The successor of the deciduous teeth develops from:

 # The successor of the deciduous teeth develops from:

A. Lingual extension of the dental lamina

B. Labial extension of the dental lamina

C. Buccal extension of the dental lamina

D. Occlusal extension of the dental lamina

The correct answer is A. Lingual extension of the dental lamina

The initiation of the permanent first, second and third molars occurs at the fourth month of intrauterine life, one year after birth and five years after birth respectively. The lingual extension of dental lamina is called successional lamina. Successional lamina is responsible for the development of permanent incisors, canine and premolars. The successional lamina is active from the fifth month in utero (for the permanent central incisor) to ten months of age (second premolar).

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Final stage of tooth development

 # What is the final stage of tooth development?

a. Crown formation.

b. Root formation and eruption.

c. Function.

d. Dentinogenesis and amelogenesis.

The correct answer is C. Function.

Crown formation is followed by root formation and eruption. Root formation and eruption are followed by function. Function is the final stage of tooth development. Dentinogenesis and amelogenesis are followed by crown formation.

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Bilateral nasal placodes appear during:

 # During which week of development do the bilateral nasal placodes appear?

a. Fourth.

b. Fifth.

c. Sixth.

d. Seventh.

The correct answer is b. Fifth.

During the fifth week, the bilateral nasal placodes, or thickened areas of epithelium,

appear in the upper border of the lip.

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Palatal shelf elevation takes place during:

 # Palatal shelf elevation takes place during which prenatal week of development? 

a. Week 7. 

b. Week 8. 

c. Week 9. 

d. Week 10

The correct answer is: B. Week 8.

Palatal shelf elevation occurs during the eighth prenatal week.

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Zone of fusion between the medial nasal and maxillary process

 # The zone of fusion between the medial nasal and maxillary process is referred to as which of the following? 

a. Cleft lip. 

b. Philtrum. 

c. Nasal fin. 

d. Maxillonasal process.

The correct answer is C. Nasal fin.

A lack of contact or fusion of the medial nasal and maxillary processes results in either a unilateral or bilateral cleft lip. The medial nasal process is called the philtrum. The epithelial coverings of the medial nasal and maxillary processes normally contact and create a zone of fusion termed the nasal fin. 

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Meckel's cartilage is replaced by:

 # Which of the following replace Meckel’s cartilage? 

a. The body of the mandible and the cartilaginous condyle. 

b. The body of the mandible and the condylar unit. 

c. The condylar unit and the angular process. 

d. The alveolar process and the cartilaginous condyle.

The correct answer is: A. The body of the mandible and the cartilaginous condyle.

Together, the body of the mandible and the cartilaginous condyle replace Meckel’s cartilage. The body of the mandible and the condylar unit do not replace Meckel’s cartilage. The condylar unit and the angular process do not replace Meckel’s cartilage. The alveolar process and the cartilaginous condyle do not replace Meckel’s cartilage.

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Face and brain are first supplied by:

 # The face and brain are first supplied by which of the following arteries? 

a. Internal carotid artery. 

b. External carotid artery. 

c. Common carotid artery. 

d. Stapedial artery.

The correct answer is A. Internal carotid artery.

The face and brain are first supplied by the internal carotid artery. The facial vessels form at 7 weeks and then detach from the internal carotid artery and attach to the external carotid artery. The face and brain are first supplied by the internal carotid artery, not by the common carotid artery. The face and brain are first supplied by the internal carotid artery, not by the stapedial artery.

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