# To prevent sensitivity caused by acid etching and to protect pulp in deep cavities, which of the following should be used?

# To prevent sensitivity caused by acid etching and to protect pulp in deep cavities, which of the following should be used?
A. Calcium hydroxide liner
B. ZnO liner
C. Light cure GIC liner
D. Lining with varnish

The correct answer is A. calcium hydroxide liner

Deep caries excavation close to the pulp, which may result in either an undetected pulpal exposure or a visible pulpal exposure, should be covered with a calcium hydroxide liner that can stimulate formation of dentin bridges (reparative dentin) over the exposure.

For amalgam restorations, deep excavations not encroaching on the pulp should be covered with a glass-ionomer material that will contribute to thermal protection and provide mechanical protection from amalgam condensation forces at thicknesses of I to 1.5 mm or greater.

Bonding of Composite resin to tooth

# Bonding of composite resins to tooth structure is by: (KAR-01)
a) Covalent bond
b) Ionic bond
c) Mechanical
d) Vander waal forces

The correct answer is C. Mechanical

Bonding of composites to tooth structure occurs by micromechanical retention. Acid etching creates micro porosities into which the resin penetrates resulting in resin tag formation. These tags penetrate to a depth of 5 - 10 µm but their lengths are dependent on the enamel etching time.

Advantages of Dental Composite Resins:

# The main advantage of composites over unfilled direct filling resin is their: (KAR-97)
a) Higher solubility in saliva
b) Lower modulus of elasticity
c) Esthetic excellence
d) Lower thermal co-efficient of expansion

The correct answer is D. Lower coefficient of thermal expansion.

Advantages of composites over unfilled resins:

• Lower coefficient of thermal expansion
• Low polymerization shrinkage
• Low water absorption
• High abrasive resistance

Disadvantages of composites:

• Less color stability
• Less smooth finish than unfilled resins

Hyperplastic Tissue Management in Complete Dentures

# The most common reason why hyperplastic tissue is removed during the construction of a complete denture is that:
a) It interferes with the arrangement of the teeth
b) It is unaesthetic to construct a denture on a hyperplastic tissue
c) It interferes with the stability of the denture
d) All of the above

The correct answer is C. It interferes with the stability of the denture.

The most important reason for the treatment of hyperplastic tissue before the construction of complete or removable partial dentures is to provide a firm, stable base for the denture.