581. Which of the following is a true statement about the organic matrix of the newly synthesized enamel?
A.It represents 30% by weight of the organic content.
B.It has a high content of amelogenins.
C.It contains collagen fibers.
D.It has a high inorganic content.

582. Which of the following is the source of nutrient supply to the secretory ameloblasts during early crown formation?
A.Subodontoblastic plexus of capillaries.
B. Central blood vessels in the dental papilla.
C. Dental sac capillaries adjacent to the epithelial diaphragm.
D. Dental sac capillaries adjacent to the outer dental epithelium.

583. Tome’s processes:
A. Contain mitochondria, but lack Golgi saccules and rough endoplasmic reticulum.
B. Lack secretory granules.
C. Indent the immature enamel to produce a serrated outline on its appositional surface.
D.Are located at the proximal end of the ameloblast.

584. Neonatal lines are found in all the following except:
A. Enamel of primary incisors.
B. Enamel of permanent first molar.
C. Enamel of permanent second molars.
D. Enamel of primary molars.

585.Hypocalcified ectodermal structures in enamel are:
A. Spindles and lamellae.
B. Odontoblastic processes and tufts.
C. Tufts and spindles.
D. Lamellae type A,and tufts.

586. Which of the following most correctly describes the significance of Hunter Schreger bands?
A. It indicates variation in size of enamel rods.
B. It reflects variations in the length of enamel rods.
C. It represents hypercalcified areas in cervical enamel.
D. It is an optical effect that is not related to variations in enamel structure.

587. The orientation of hydroxyapatite crystals in enamel, the greatest crystal density would be present in:
A.enamel lamellae.
B.The interrod region.
C.The prismless layer.
D.Gnarled enamel.

588.Perikymata:
A.Are oriented parallel to the long axis of the crown (tooth).
B.Are surface manifestation of Retzius lines.
C.Are only located in prismless enamel.
D.Produce the scalloping seen along the DEJ.

589.Unmineralized structures seen in the enamel are :
A. Cross striations.
B. Enamel tufts.
C. Incremental lines of Retzius.
D. Enamel spindles.

590. All of the following statements about the incremental lines of Retzius in enamel are true except:
A. They run as concentric lines over the cusp.
B.Perikymata are outer manifestations of it.
C. They are formed as result of rhythmic apposition.
D. They do not reach the cervical region.

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