Elevators are instruments designed to:

# Elevators are instruments that are designed to:
A. Engage the tooth coronal to the cementoenamel junction
B. Retract the crestal gingiva before forceps are used
C. Reflect a full thickness flap before forceps are used
D. Engage the tooth apical to the cementoenamel junction

Elevators are instruments used to elevate
the tooth out of its socket.

Elevators are designed to engage the root
portion of the tooth below the
cementoenamel junction.

Elevators are inserted into the periodontal
ligament space, create more room for tooth
movement, and help elevate the tooth out of its socket.

Most undesirable property of sodium hypochlorite

# Which of the following is the most UNDESIRABLE property of sodium hypochlorite?
A. Tendency to bleach tooth structure
B. Reaction with chelating agents
C. Smell
D. Corrosiveness to endodontic files
E. Toxicity to vital tissue

The correct answer is E. Toxicity to vital tissue.

Sodium hypochlorite in undiluted or
excessive amounts is toxic to vital tissues
and can cause periapical tissue damage
and pain.
Sodium hypochlorite is a good disinfectant
that is used in dentistry as an endodontic
canal irrigant at a diluted concentrations.
Sodium hypochlorite is used often used to
disinfect gutta percha points prior to
placement and obturation of the canal.

First step in cavity preparation

# Which of the following describes the 1st step in cavity preparation according to G.V. Black?
A Retention form
B. Outline form
C. Resistance form
D. Convenience form

The correct answer is B. Outline form.

The 1st step in cavity preparation according
to G V Black is to establish the outline form.
The initial extension or the outline form of
the tooth preparation should be visualized
preoperatively by estimating the extent of
the defect, the preparation form requirements of the amalgam, and the need
for the adequate access to place amalgam
into the tooth.

G.V Blacks various steps of cavity preparation are:
- Establish outline form
- Obtain retention form
- Obtain resistance form
- Obtain convenience form

Least distance between tooth and implant:

# The implant should be positioned at least ____ away from natural tooth:
a) 0.5 mm
b) 1.0 mm
c) 1.5 mm
d) 2.0 mm

The correct answer is C. 1.5 mm.

When the implant is closer than 1.5 mm to an adjacent root of a tooth, the wedge-shaped vertical defect may become a horizontal defect, creating bone loss on the adjacent tooth root. 

Initial vertical bone loss around an implant during the first year of loading varies and ranges from 0.5 to more than 3 mm. this effect is utmost importance because the interseptal bone height in part determines the incidence of presence or absence of interdental papillae between the teeth or implants. As a result, an implant should be at least 1.5 mm from adjacent teeth whenever possible.

Natural tooth roots are often close than 1.5 mm to each other. Therefore the ideal mesiodistal implant size is usually less than the natural root dimension. Most often, the ideal implant diameters used to replace the average size anterior tooth correspond to a 4.2 mm implant for a central incisor and canine, and a 3 to 3.5 mm implant for a lateral incisor.

The two conditions that determine the ideal anterior tooth implant size in the mesiodistal dimension are:

• The ideal diameter most often corresponds to the width of the missing natural tooth, 2 mm below the CEJ.

• In addition, the implant diameter plus 1.5mm on each side should be equal to or less than the mesiodistal dimension between the two natural roots at the level of the crest of the residual ridge.

When implants are placed adjacent to each other, a minimum distance of 3 mm is suggested, especially when crestal bone is expected around the implants, to accommodate for eventual crestal bone loss and maintain interseptal bone levels.

The four conditions that determine the ideal implant size in the posterior maxilla are:

1. The implant dimension should correspond to the natural tooth (2 mm below the CEJ).

2. The implant should be at least 1.5 mm from the adjacent teeth.

3. The implant should be at least 3 mm from an adjacent implant.

4. The implant should be at least 4 mm in diameter.

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Denture cleaning powder

# Which of the following is a main ingredient of denture cleaning powder or tablets?
a) Hydrogen peroxides
b) Detergents
c) Sodium perborates
d) Alkaline compounds

The correct answer is C. Sodium Perborates

All the denture cleansing powder and tablets contain detergent, flavouring agent, alkaline compounds and sodium perborat e. The main component is sodium perborate. It decomposes in water to form a peroxide solution which inturn breaks down to liberate oxygen. It is this oxygen bubbles that remove the debris on the denture surfaces.

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Most common reason to repeat impression is:

# Most common reason to repeat impression is?
a) Improper positioning of tray
b) Too less or excess material
c) Voids that are irreparable
d) Improper mixing

The correct answer is A. Improper positioning of tray.

The most common reason to repeat an impression is improper positioning of the impression tray. If the tray position is improper, the flange of the impression which lies on the side of deviation will be excessively thick and the flange of the impression opposite to the deviation will be thin.

The other reasons are improper consistency, large voids, movement of the tray during setting and too little or too much impression material.

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Relieving mid-palatine area in complete dentures

# The purpose of relieving mid-palatine area in complete dentures is to prevent:
a) Pressure on palate
b) Midline fractures in dentures
c) Incorrect centric relation
d) Resorption of bone

The correct answer is A. Pressure on palate.

Mid palatine raphe is the median suture area covered by a thin submucousa and the mucosa layer is practically in contact with the underlying bone. For the reason the soft tissue covering the median palatal sutures is non resilient and may need to be relived to avoid trauma from the denture base.

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