The prognosis for internal bleaching is best if the etiology of the stain is:

 # The prognosis for internal bleaching is best if the etiology of the stain is:

A. Amalgam restorations

B. Necrotic pulp tissue

C. Precipitation of metallic salts

D. Silver containing root canal sealers

The correct answer is B. Necrotic pulp tissue.

Internal bleaching treatments are most effective among root canal treated teeth which have internal stains or discoloration due to blood, necrotic tissues and fluids that could have leaked in prior to root canal therapy.

Internal tooth bleaching is done by placing peroxide directly into the pulp chamber of a root canal treated tooth. The peroxide will then directly work on the stains within the tooth structure.

Staining from the silver containing root canal sealers and from mercury of amalgam restorations appear very dark. These stains are seldom treated by bleaching. Restorative treatments provide the most esthetic result because they remove or cover up these stains. 

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Which of the following types of fibers are found in loose connective tissue?

 # Which of the following types of fibers are found in loose connective tissue? 

a. Yellow elastic and white collagen. 

b. White fibrous, elastic, and reticular. 

c. Elastic and collagenous. 

d. Fine reticular

The correct answer is: A. Yellow elastic and white collagen.

Yellow elastic and white collagen are found in loose connective tissue. White fibrous, elastic, and reticular fibers are found in dense irregular connective tissue. Elastic and collagenous fibers are found in elastic cartilage. Fine reticular fibers are found in reticular tissue. 

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Bone replaces cartilage by which of the following processes?

# Bone replaces cartilage by which of the following processes? 

a. Interstitial growth

b. Endochondral development

c. Intramembranous bone formation

d. Membranous bone formation

The correct answer is: B. Endochondral development.

Interstitial growth is growth within the cartilage matrix by each cartilage cell enlarging

and forming matrix around each cell.

Bone replaces cartilage by a process termed endochondral bone development.

Intramembranous bone is formed when collagen fibers of connective tissue organize into closely knit meshwork, and this matrix gradually calcifies into bone.

Intramembranous bone formation is also known as membranous bone formation.

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The cerebral hemispheres develop from which of the following vesicles:

 # The cerebral hemispheres develop from which of the following vesicles? 

a. Forebrain

b. Midbrain

c. Hindbrain

d. Primary brain

The correct answer is a. Forebrain.

 The cerebral hemispheres develop from the forebrain vesicles.

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The first step of mitosis is:

 # The first step of mitosis is which of the following? 

a. Telophase

b. Metaphase

c. Prophase

d. Anaphase 

The correct answer is: C. Prophase.

Prophase is the first step of mitosis in which four structural changes occur.

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Melanoblastoma are derived from:

 # Melanoblastoma are derived from:

A. Basal epidermal cells

B. Neural crest cells

C. Prickle cells of epidermis

D. Somato pleuric mesoderm

The correct answer is B. Neural crest cells.

Melanoblastoma are derived from Neural crest cells.

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Notochord develops in:

 # Notochord develops in:

A. 3rd week

B. 3rd month

C. 6th month

D. 10th month

The correct answer is A. 3rd week.

The notochord arises from axial mesoderm at about 16 days and is completely formed by the beginning of the fourth week. It defines the longitudinal axis of the embryo, determines the orientation of the vertebral column, and persists as the nucleus pulposus of the intervertebral discs.

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