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.

# Iron content in 3M Nickel based steel crowns is:

# Iron content in 3M Nickel based steel crowns is: (MAN -01)
a) 20%
b) 40%
c) 60%
d) 10%


The correct answer is D. 10 %.

Composition of stainless steel crowns:
Stainless steel (18-8) austentic type of alloy is used. Eg.: Rocky mountain and unitek.
Iron -                 87%
Chromium - 17%
Nickel -         12%
Carbon -          0.08 - 1.15%

Nickel base crowns. Eg.: Iconel 600 and 3M crowns
Iron                     -  10%
Chromium -    16%
Nickel - 72%
others - 2%

# A gingival wall is difficult to obtain in primary molar when it extends too far gingivally in class II cavities because: (MAN-97)

# A gingival wall is difficult to obtain in primary molar when it extends too far gingivally in class II cavities because: (MAN-97)
a) Facial pulp horn may be exposed
b) Inclination of cervical enamel rods occlusally
c) Of marked cervical constriction
d) Prime contact is broad and flat


The correct answer is C. of marked cervical constriction.

Gingivally the enamel rods have an occlusal direction in primary teeth so bevel is not required as there will be no unsupported enamel rods. It is difficult to obtain gingival wall when lesion extends too far gingivally in primary molar due to the presence of marked cervical constriction.

# Dose adjustment of all of the following drugs will be required in patient with severe liver cirrhosis EXCEPT:

# Dose adjustment of all of the  following drugs will be required in a patient with severe liver cirrhosis EXCEPT:
a) Lorazepam
b) Theophylline
c) Paracetamol
d) Metronidazole


The correct answer is A. Lorazepam.

PHARMACOKINETICS
Most of the BZDS are metabolized in the liver to produce active products (thus long duration of action). Active metabolites may result in cumulative effects. After metabolism, these are conjugated
and are excreted via kidney. Estazolam, lorazepam, oxazepam, temazepam and triazolam are directly conjugated without metabolism to active products. These drugs are thus short-acting and do not
accumulate on repeated administration. Further these drugs can be safely administered in liver failure and in elderly because these are conjugated directly without undergoing metabolism in the liver.
(Mnemonics: @ TO-LET; Short-acting drugs are Triazolam, Oxazepam, Lorazepam, Estazolam and Temazepam,). Compounds with shorter half life are favored in patients with sleep-onset insomnia whereas longer acting BZDS are favored in patients with day time anxiety.

Adverse effects
Benzodiazepines are much safer than barbiturates (less chances of respiratory depression and coma) and also have less abuse potential. However, these drugs can also impair learning and memory
Flunitrazepam is a tasteless BZD and is implicated as a date rape drug due to its propensity to cause dose dependent amnesic effects.

Benzodiazepine Antagonist
Flumazenil is the substance that acts as competitive antagonist at BZD receptor. It blocks the depressant action of benzodiazepine, zolpidem and zaleplon as well as the convulsant action of inverse agonist (like B-carotene).  It is administered i.v. for the treatment of BZD poisoning (specitie antidote) and can also be used to reverse BZD anaesthesia.

# Of the following local anesthetics, which has intrinsic vasoconstrictive action? (MAN -97)

# Of the following local anesthetics, which has intrinsic vasoconstrictive action? (MAN -97)
a) Cocaine
b) Procaine
c) Xylocaine
d) Bupivacaine


The correct answer is : A. Cocaine

All local anaesthetics except cocaine are synthetic compounds and they are vasodilating in nature. Cocaine is a natural local anaesthetic agent and causes local vasoconstriction.

 (Cocaine increases the vasoconstrictive action of adrenaline. If LA with adrenaline is given risk of death is more in cocaine abusers. So they are known as  'walking time bombs.'


Which of the following is the preferred local anesthetic technique for hemophilics? (MAN -01)

# Which of the following is the preferred local anesthetic technique for hemophilics? (MAN -01)
a) Nerve block
b) Supraperiosteal
c) Intraligamentary
d) Field block


The correct answer is C. Intraligamentary.
 In hemophilics to avoid complications,  Intraligamentary  (an intraosseous technique) method of local infiltration technique is preferred. In this technique, the solution is deposited in depth of gingival sulcus. The needle should be inserted apically into the bone until resistance is met.

