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Silicone differs from polyether polymer with respect to:

 # Silicone differs from polyether polymer with respect to:
A. Affinity for water
B. Place and time of one
C. Area of one
D. Cost effectiveness



The correct answer is A. Affinity for water.

One of the disadvantages of the silicone impression materials (including condensation silicones) is their inherent hydrophobic nature. A nonionic surfactant can be added to the paste in the manufacturing process to render a degree of hydrophilicity to the surface of the material. This surfactant migrates toward the surface of the impression material and has its hydrophilic segment oriented toward the surface—a phenomenon that makes the surface more wettable by water. These impression materials still require a dry field for impression making. Pouring the set impression with a gypsum forming
mixture is facilitated because the wet stone has a greater affinity for the hydrophilic surface. The clinical significance of hydrophilic additives is discussed in subsequent sections.

One of the best agents used in successful pulp capping is:

 # One of the best agents used in successful pulp capping is:
A. Copper cement
B. Calcium hydroxide
C. Amalgam
D. Zinc oxide



The correct answer is B. Calcium hydroxide.

Calcium hydroxide, because of its high pH value, acts as a pulp irritant and stimulates reparative dentine formation . It is also used as a pulp-capping agent, both in direct and indirect pulp capping.

The principal ingredient of an irreversible hydrocolloid impression is:

 #  The principal ingredient of an irreversible hydrocolloid impression is:
A. Agar
B. Tri sodium phosphate
C. Sodium alginate
D. Colloidal silica


The correct answer is C. Sodium alginate.

The chief active ingredient in the alginate impression materials is one of the soluble alginates, such as sodium, potassium, or triethanolamine alginate.

The diatomaceous earth acts as a filler to increase the strength and stiffness of the alginate gel. It also produces a smooth texture and ensures the formation of a firm gel surface that is not tacky.

Metal that expands on solidification from the molten state is:

 # A metal that expands on solidification from the molten state is:
A. Gold
B. Silver
C. Bismuth
D. Copper



The correct answer is C. Bismuth.

Elemental bismuth is denser in the liquid phase than the solid, a characteristic it shares with germanium, silicon, gallium, and water. Bismuth expands 3.32% on solidification; therefore, it was long a component of low-melting typesetting alloys, where it compensated for the contraction of the other alloying components to form almost isostatic bismuth-lead eutectic alloys.

Self Appendectomy Performed by a Soviet General Practitioner

 A Soviet General Practitioner, Leonid Ivanovich Rogozov, had developed appendicitis while at Novolazarevskaya Station in April 1961, and being the only medical professional there at the time, had to perform his own appendectomy. 

Leonid Ivanovich Rogozov performing self Appendectomy



On the morning of 29 April 1961, Rogozov experienced general weakness, nausea, and moderate fever, and later pain in the lower right portion of his abdomen. None of the possible conservative treatments helped. By 30 April signs of localised peritonitis became apparent, and his condition worsened considerably by the evening. Mirny, the nearest Soviet research station, was more than 1,000 miles from Novolazarevskaya. Antarctic research stations of other countries did not have an aircraft available. Severe blizzard conditions prevented aircraft landing in any case. Rogozov had no option but to perform an operation on himself.

The operation started at 02:00 local time on 1 May with the help of a driver and meteorologist, who provided instruments and held a mirror so Rogozov could observe areas not directly visible. Rogozov lay in a semi-reclining position, half-turned to his left side. A solution of 0.5% novocaine was used for local anesthesia of the abdominal wall. Rogozov made a 10–12 cm incision of the abdominal wall, but while opening the peritoneum he accidentally cut the cecum and had to suture it. Then he exposed the appendix. According to his report, the appendix was found to have a dark stain at its base, and Rogozov estimated it would have burst within a day. The appendix was resected and antibiotics were applied directly into the peritoneal cavity. General weakness and nausea developed about 30–40 minutes after the start of the operation so that short pauses for rest were repeatedly needed after that. By about 04:00 the operation was complete.

After the operation gradual improvement occurred in the signs of peritonitis and in the general condition of Rogozov. Body temperature returned to normal after five days, and the stitches were removed seven days after the operation. He resumed his regular duties in about two weeks.

The self-surgery, which was photographed by his colleagues, captured the imagination of the Soviet public at the time. In 1961 he was awarded the Order of the Red Banner of Labour. The incident resulted in a change of policy, and thereafter, extensive health checks were mandatory for personnel to be deployed on such expeditions.

Rogozov died in 2000, aged 66, in Saint Petersburg, Russia, from lung cancer.


The upper denture falls when the patient opens his mouth wide. This is due to:

  # The upper denture falls when the patient opens his mouth wide. This is due to:
A. Thick labial flange
B. Over extended borders
C. Thick distobuccal flange
D. Poor peripheral seal



The correct answer is C. Thick distobuccal flange

The thickness of distobuccal flange of maxillary denture must be adjusted to accommodate the ramus, coronoid process and the masseter. If the flange is too thick, the coronoid process will push the denture out of place during opening or lateral movements of mandible.

Posterior palatal seal is recorded when the head is bent at:

  # Posterior palatal seal is recorded when the head is bent at:
A. 15 degree
B. 30 degree
C. 45 degree
D. 60 degree



The correct answer is B. 30 degree.

In conventional method of recording posterior palatal seal, the patient is seated in an upright position. In fluid wax technique, posterior palatal seal is recorded when the head is bent at 30 degree.