What is Fluoride bomb?

# The ‘FLUORIDE BOMBS’ is related to:
A. A fluoride  capsule with high ppm of fluoride varnish
B. A hypoplastic lesion on tooth seen in fluorosis areas
C. Undiagnosed hidden caries
D. Procedure to treat rampant caries

The correct answer is C. Undiagnosed hidden caries.

• Occult or hidden caries is used to describe such lesion which is not clinically diagnosed but detected only on radiographs.
• Occult lesions are seen with low caries rate which is suggestive of increased fluoride exposure.
• It is believed that increased fluoride exposure encourages remineralization and slows down the progress of the caries in the pit and fissure enamel while the cavitation continues in dentin, and the lesions become masked by a relatively intact enamel surface.
• These hidden lesions are called 'fluoride bombs' or fluoride syndrome.

# Calcium hydroxide is advocated as an inter appointment intracanal medication because of

# Calcium hydroxide is advocated as an inter appointment intracanal medication because of:
A. Its ability to dissolve necrotic tissue
B. Its antimicrobial property
C. Its ability to stimulate hard tissue formation
D. Its powerful bleaching effect

The correct  answer is B. Its antimicrobial property. 

Most studies report culture reversals during the interappointment period when active antibacterial dressing is not used in the root-canal system between appointments. The reversals are due to regrowth of residual bacteria or recontamination by bacterial leakage around the access cavity

dressing. 

Classical and well-controlled studies (Sundqvist’s group) evaluated the effect of various root-canal treatment procedures on the microbiota both qualitatively and quantitatively. They tested the effect of mechanical preparation, saline or sodium hypochlorite irrigation (0.5%, 5.0%, 5.0% with EDTA), the addition of ultrasonic activation to the irrigation and calcium hydroxide dressing; each addition to the chemical canal preparation improved the antibacterial effect, reducing residual bacteria further. They found the antibacterial action to reduce the number of bacteria from an initial range of 10^2–10^8 cells to 10^2–10^3 fewer cells after initial debridement, further reducing down to no recoverable cells (from the prepared part of the root-canal system) after interappointment dressing with calcium hydroxide.

Reference: Endodontics, 4th Edition, Kishor Gulabivala, Yuan-Ling Ng, Page no. 83

Initial dissolution of Tooth Substance by Acid

# In the carious process, the initial dissolution of the tooth substance by acid takes place in which of the following place?
A. Below the dentin Surface
B. Below the enamel surface
C. On the enamel surface
D. Towards the dentin

The correct answer is B. Below the Enamel Surface.

The top portion of the tooth remains intact and it's the subsurface which looses the minerals. This is the stage where it's called as incipient lesion. Once the top protion breaks, it's called a cavitated lesion.

Digestive System and Nutrition - MBBS BDS Entrance Examination

The correct answers are highlighted in green.

# Micelles are the bodies related to:
 A. Secretion of hormones
 B. Secretion of enzymes
 C. Absorption of minerals
 D. Absorption of fat

# Movements of circular muscles in the stomach is called
 A. Digestion
 B. Absorption
 C. Excretion
 D. Peristalsis

Sites of Various Metabolic Pathways

Sites	Metabolic Pathways
Mitochondria	Citric acid cycle Oxidative phosphorylation Fatty acid oxidation Electron transfer Synthesis of ketone bodies
Ribosomes	Protein Synthesis
Golgi Complex	Glycoprotein synthesis
Nucleolus	RNA Synthesis
Cytoplasm	Cholesterol synthesis Glycolysis Fatty acid synthesis Glycogenesis Glycogenolysis HMP shunt Gluconeogenesis
In both mitochondria and cytosol	Urea Cycle Gluconeogenesis

# Clotting factor common to extrinsic and intrinsic pathway is:

# Clotting factor common to extrinsic and intrinsic pathway is:
A. Factor II
B. Factor III
C. Factor V
D. Factor VII

The correct answer is C. Factor V.

Prothrombin activator that is formed in intrinsic and extrinsic pathways converts prothrombin

into thrombin in the presence of calcium (factor IV). 

Once formed thrombin initiates the formation of more thrombin molecules. The initially formed thrombin activates Factor V. Factor V in turn accelerates formation of both extrinsic and intrinsic prothrombin activator, which converts prothrombin into thrombin. This effect of thrombin is called positive feedback effect. 

# Acid etching is done to:

# Acid etching is done to:
A. Decrease microleakage
B. Decrease polymerization shrinkage
C. Decrease Coefficient of thermal expansion
D. Decrease porosity in restorative material

The correct answer is A. Decrease microleakage.

Acid-etching transforms the smooth enamel into an irregular surface  and increases its surface free energy. When a fluid resin-based material is applied to the irregular etched surface, the resin penetrates into the surface, aided by capillary action. Monomers in the material polymerize, and the material becomes interlocked with the enamel surface.The formation of resin microtags within the enamel surface is the fundamental mechanism of resin-enamel adhesion.

As measured in the laboratory, shear bond strengths of composite to phosphoric acid-etched enamel usually exceed 20 megapascals (MPa) and can range up to over 50 MPa, depending on the test method used. Such bond strengths provide adequate retention for a broad variety of procedures and prevent leakage around enamel margins of restorations.