421. A layer of cells that seems to be essential to enamel formation but does not actually secrete the enamel is:
A. Outer dental epithelium.
B. Stratum intermedium.
C. Reduced dental epithelium.
D. Vestibular lamina.
422. The stimulus that initiates the actual formation of enamel matrix seems to be:
A. Reduction of stellate reticulum.
B. Influence of increased vascularization of the dental sac.
C. Disappearance of the cell free zone of dental papilla.
D. Presence of predentin.
423. The number of roots that are formed is determined by the:
A. Number of root sheaths developed by the enamel organ.
B. Number of medial ingrowths at the epithelial diaphragm.
C. Number of root sheaths developed by the dental sac.
D. Thickness of the cervical loop.
424. Which of the following is the first process to occur in the sequence of tooth development:
A. Deposition of the first layer of enamel.
B. Deposition of the first layer of dentin.
C. Elongation of the inner dental epithelial cells.
D. Differentiation of odontoblasts.
425. All of the following are involved in the formation of a tooth except:
A. Epithelial root sheath.
B. Successional lamina.
C. Dental lamina.
D. Vestibular lamina.
426. The dental lamina initiating the permanent molars develops:
A. As successional lamina.
B. As a distal extension of the dental lamina.
C. As lateral dental lamina.
D. As vestibular lamina.
427.The cell rests of Malassez are derivatives of:
A. Cervical ameloblasts.
B. Outer enamel epithelium.
C. Dental papilla.
D. Root sheath.
428.Odontogenesis of the primary dentition begins between:
A. The sixth & seventh week.
B. The fifth & sixth week.
C. The seventh& eighth week.
D. The fourth & fifth week.
429. The embryo’s stomodeum is lined by:
A. Ectoderm.
B. Endoderm.
C. Mesoderm.
D.Ectomesenchyme.
430. By the 6th week of tooth development, the oral epithelium is:
A. 2-3 layers thickness.
B. 3-4 layers thickness.
C. 4-5 layers thickness.
D. 2-5 layers thickness.
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