Four handed Dentistry

# When utilizing four-handed dentistry, the assistant should be positioned...
A. Higher than the dentist to facilitate visibility
B. Different positions depending on where the dentist is working
C. Lower than the dentist for ergonomic posturing
D. At the same height because they are a team

The correct answer is A. Higher than the dentist to facilitate visibility.

In four handed dentistry, the assistant
should sit close to the back of patient's
chair higher than the dentist to facilitate
visibility.

This position is suitable for better view of
the site, instruments and materials from the
mobile cart or instrument tray. It also allows you access to these materials without leaning or overextending your arms.

Assistant stools should be placed in a
position so that their eye level is 4 to 6
inches higher than the dentist's.

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Dental Anomaly Affecting Only posterior Teeth

# Each of the following dental anomalies is likely to affect anterior teeth EXCEPT one. Which is the EXCEPTION?
A. Concrescence
B. False microdontia
C. False macrodontia
D. Gemination
E. Dens-in-dente

The correct answer is A. Concresence.

Concrescence characteristics:
Involves the union of two or more teeth
through CEMENTUM ONLY.

Most common in the permanent molars.

It is different from fusion, because it
occurs following eruption and never
involves enamel and dentin.

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Life cycle of an Ameloblast - Amelogenesis

# In the life cycle of an ameloblast, there are cells that contain Tomes' processes. The cells described are in which of following stages?
A. Morphogenic
B. Maturative
C. Organizing
D. Secretory
E. Protective

The correct answer is D. Secretory.

Tomes' process are projections or
extensions of ameloblasts formed as the
ameloblast moves away from the
developing enamel matrix.

The ameloblasts secrete secretory granules
needed for the production enamel matrix
during this phase.

Ameloblasts are actively contributing to the
enamel matrix formation by combining the
secretory granules with the glycoprotein to
lay down enamel during the secretory
phase.

Presence of Tomes' processes is a
histological indicator of the secretory
phase.

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Serial Extraction

# In the mandibular arch where the canines often erupt before the premolars, ________ technique of serial extraction is followed.
A. Dewel’s
B. Modified Dewel’s
C. Tweed’s
D. Nance’s

The correct answer is: B. Modified Dewel's.

Tweed defines it as “the planned and sequential removal of the primary and permanent teeth to intercept and reduce dental crowding problems”.

The term “serial extraction” was coined by Kjellgren in 1929 and popularized by Nance (1940) who has been called the ‘father of serial extraction'.

Indications of serial extraction:

Indications

1. Class I malocclusions with anterior crowding space discrepancy of 10 mm more.

2. Lingual eruption of lateral incisors.

3. Midline shift of mandibular incisors due to displaced lateral incisors.

4. Premature loss of deciduous canine.

5. Abnormal canine root resorption.

6. Severe proclination of mandibular and maxillary interiors with associated crowding.

7. Ectopic eruption.

8. Ankylosis.

Contraindications

1. Mild to moderate crowding (about 8 mm or less)

2. Congenital absence of teeth providing space

3. Class II div 2 and Class III malocclusion

4. Spaced dentition

5. Extensive caries involving permanent first molars which cannot be conserved.

6. Open bite and deep bite

7. Cleft up and palate cases, etc

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