outer pulpal wall
what is transparent/sclerotic dentin?
a type of tertiary dentin that develops following trauma, and is characterized by tubules being partially occluded with mineral
what is the smear layer?
- a layer of debris left on a tooth surface following tooth preparation with a rotary instrument
- the smear layer is removed by etching
what effect does acid etching have on tubule lumen width?
the longer the acid etching, the wider the tubule lumen becomes
why is bonding to transparent dentin difficult?
- tubules may retain plugs after etching due to the tendancy of transparent dentin tubules to be occluded with mineral
T or F:
an important element of dentin bonding technique is to keep the demineralized dentin dry
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
what is the significance of scalloping at the DEJ?
scalloping serves to increase the effective interfacial area and strengthen the bond between enamel and dentin
during odontogenesis, the cells of the inner enamel epithelium differentiate into ______, and the outer cells of the dental papilla differentiate into _____.
preameloblasts, odontoblasts
describe the role of odontoblasts in dentin formation
- 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
describe the role of ameloblasts in enamel formation
- 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
what are enamel spindles the result of?
- before enamel forms, some of the developing odontoblastic processes extend into the ameloblast layer
- when enamel formation begins, they become trapped as enamel spindles
