The best surface for a macrofilled composite resin is achieved by:

 # The best surface for a macrofilled composite resin is achieved by:

A. Allowing polymerization to occur against a mylar matrix

B. Use of a green stone

C. Use of an extra fine silicone carbide disc

D. Use of a white stone

The correct answer is A. Allowing polymerization to occur against a mylar matrix.

Finishing of composite resins is best done after 24 hours during which time the polymerization is complete. However, if a subsequent appointment is not desired finishing procedures can be started 15 minutes after curing. The initial contouring can be done with a knife or diamond stone. The final finishing is done with rubber impregnated abrasives or rubber cup with polishing pastes or aluminium oxide disks. The best finish is obtained when the composite is allowed to set against a matrix or mylar strip.

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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.

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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.

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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.

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