# Which of the following may least be used as an abutment: (PGI -2K)

# Which of the following may least be used as an abutment: (PGI -2K)
a) Tooth with minimum crown
b) Tooth with short tapered crown and conical roots
c) Rotated and tipped tooth
d) Pulp treated tooth

The correct answer is: B. b) Tooth with short tapered crown and conical roots

# Epitheloid cells are seen in all of the following except (MAN -02):

# Epitheloid cells are seen in all of the following except (MAN -02):
a) Tuberculosis
b) Granulation tissue
c) Syphilis
d) Sarcoidosis



The correct answer is : B. Granulation Tissue

Epitheloid cells are a collection of modified macrophages present in granuloma. Granulomas occur in Tuberculosis, Leprosy, syphilis, Actinomycosis, Sarcoidosis, etc.

# The wetting of an adherent surface by an adhesive is related to: (AIPG-01)

# The wetting of an adherent surface by an adhesive is related to:
(AIPG-01)
A. Surface texture of the adherent
B. Surface energy of the adherent
C. Nature of the adherent that is crystalline or amorphous
D. Surface tension of the adherent

The correct answer is B. Surface energy of the adherent.

The property of wetting and adhesions are directly related to surface energy of adhesives. Substances with low surface energy like teflon are often used to prevent the adhesion of films to a surface. Metals because of their high surface energy, interact vigorouslywith liquid adhesives.

The surface energy of many restorative materials is higher when compared to that of tooth. So, there is greater tendency for the surface and margins of restorations to accumulate debris. This property will explain the relatively high incidence of marginal caries seen around dental restorations.


What is Proportional Limit?

# The proportional limit is defined as:
A. The maximum stress in a structure
B. The minimum force required to cause a structure to break
C. The maximum stress that can be induced without permanent deformation
D. The maximum elongation under tension that
 can be measured before failure


The correct answer is C. The maximum stress that can be induced without permanent deformation.

Stresses above proportional limit cause plastic deformation. This stress is called yield strength or proof stress. It  is the greatest stress, produced in a material such that stress is directly proportional to the strain. 

Phillip's Science of Dental Materials, 12th ed. Page no 57.

Most Common reason for removal of Impacted Mandibular third molars:

# Most common reason for the removal of impacted mandibular third molars is:
 A. Referred pain
 B. Recurrent pericoronitis
 C. Chronic periodontal disease
 D. Orthodontic treatment


The correct answer is B. Recurrent Pericoronitis

Pericoronitis is an inflammatory lesion occurring around the impacted or partially erupted tooth. An incomplete eruption of the tooth provides a large stagnation area for food debris under the gingival flap. This becomes infected easily and results in inflammation of the pericoronal flap. It exhibits chronic inflammation for a long period. If the debris and bacteria are deeply entrapped, an abscess may form which is called a pericoronal abscess. It is a mixed infection and various bacteria of the dental plaque (particularly anaerobes) play a significant role in the development of pericoronitis.

Clinical Features: The mandibular third molar is the commonly involved tooth. Pain and swelling of the pericoronal tissue around the affected tooth, difficulty in chewing, and difficulty in opening the mouth are the usual complaints. The patient may be mildly ill with fever, malaise, and regional lymphadenopathy.

Management: Entrapped food debris must be removed. When the upper tooth is involved, it should be grounded or extracted if it is malposed. Radiograph helps in assessing the position of the involved tooth. If impacted, the tooth must be removed. And if it is in a favorable position, surgical removal of the pericoronal flap is advocated after acute symptoms subside. The administration of antibiotics helps to relieve the symptoms and prevents the spread of infection to the adjacent tissue spaces.

Ref: Shafer's Textbook of Oral Pathology, 7E, Page: 400

AIIMS MDS Nov 2007 MCQs - Part 2


# In lead poisoning, gingival discoloration presents as:
A. Blue black line
B. Yellow line
C. Grayish black line
D. Steel gray line

# Dilaceration occurs due to:
A. Trauma to the tooth germ during root development
B. Abnormal displacement of the tooth germ during root development
C. Abnormal displacement of enamel epithelium during tooth development
D. Abnormal displacement of ameloblasts during tooth development

AIIMS MDS Nov 2007 MCQs - Part 1



# Which one of the following is a junction of frontal,parietal, temporal and greater wing of sphenoid bone?
A. Pterion
B. Lambda
C. Vertex
D. Inion

