Retention of Dental Composite resins

# Dental composite resin restorations are retained by:
A. Cohesion
B. True bonding
C. Mechanical interlocking
D. Atomic forces

The correct answer is C. Mechanical interlocking.

- Surface irregularities are produced by acid etching enamel with 37% to 50% phosphoric acid.
- The primer flows into these irregularities and resin tags are formed providing mechanical interlocking providing micromechanical bonding.
- The microtags formed are 2 to 5 micrometers in length.
- Bond strength is in the range of 18 to 22 MPa.
- Composites increase resistance form by bonding and strengthening tooth structure.

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Fish net pattern in Pemphigus Vulgaris

# Fish Net pattern in pemphigus vulgaris is seen in which of the following tests?
a) Direct immunofluorescence
b) Tzanck smear
c) FNAC
d) Histopathology

The correct answer is A. Direct immunofluorescence.

Pemphigus vulgaris causes intraepithelial bullae formation and results in loss of cohesiveness or acantholysis. Due to this, clumps of epithelial cells are found lying free in the vesicular space, known as Tzanck cells. These changes are seen in cytological smears also known as the Tzanck smear or Tzanck test. The fluid in most vesicles has scarce inflammatory cell infiltration.

Direct Immunofluorescence predominantly demonstrates the presence of IgG in combination with IgM, IgA, C3. Direct Immunofluorescence reveals a typical fish net pattern or chicken wire pattern of IgG antibodies against desmoglein 1 or 3 even in the perilesional skin.

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Elevators on Exodontia

# Most of the elevators used in exodontias work on the principle of:
A. Class I lever
B. Class II lever
C. Class III lever
D. Wheel and axle

The correct answer is A. Class I lever

Most of the elevators used are class I or simple levers. The fulcrum (alveolar bone) is located between the applied force (hand of the operators) and the load or resistance (tooth).

Effort arm (distance between the fulcrum and the force applied) should be greater than resistance arm (distance between the fulcrum and the load or resistance i.e. Tooth).

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Rh hump is seen in:

# Rh hump is seen in which portion of a tooth?
A. Cementum
B. Enamel
C. Dentin
D. Alveolar bone

The correct answer is B. Enamel.

In Erythroblastosis fetalis, there is deposition of bilirubin pigment in the enamel and dentin of developing teeth giving them a green, brown or blue hue.

In some cases, enamel hypoplasia involving the incisal edges of anterior teeth and middle third of deciduous cuspid and first molar may be seen resulting in a characteristic ring like defect known as 'Rh hump'.

No treatment for tooth pigmentation is necessary since it affects the deciduous teeth and presents only a temporary cosmetic problem.

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