451. Determination of the initial position of the first cusp of the tooth during crown pattern formation may be achieved by:
A. The enamel knot.
B. The enamel cord.
C. Both enamel knot and cord.
D. None of the above.

452. Before enamel formation begins:
A. Enamel knot disappears and enamel cord remains.
B. Enamel knot remains and enamel cord disappear.
C. Both knot and cord disappear.
D. Both knot and cord remain.

453. Concerning the stellate reticulum one of the following statements is wrong:
A. Occupies the central portion of the dental organ.
B. Lies between outer and inner dental epithelia.
C. Synthesizes and secretes glucoseaminoglycans.
D. Becomes polyhedral in shape.

454. The dental sac is:
A. The condensation of the ectomesenchymal cells surrounding the dental organ.
B. The condensation of the ectomesenchymal cells surrounding the dentalpapilla.
C. The condensation of the ectomesenchymal cells surrounding the dental organand dental papilla.
D. None of the above.

455. The main difference between bell and apposition stage is:
A. The formation of first layer of E.
B. The formation of first layer of D.
C. The formation of first layer of C.
D. The formation of first layer alveolar bone.

456. Concerning the stratum intermedium, one of the following statements is incorrect:
A. It is composed of 2-3 layers of squamous epithelial cells.
B. It is differentiated between the inner enamel epithelium and stellate reticulum.
C. It is connected to each other and to the cells of stratum intermedium bydesmosomes.
D. It is essential for enamel formation as it contains acid phosphatase enzyme.

457. Which one of the following functions of the inner dental epithelium is wrong?
A. It exerts an organizing influence on the undifferentiated cells of the dentalpapilla to differentiate into ameloblasts.
B. It shares in the transport of the nutritive materials.
C. It determines the future incisal or occlusal crown pattern.
D. It lays down enamel matrix and helps in its mineralization.

458. The epithelial root sheath of Hertwig can’t be seen as a continuous layer in the developing root because:
A. The rapid epithelial sheath proliferation.
B. The dentin formation.
C. The rapid epithelial sheath destruction after dentin formation.
D. All of the above.

459. Epithelial rests of Malassez are:
A. Epithelial strands and may undergo degeneration only.
B. Epithelial remnants of the epithelial root sheath of Hertwig only.
C. Network or isolated islands in the P.L. only,
D. All of the above.

460. If Hertwig’s epithelial root sheath does not disintegrate:
A. No cementum will be formed on the radicular dentin.
B. It is likely that some of the enamel will be resorbed.
C. The apical end of the junctional epithelium will lie occlusal to the cement-enamel junction.
D.Predentine will form on the outer surface of the radicular dentin.

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