Composites vs unfilled direct filling resin

# 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 (filled resins) over unfilled resins are lower co-efficient of thermal expansion. Low polymerization shrinkage, low water absorption and high abrasive resistance.

On the other hand, composites have less colour stability and do not take the smooth finish as that of unfilled resins.

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Endosonics utilizes which instrument

# Endosonics utilizes which instrument? (AIPG-94)
a) H file
b) Reamers
c) K file
d) Endo box

The correct answer is C. K file

Ultrasonic and sonic instruments are used for cleaning and shaping root canals.

The ultrasonic instrument contains a magentostrictive hand piece which hold a K-file or diamond file. It is operated at 20000 - 25000/sec.

The sonic instruments operate at 1500 - 6500 cycles/min (25-110/sec). Ultrasonic system uses sodium hypochlorite as irrigant, whereas the sonic system uses water as an irrigant.

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Enamel bevel on facial side

# Which of the following is the term to describe the enamel bevel placed on the facial side of a class IV preparation?
A. A conventional bevel
B. A retentive bevel
C. An esthetic bevel
D. None of the above

The correct answer is C. An esthetic bevel.

The enamel bevel placed on the facial side
or surface of a class IV preparation is an
esthetic bevel (Infinity bevel).

Esthetic bevels are typically placed at 60 degrees. This bevel is placed to remove or mask thel ine of demarcation between the restorative material and the tooth structure.

If NO bevel is placed, a visible line can be
seen at the restorative-tooth interface
making the restoration unaesthetic for the
patient.

Placement of this esthetic bevel also makes the restoration conservative, increases the resin bond strength and decreases the chances of fracture.

Retentive bevels are typically found around
the margins of a class V restoration.

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Composite resin restorations

# Composite resin restorations...
A. Have a thermal coefficient of expansion similar
to amalgam
B. Release fluoride
C. Can be placed and finished at the same appointment
D. Chemically bond to dentin

The correct answer is C. Can be placed and finished at the same appointment. 

Composite restorations are restorative

materials popularly used because of its:

 - High esthetic value

- Ease of manipulation

- Durability

Glass lonomer cement is a restorative

material that:

- Releases fluoride into surrounding tooth

structure

- Chemically bonds to tooth structure

- Is less resistant to wear than composite

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