# A non synovial joint with dense connective tissue between two bony surfaces is termed as:
A. Synchondrosis
B. Syndesmosis
C. Symphysis
D. Suture

Radiographically, driven snow appearance is seen with:

# Radiographically, driven snow appearance is seen with:
A. Adenomatoid odontogenic tumor
B. Calcifying odontogenic cyst
C. Calcifying epithelial odontogenic tumor
D. Keratocyst


The correct answer is C. Calcifying Epithelial Odontogenic Tumor

- Scattered flecks of calcification throughout the radiolucency has given rise to the descriptive term driven snow appearance.
- Lesion appears as diffuse or well circumscribed unilocular radiolucency.
- Combined radiolucency and radioopacity with irregular bony spicules producing honeycomb pattern
- Scattered flecks of calcification give driven snow appearance
- Sometimes, lesion is totally radiolucent and in association with unerupted tooth

Zones of Dentinal Caries

ZONES OF DENTINAL CARIES
ZONE 1 Normal Dentin
Zone 2 Subtransarent Dentin
  • Zone of demineralization (by acid from caries)
  • Damage to the odontoblastic process is evident.
  • However, no bacteria are found in the zone.
  • Stimulation of the dentin produces pain, and the dentin is capable of remineralization.
Zone 3 Transparent dentin
  • Softer than normal dentin
  • Further loss of mineral from the intertubular area.
  • Stimulation of this region produces pain. There are no bacteria present.
  • The collagen cross-linking remains intact in this zone, can serve as a template for remineralization.
  • The intact collagen of the intertubular dentin, and thus this region remains capable of self-repair, provided the pulp remains vital.
Zone 4 Turbid dentin
  • Turbid dentin is the zone of bacterial invasion 
  • Widening and distortion of the dentinal tubules which are filled with bacteria.
  • There is very little mineral present and the collagen in this zone is irreversibly denatured.
  • The dentin in this zone will not self-repair.
  • This zone cannot be remineralized and must be removed prior to restoration
Zone 5 Infected Dentin
  • The outermost zone, infected dentin, consists of decomposed dentin that is teeming with bacteria.
  • There is no recognizable structure to the dentin.
  • Absence of collagen and mineral content.
  • Great numbers of bacteria are dispersed in this granular material.
  • Removal of infected dentin is essential to sound, successful restorative procedures as well as prevention of spread of the infection

# Whenever the caries cone in enamel is larger or at least the same size as that in dentin, it is called as:

# Whenever the caries cone in enamel is larger or at least the same size as that in dentin, it is called as:
A. Residual caries
B. Recurrent caries
C. Forward caries
D. Backward caries


Forward Caries. Forward caries is where the caries cone in enamel is larger or at least the same size as that in dentin.

Backward Caries. When the spread of caries along the DEJ exceeds the caries in the contiguous enamel, caries extends into this enamel from the junction.

Ans is C: Forward caries (Ref: Sturdevant's Art and science of operative dentistry 4th ed., p 274)

# DPT vaccine does not provide immunity against:

# DPT vaccine does not provide immunity against:
A. Tetanus
B. Diphtheria
C. Polio
D. Whooping cough


The correct answer is C. Polio.

The vaccine DPT stands for Diphtheria, Pertusis (Whooping cough) and Tetanus. 

# I.V. Diazepam in a patient on a dental chair can cause: [AIIMS 2007 NOV]

# I.V. Diazepam in a patient on a dental chair can cause: [AIIMS 2007 NOV]
A. Tinel’s Sign
B. Verrill’s Sign
C. Bell’s sign
D. Coleman’s sign



The correct answer is B. Verrill's Sign.
Verrill's  sign has 3 Symptoms which indicate  the correct level after  diazepam sedation.
- 50% eyelid ptosis
- Blurring of vision
- Slurring of speech 
Verrill's Sign

# Tinel's Sign: Tinel sign was used earlier as an indicator of the start of the nerve regeneration. It is elicited by percussion over the divided nerve, which result in tingling sensation in part supplied by peripheral section.

# Coleman's sign: Seen in mandibular fractures. Ecchymosis in the lingual sulcus is pathognomic of mandibular fracture.

 # Bell's Sign: Bell's phenomenon (also known as the palpebral oculogyric reflex) is a medical sign that allows observers to notice an upward and outward movement of the eye, when an attempt is made to close the eyes. The upward movement of the eye is present in the majority of the population, and is a defensive mechanism. 

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