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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Contraindication for an all ceramic crown

# Each of the following patient situations is

considered a contraindication for an all-

ceramic crown EXCEPT one. Which one is

the EXCEPTION?

A. Extensive wear of tooth structure or restorations

B. Previous history of ceramic crown fractures

C. Amalgam restorations with marginal breakdown

D. Severe bruxism

The correct answer is C. Amalgam restorations with marginal breakdown. 

A history of ceramic crown fractures and extensive wear of opposing tooth structure

or restorations suggests to the clinician

that a heavy occlusal load is present during

occlusion.

People who chew hard foods and brux

severely will place the all-ceramic crown

under strong occlusal forces that may

cause it to fracture or overly wear the

opposing teeth.

Extensive and faulty amalgam restorations

that are displayed or are not placed

esthetically can be better replaced with an

all-ceramic crown.

Amalgam restorations with marginal

leakage and/ or breakdown can be

replaced in the core build-up for the PFM crown.

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Loss of apical seat due to overinstrumentation

# Which method is the best to manage loss of apical seat due to over-instrumentation?
A. Increasing the file size and decreasing the file length
B. Prescribing analgesics and antibiotics
C. Filling with a gutta-percha cone that is larger
D. Using a chelating agent and packing with calcium hydroxide
E. Filling with a warm gutta-percha technique

The correct answer is A. Increasing the file size and decreasing the file length. 

When the apical seat is accidentally

removed, the ability to create a hermetic

seal at the apex is compromised.

In order to avoid this procedural error, a

shorter length of file should be used to

establish a correct working length.

The correction of working length will

eventually help re-establish apical seat, then adequate flaring of the apical portion of the canal can be done with the use of larger sized hand files.

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Highest failure risk in endodontic perforation

# Which of the following locations would a
perforation present the HIGHEST failure risk?
A. Furcation
B. Apical 1/3 of the root
C. Crown
D. Middle 1/3 of the root
E. Apex

The correct answer is A. Furcation.

The HIGHEST risk for endodontic failure is
the perforation through the furcation because it is most difficult to seal.
Perforations of the crown may be sealed
with the final restoration.
Perforations near the root apex can be
sealed during obturation.
Teeth with endodontic perforations may still be successful. Perforations are NOT a
guarantee of endodontic failure.

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