‘Chicken-wire’ appearance of enlarged bone marrow spaces is seen in:

 # ‘Chicken-wire’ appearance of enlarged bone marrow spaces is seen in:

A. Fetal alcohol syndrome

B. Sickle cell anemia

C. Hemophilia A

D. Beta thalassemia major

The correct answer is D. Beta thalassemia major.

Radiographic changes of thalassemia include generalized rarefaction of alveolar bone, chicken-wire appearance of enlarged marrow spaces and coarse trabeculation. In the skull, proliferation of marrow may completely erode the cortex, leaving only periosteum, and produce a ‘hair-on-end’ radiographic appearance.

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Enamel can act in a sense like a:

# Enamel can act in a sense like a:

A. Permeable membrane

B. Impermeable membrane

C. Semipermeable membrane

D. Infrapermeable membrane

 

The correct answer is C. Semipermeable membrane.

Another physical property of enamel is its permeability. It has been found with radioactive tracers that the enamel can act in a sense like a semipermeable membrane, permitting complete or partial passage of certain molecules: 14C-labeled urea, I, etc. The same phenomenon has also been demonstrated by means of dyes.

Reference: Orban's

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All primary teeth would have begun to calcify by:

 # All primary teeth would have begun to calcify by:

A. 14 weeks of intrauterine life

B. 18-20 weeks of intrauterine life

C. 6 months of gestation

D. 6 months of age

The correct answer is B. 18-20 weeks of intrauterine life.

Calcification of the primary teeth begins in utero from 13 to 16 weeks postfertilization. By 18 to 20 weeks, all the primary teeth have begun to calcify. Primary tooth crown formation takes only about 2 to 3 years from initial calcification to root completion. However, mineralization of the permanent dentition is entirely postnatal, and the formation of each tooth takes about 8 to 12 years.

Reference: Wheeler's

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Major salivary buffer is:

 # Major salivary buffer is:

A. Protein buffer

B. Carbonic acid and bicarbonate

C. Phosphate buffer

D. Albumin

The correct answer is B. Carbonic acid and bicarbonate.

The maintenance of the physiologic hydrogen ion concentration (pH) at the mucosal epithelial cell surface and the tooth surface is an important function of salivary buffers. The primary effect of these buffers has been studied in relationship to dental caries. In saliva, the most important salivary buffer is the bicarbonate– carbonic acid system. Saliva also contains coagulation factors (i.e., factors VIII, IX,

and X; plasma thromboplastin antecedent; and Hageman factor) that hasten blood coagulation and that protect wounds from bacterial invasion. An active fibrinolytic enzyme may also be present. 

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