Capsid Shapes

 # One of the principal capsid shapes is a 20-sided figure with 12 evenly spaced corners referred to as a(n) _____ capsid. 

A. Spiked

B. Complex

C. Icosahedral

D. Helical

E. Buckeyball

The correct answer is C. Icosahedral.

In geometry, an icosahedron (/ˌaɪkɒsəˈhiːdrən, -kə-, -koʊ-/ or /aɪˌkɒsəˈhiːdrən/) is a polyhedron with 20 faces. The name comes from Ancient Greek εἴκοσι (eíkosi) meaning "twenty" and from Ancient Greek ἕδρα (hédra) meaning "seat". The plural can be either "icosahedra" (/-drə/) or "icosahedrons".

Virus

 # Viruses have all the following except :

A. Definite shape

B. Metabolism

C. Genes

D. Ability to infect host cells

E. Ultramicroscopic size

The correct answer is B. Metabolism.

Viruses are non-living entities and as such do not inherently have their own metabolism. However, within the last decade, it has become clear that viruses dramatically modify cellular metabolism upon entry into a cell.

Viruses consist of nucleic acid (genetic material) surrounded by a capsid (protein coat). Most scientists consider viruses to be nonliving because they can't carry out the most basic processes of life. Viruses can't metabolize (break down) food to release energy (carry out respiration) or grow.

Endodontic Surgery should be avoided in

 # Endodontic Surgery should be avoided in:

A. Short rooted teeth

B. Teeth with periodontal disease

C. Lingual surface of mandibular molars

D. All of the above

The correct answer is D. All of the above.

Because of inaccessibility and difficulty to gain access to the surgical site through dense layers of bone, endodontic surgery should be avoided on lingual surfaces of molars or external oblique ridge of mandible. 

Immunoglobulin most commmon in Periodontitis

#Which immunoglobulin is most common in patients with periodontal disease?

A. IgA

B. IgD

C. lgG

D. lgE

E. IgM 

The correct answer is C. IgG. 

The presence of IgG in gingival crevicular

fluid is a product of actively secreting plasma cells stimulated by chronic plaque/calculus accumulation. 

The next abundant type is IgA, There is a negligible amount of lgM.

lg A predominates in saliva to agglutinate

bacteria so they are more easily swallowed

and evacuated from the oral cavity.

Lingual holding arch

# A mandibular lingual holding arch with loops mesial to each molar band is used in children for:

A. Correction

B. Regaining space

C. Space maintenance only

D. Correction of distally tilted molars 

 

The correct answer is B. Regaining space.

Normal passive mandibular lingual holding arch is used for space maintenance in mandible. This is  a preventive procedure.

Lingual arch with U loops mesial to each molar band is a modification of mandibular lingual arch. The loops are opened periodically and this can bring about distalization of molars by 1 to 2 mm. This is an interceptive procedure.

Primary source of anaerobic bacteria in diseased periodontal tissue

 # Which of the following is the primary source of anaerobic bacteria in diseased periodontal tissue?

A. Supragingival plaque

B. Blood

C. Subgingival plaque

D. Calculus

The correct answer is C. Subgingival plaque. 

Subgingival plaque is most likely to contain the anaerobic bacteria that cause periodontal disease.

Remember that although calculus is a secondary etiologic factor, the primary etiologic factor of periodontal disease is dental plaque.

All Ceramic Restorations

 # Which of the following is the BEST way to avoid porcelain failure in all-ceramic restorations?

A. Rounded angles of the preparation

B. Minimal occlusal forces

C. Porcelain is 3.5mm thick

D. Porcelain is not more than 0.5mm thick 

The correct answer is A. Rounded angles of the preparation.

All ceramic restorations should include rounded angles in the tooth preparation in order to reduce stress concentration along these areas. Sharp angles within tooth preparations are areas where stress is concentrated, and may cause fracturing.

Porcelain thickness is also an important factor in its fracture toughness. All porcelain crowns should have a minimum thickness of 1mm circumferentially and about 1.5mm along the occlusal/ incisal to

achieve strength (Not including the framework of the restoration).

Proper case selection and occlusal load analysis is also an important factor in preventing failure of an all ceramic restoration.