The common organism implicated in dry socket is:

 # The common organism implicated in dry socket is:

A. Streptococcus

B. Staphylococcus

C. Treponema denticola

D. Pneumococcus

The correct answer is C. Treponema denticola.

A number of bacteria are known to possess fibrinolytic activity. It has been recently postulated

that Treponema denticola may have an etiological role in the genesis of dry socket.

Irregular opaque areas are found on radiographs of lower anterior teeth, the teeth are vital. The cause may be:

 # Irregular opaque areas are found on radiographs of lower anterior teeth, the teeth are vital. The cause may be: 

A. Subgingival calculus 

B. Cementoma

C. Condensing osteitis 

D Chronic apical periodontitis 

The correct answer is A. Subgingival calculus.

Calculus may be seen as small angular radiopaque deposits projecting between interproximal surfaces of the teeth or as radiopaque bands across the roots representing circumferential accumulation as illustrated in the figure.

Ref: White, S.C. and Pharoah, M.J., 2014. Oral radiology-E-Book: Principles and interpretation. Elsevier Health Sciences.

Head diameter of a 245 bur is:

 # Head diameter of a 245 bur is:

A. 0.1 mm

B. 0.5 mm

C. 0.8 mm

D. 0.9 mm

The correct answer is C. 0.8 mm.

No. 245 bur has a head length of 3 mm and head diameter of 0.8 mm. This is an inverted cone carbide bur used for amalgam cavity preparations. 

Benefits of the bur: 

• For amalgam cavity preparations, the initial punch cut should have a depth of 1.5 mm, so it is half of this bur length, so it is very convenient to use the bur. 

• In class II the proximal ditch cut is established easily with the 0.8 mm diameter bur end cuts 0.5 mm into dentin and 0.3 mm into enamel. 

During countercurrent mechanisms, which of the following area of nephron does filtrate become hypertonic to plasma?

 # During countercurrent mechanisms, which of the following area of nephron does filtrate become hypertonic to plasma?

A. Bowman’s capsule

B. Proximal convoluted tubule

C. Loop of Henle

D. Distal convoluted tubule

The correct answer is C. Loop of Henle.

A circuit of fluid in the loop of Henle—an important part of the kidneys—allows for gradual buildup of the concentration of urine in the kidneys, by using active transport on the exiting nephrons (tubules carrying liquid in the process of gradually concentrating the urea). The active transport pumps need only to overcome a constant and low gradient of concentration, because of the countercurrent multiplier mechanism.