Pretend you are a teacher preparing a quiz for the text I will provide. 
            Each quiz question should follow the format below. 
            Ensure that you carefully recheck the questions and answers for accuracy. 
            The output should be a ready-to-use list of dictionaries for the Python eval function:

            [

                    "question": "WRITE THE QUESTION HERE",
                    "options": ["A) OPTION_1", "B) OPTION_2", "C) OPTION_3", "D) OPTION_4"],
                    "answer": INDEX_OF_CORRECT_ANSWER_IN_OPTIONS_LIST,
                    "explanation": "EXPLAIN WHY THE ANSWER IS CORRECT"

            ]

            Text:
            eral content of
dentin increases with age.
www.drcube.org
Structurally there are two main types of dentin which are:
1. Intertubular dentin: the primary structural
component of it is the hydroxyapatite- embedded
collagen
matrix
between
tubules.
Intertubular
dentin forming the bulk of dentin structure.
2. Peritubular dentin: it is the hypermineralized
dentin limited to the walls of dentinal tubules. The
walls of the dentinal tubules (peritubular dentin) in
the
primary
dentin
gradually
thicken,
through
ongoing mineral deposition, with age. The dentin
therefore becomes harder, denser, and, because
tubular fluid low becomes more restricted as the
lumen spaces become smaller, less sensitive.
www.drcube.org
The increased amount of mineral in the primary dentin
is defined as dentin sclerosis. Dentin sclerosis resulting
from aging is called physiologic dentin sclerosis.
The dentinal tubules in the Outer Dentin which is
near
the
DEJ
are
relatively
far
apart
and
the
Intertubular dentin makes up 96% of the surface area.
In the Inner Dentin, the tubules diameters are larger
and the distance between tubule centers is half that of
tubules at DEJ. Thus, the intertubular matrix area is
only 12% of the surface area, and the permeability of
inner dentin is about eight times more permeable than
the dentin near DEJ.
www.drcube.org
Physiologic and Tertiary Dentin
Some of the variations in the dentinal tissue occur
during its natural sequence of development or aging,
while other variations result from the effects of
external factors on the tooth, such as caries, injury, or
wear. An understanding of these variations in the
dentinal tissue is important because they are related
to the long-term success of dental procedures and
therapies.
Physiologic dentin
Odontoblasts synthesize and secrete extracellular
organic matrix, which, following mineralization, forms
the primary and secondary physiologic dentin
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Formed relatively quickly until root formation is
completed by odontoblasts. The first-formed,
150-μm-thick layer of primary dentin subjacent to
the enamel is termed mantle dentin.
It differs from other primary dentin in that it is 4%
less
mineralized,
and
the
collagen
fiber
orientation is perpendicular rather than parallel
to the DEJ.
1. Primary Dentin
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The odontoblasts produce primary dentin, mainly
intertubular dentin, at a rate of 4 to 8 μm/day.
Approximately 2 to 3 years following tooth
eruption. The bulk of dentin surrounding the pulp
chamber and canal systems, termed circumpulpal
dentin.
The synthesis of dentin then slows to 1 to 2
μm/day,
decreasing
in
rate
with
age
but
continuing as long as the tooth is vital.
www.drcube.org
This is a slowly formed dentin of 1 to 2 μm/day,
decreasing in rate with age but continuing as long
as the tooth is vital.
This continued deposition of secondary dentin
led to constriction in the dimensions of the pulp
chamber.
In response to mild occlusal stimulus, secondary
dentin is mainly deposited in the pulp

            Quiz: