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:
            tooth eruption and throughout the
life of the pulp.
The dentin forming the initial shape of the tooth is
called primary dentin and is usually completed 3
years
after
tooth
eruption
(in
the
case
of
permanent teeth).
www.drcube.org
Dentinal Tubules
The dentinal tubules are small canal that remain from the process of dentinogenesis and
extend through the entire width of dentin, from the pulp to the DEJ.
Each tubule contains the cytoplasmic cell process (Tome's fiber) of an odontoblast and is
lined with a layer of peritubular dentin, which is much more mineralized than the
surrounding intertubular dentin . The tubules comprise about 10% of dentin volume.
www.drcube.org
In mature dentin, the odontoblastic process extends
within the dentinal tubule to about one-third the
dentinal thickness.
The number of tubules increases from 15,000 to
20,000/mm2 at the DEJ to 45,000 to 65,000/mm2 at
the pulp.
The lumen of the tubules also varies from the DEJ to
the pulp surface. In coronal dentin, the average
diameter of tubules at the DEJ is 0.5 to 0.9 μm, but
this increases to 2 to 3 μm near the pulp.
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Tubules are generally oriented perpendicular to the
DEJ. Along the tubule walls are small lateral openings
called canaliculi or lateral canals.
The lateral canals are formed as a result of the
presence of secondary (lateral) branches of adjacent
odontoblastic processes during dentinogenesis.
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Dentinoenamel Junction
It is the transition between the highlymineralized
enamel and the collagen-containing dentin.
DEJ must resist fracture and separation under the
extreme forces from occlusal loading.
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Dentinoenamel Junction
DEJ width falls within a range of 2 to 15
μm. Some collagen fibers from the
dentinal material extend through this
transitional area and are embedded in
the more highly mineralized enamel.
These embedded collagen fibers may
also add to the overall strength and
resilience of the junction between the
two tissues.
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Dentin Composition
Mature dentin is a crystalline material that is less
hard than enamel but slightly harder than bone.
The odontoblast, with its cell body at the pulp
periphery and its extended process within the
dentinal tubule, secretes the organic dentin matrix
and regulates mineralization.
Mature
dentin
is
45%
-
50%
inorganic
or
mineralized material, 30% organic material, and
25% water. The organic material is approximately
90% type I collagen and 10% non-collagenous
proteins.
www.drcube.org
The crystalline formation of mature dentin mainly
consists of calcium hydroxyapatite with the chemical
formula of Ca10(PO4)6(OH)2.
The calcium hydroxyapatite found in dentin is similar
to that found in a higher percentage in enamel and in
lower percentages in both cementum and bone tissue.
In addition, the crystals in dentin are platelike in shape
and 30% smaller in size than those in enamel.
The thickness of the apatite crystals varies from 3.5
nm near the DEJ to about 2 nm close to the pulp

            Quiz: