Aiims 1 Expl

8/18/2019 Aiims 1 Expl

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Mock AIIMS 1 – Target AIIMS Nov 2015

Ans. 3.

Tributaries of cavernous sinus:- Superior ophthalmic vein.

- A branch from the inferior ophthalmic vein (or the whole vessel).

- Superficial middle cerebral vein.

-

Inferior cerebral veins.- Sphenoparietal sinus.

- Central retinal vein.

- Frontal tributary of the middle meningeal sometimes drain to it.

Ans.4. The nucleus from which most facial motor fibres are derived lies deep in the reticular formation of the caudal part of the

pons, posterior to the dorsal trapezoid nucleus and ventromedial to the spinal tract nucleus of the trigeminal nerve.

Ans.5.Small non polar molecules (including O2 and N2) and small uncharged polar molecules such as CO2 diffuse across the lipid

membranes of the cell.

Ans.6.In resting muscle, Troponin is first is tightly bound to actin and tropomyosin Covers the sites where myosin heads bind to

actin.

Ans.7.

In general, touch is associated with the ventral spinothalamic tract where as pain and temperature are associated with the

lateral spinothalamic tract.

Ans.8.The blood pressure measured by the sphignomanometer is higher than the intra arterial pressure because cuff pressure isdissipated by the tissues between the cuff and the artery.

Ans.9.

Vitamin K denotes a group of lipophillic, and hydrophobic, vitamins that are needed for the posttranslational modification ofcertain proteins mostly required for blood coagulation.

Ans.10.

Muscle glycogen cannot contribute directly to plasma glucose since muscle lacks glucose-6-phosphatase.

Ans.12.An okazaki fragment is a relatively short fragment of DNA (with an RNA primer at 5` terminus) created on the lagging

strand during RNA replication.

Ans.13.Extracellular matrix comprises of interstitial matrix and basement membrane. Degradation of collagen and other extracellular

matrix proteins is achieved by a family of matrix metalloproteinases, which are dependent on zinc ions for their activity.

Ans.14.Delayed prolonged leakage-

1. After 2 to 12 hours.

2. Involved venules as well as capillaries.3. Mild to moderate thermal injury, radiation, bacteria.

4. Mechanism unclear-may be due to the direct effect of the injuring agent leading to delayed endothelial cell damage.

Ans.15.Organisms are not equally susceptible against various antiseptics descending order of resistance to antiseptics and


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disinfectants is as follows-

1. Prions- least susceptible.2. Coccidia.

3. Spores.

4. Mycobacteria.

5.

cysts6. Small non enveloped virus.

7. Trophozooites.

8. Gram negative bacteria(non sporulating)

9. Fungi.

10. Large non enveloped viruses.

11. Gram positive bacteria.

12. Lipid enveloped viruses- most susceptible.

Ans.17.Staphylococci are hardy non-spore forming, ubiquitous bacteria and are present in air, fomites and dust or as normal flora of

humans and animals. They are resistant to heat and drying and may be recovered from non-physiologic environments weeksto months after inoculation. These organisms are gram positive and grow in clusters, aerobically or as facultative anaerobes.

Ans.18.

Measles virus is the member of the genus morbillevirus. It is closely related to the viruses causing canine and porcine

distemper, rinderpest of cattle, and peste des petits ruminants of goats and sheep. There is only one antigenic type- measles

virions are pleomorphic spherical structures having a diameter of 100 to 250 nanometer.

Ans.20.Cytochrome P-450 is not a reaction. It is the enzyme system involved in detoxification.

Ans.21.The safety of a drug depends on by what factor the dose producing desirable affect is separated from the dose eliciting toxic

effects. For finding out the margin of safety, we must calculate the medial lethal dose and medial effective dose of the drug

and then express their ratio. Such an expression is called as therapeutic index.

Ans.22.

Early phase II

1. In 20 to 200 patients.

2. Done in patients with diseases.

3. Done by single blind methods.4. Done to establish a dose range.

5. Done to see the potential therapeutic benefits and side effects.

Late phase II.1. On a larger number of patients.

2. Done by double blind method.

3. Done to ensure safety and efficacy of the new drug.

4. Done to compare the data with the standard drug.

Ans.23.Doxycycline with its longer half-life and lack of nephrotoxicity (biliary excretion) is a popular choice for patients with pre-

existing renal disease.

Ans.25.Coarctation of the aorta may be a feature of Turner (XO) syndrome and is associated with bicuspid aortic valve in over 70%of patients.

Ans.28.


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• Imatinib is a drug used to treat certain types of cancer. It is currently marketed by Novartis as Gleevec (USA) or

Glivec (Europe/Australia) as its mesylate salt, imatinib mesilate (INN). It was originally coded during development

as CGP 57148B or STI-571 (These terms are used in early preclinical publications). It is used in treating chronic

myelogenous leukemia (CML), gastrointestinal stromal tumors (GISTs) and a number of other malignancies.

• It is the first member of new class of agents that act by inhibiting particular tyrosine kinase enzymes, instead of non-

specifically inhibiting rapidly dividing cells.

Ans.29.

Non-absorbable sutures

1. Silk.2. Linen.

3. Surgical steel.

4. Nylon.

5. Polyester.

6. Polybutester.

7. Polypropylene.

Ans.30.

Abbe- Estlander operation is the grafting of a flap of tissue from one lip of the oral cavity to the other lip to correct a defectusing a pedicle with an arterial supply.

Ans.31.The landmarks are-

1. Inferior portion of the cartilaginous canal – Conley’s pointer.

2. Upper border of posterior belly of digastric.

Inferior belly is not in the immediate vicinity to be used as a landmark.

Ans.32.MCV of 100 points towards macrocytic anemia. So the first option would be to rule out of a B 12 deficiency before giving an

antifungal or undertaking surgery. This patient would of course be suffering from thiamine deficiency but manifestations of

thiamine deficiency are different.

Ans.33.The common complications of hemithyroidectomy are-

1. Hemorrhage.

2. Respiratory obstruction.

3. RLN palsy.

4. Thyroid insuffiice.

5. Thyroid crises.6. Wound infection.

7. Hyperplastic or keloid scar.

8. Stictch granuloma.

Ans.34.

The morphologic variants of thyroid carcinoma and their appropriate frequencies are as follows:

•

Papillary carcinoma-75 to 85%.

• Follicular carcinoma-10 to 20%.

• Medullary carcinoma-5%.

• Anaplastic carcinoma-Rare.

Ans.35.The major anatomic landmark in the neck is the platysma muscle. This thin, broad muscle lies just beneath the skin and

covers the entire anterior triangle and anteroinferior aspect of the posterior triangle. Wounds that fail to penetrate the

platysma are considered superficial and do not warrant extensive evaluation. Wounds that do penetrate the platysma mandate


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hospital admission and further evaluation.

Ans. 36.“The physical change from the sol to gel, and vice versa, is induced by a temperature change. However, the hydrocolloid gel

does not return to the sol at the same temperature at which it solidified. The gel must be heated to a higher temperature

known as liquefaction temperature (70 to 100 C) to return it to the sol condition”.

Remember:

• The manipulation includes liquefying the gel, placing it in impression tray, tempering it to lower tolerable

temperature and maintaining it in its fluid state to capture the details of oral structures.

• In mouth material is cooled below mouth temp to ensure gelation.

• Propylene glycol can be added to water to obtain a liquifaction temperature to 100C.

• After agar hydrocolloid material has been liquefied it may stored in the sol condition at 65C.

• Maximum tolerable temperature of oral cavity is 55C.• Tempering is done in tempering container of 45C for time of 3 to 10 mins.

• Syringe material is never tempered.

• Gelation is accelerated by circulating cool water (18C to 21C) through the tray for 3 to 5 mins.• Material transforms from sol into a gel between 37C and 50C.

Ans. 37.

• Delayed expansion is probably caused by internal pressure entered by hydrogen gas that is one of the corrosion

products between Zinc in amalgam and incorporated moisture.

• The large expansion begins 4 to 5 days following condensation.

• Thus a patient who complains of pain 1 day after a restoration is placed cannot be suffering from the effects of

delayed expansion caused by incorporation of moisture into the setting amalgam.• Delayed expansion of amalgam often causes intense pain.

• It is assumed that when an expansion of this magnitude occurs, the restoration may become wedged so tightly against

cavity walls that a pressure towards the pulp chamber results.• Such pain may be experienced 10 to 12 days after the insertion of the restoration.

Ans. 38.

•“The absence of the corrosion susceptible γ2 phase in the microstructure of high-copper amalgam is assumed to be theprinciple factor responsible for the superior resistance of these alloys to marginal breakdown”

• Above lines make it clear that creep is related directly to presence of2 phase, which is present mainly in low copper

alloys and eliminated in high copper alloys like admix alloys and single composition alloys. Therefore creep value is

highest in low copper amalgam alloy.

Comparison of the Compressive Strengths and the Creep of Low-copper-silver-tin and High-copper Amalgams.

Amalgam Compressive C.s In 7 Days Creep % Tensile Strength –

Strength [Mpa] 24 Hours.

In 1 HourLow Copper 145 343 2.0 60

Admix 137 431 0.4 48

Single composition 262 510 0.13 64

• Many of high copper amalgams have creep rates of 0.4%

• Creep value of low-copper amalgam range from 0.8 % and 8%

• High copper amalgams have much lower creep values even less than 1%• There are no evident data available that suggest that reducing the creep value below approximately 1% influences

marginal breakdown.

Ans. 39.

Cement Anticariogenic effect Translucency Tooth Bonding PulpalirritationPolycarboxylate Yes- mild Absent Yes Mild

Resin cement No Absent No Moderate

Silicate Yes Present No Severe


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Glass ionomer Yes Present Yes Mild to moderate.

From the above table it is clear that the answer is glass ionomer cement.

Ans. 41.“Speckled leukoplakia is associated with a higher malignant transformation rate with up to two thirds of the cases in some

series showing epithelial dysplasia or carcinoma.”Precancerous lesions are:

- Leukoplakia and erythroplakia

- Lichen planus

- Syphilis and submucous fibrosis

- Oral hairy leukoplakia

• Evidence of pre-malignant potential, abnormal keratinization and dysplasia has not been seen in hairy leukoplakia.

• White sponge nevus is a rare benign and asymptomatic autosomal dominant disorder.

• Leukoplakia has been regarded as the most common presentation of oral cancerThus from the above text lines, it is clear that leukoplakias is most common presentation of oral cancer so rule out

options B and C as wrong.

Therefore we are left with only options speckled leukoplakia and hairy leukoplakia, of which speckled leukoplakia is theanswer of choice.

Ans. 42.

Under the clinical features of lateral periodontal cyst, the text mentions:

• “The location of the lesion was extremely limited in this study. 67 percent of cases were in mandibular bicuspid /

cuspid incisor area while 33 percent were in the maxillary lateral incisor area. Lesions were found at no other sites

and this has also been the experience of most other investigators”

Ans. 43.• “A second characteristic clinical feature of osteogenesis imperfecta is the occurrence of pale blue sclera”.

• The sclera are abnormally thin and for this reason the pigmented choroid shows through and produces bluish color.• Osteopetrosis, fetal rickets, turner syndrome, paget’s disease marfan syndrome, ehlers danlos syndrome as well as

normal infants may show the presence of blue sclera.

• The chief clinical characteristic of the condition is the extreme fragility and porosity of the bones with an attendant

proneness to fracture.• The fractures heal normally but the new bone is of a similar weak or defective quality.

• Also remember that when the condition is associated with Type-I dentinogenesis imperfecta, Opalescent hue of the

dentin is seen in the affected dentition.

Ans. 44.“The permanent maxillary lateral incisors are the teeth most frequently involved and in majority of cases, the dense in denteappear to represent simply an accentuation in the development of the lingual pit”

Ans.45SLE is characterized typically by a non erosive arthritis (erosions are rare). All other options mentioned in the question many

have an erosive picture.

Diagnostic criteria for arthiritis in SLE include:

Non erosive arthritis involving two or more peripheral joints characterized by tenderness, swelling or effusion.

Ans. 46.“Acinic cell carcinoma has been reported occurring chiefly in the parotids with more than 80 percent of the cases occurring

in the parotid gland”

ACINIC CELL CARCINOMA• It does occur occasionally in the other major glands and in the accessory intra oral glands.

• The most common intra oral sites are the lips and buccal mucosa.

• The acinic cell carcinoma occurs predominantly in persons in middle age or somewhat older. The mean age being 44

years.


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• Women were affected more than men (3:2).

Ans. 47.“Cavitation at the base of a pit can be sometimes detected tactilely as softness or by the binding of the tip of the explorer”

“Porous enamel appears chalky or opaque when dried with compressed air”- the two statements support the answer.

Also remember:1. Proximal caries in posterior teeth are detected most commonly by bite-wing radiographs.

2. Proximal caries in anterior teeth are detected most commonly by transillumination.

3. Peri-apical radiographs are used for the diagnosis of peri-apical pathologies.

Ans. 48.

ANEURYSMAL BONE CYST:• The radiographic picture of the lesion is often distinctive.

• The bone is expanded, appears cystic with a honey-comb or soap bubble appearance in many cases and is

eccentrically ballooned.• The cortical bone may be destroyed and a periosteal reaction may be evident.

GIANT CELL TUMOR:• In edentulous areas, the peripheral giant cell granuloma characteristically exhibits superficial erosions of the bone

with pathognomonic peripheral cuffing of the bone on the X-ray.

• When the tumor occurs in area in which teeth are present, superficial destruction of the alveolar margins or crest is

present. Thus it is eccentric in nature.

FIBROUS CORTICAL DEFECT:

Causes destruction of cortical plates and is eccentric in nature.

SIMPLE BONE CYST:It seldom causes displacement of teeth and in many instances the lamina dura may be intact. Thus it is the lesion which is

least likely to be eccentric in nature.

Ans. 49.Renal osteodystrophy may produce a Rugger jersey appearance in lateral X-rays of the spine due to alternating bands of

increased and decreased bone density.Common X-ray features of renal osteodystrophy:

- Widened and irregular epiphyseal plates

- Displacement of epiphysis or epiphseolysis

- Osteosclerosis and rugger jersey appearance of spine.

Renal osteodystrophy is a bone disease seen in patients with secondary hyperparathyroidism and renal failure. Thisprimarily includes

1. Rickets or osteomalacia

2. Osteitis fibrosa cysticaBiochemical parameters include:

1. Decreased serum calcium, urinary calcium & phosphate.

2. Increased serum phosphate, Alkaline phosphatase and PTH.

Ans. 50.

TREATMENT OF OSTEOSARCOMA• In the case of long bone involvement, amputation is the primary requisite.

• Neoplasms at other sites must be treated by radical resection.

• Primary X-ray radiation is of no value.• More recently, adjuvant chemotherapy with surgery, including the resection of pulmonary metastasis has appeared to

offer promise of increased survival from this disease.Also, Ewings’ sarcoma and Retinoblastoma are radio sensitive tumor.

Even Neuroblastoma is a radioresistant tumor, but the best answer here is Osteosarcoma.


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Ans. 51.

• Infective endocarditis is most commonly caused by alpha hemolytic streptococci- S.viridans.• Non-streptococcal organisms found in the periodontal pocket have been increasingly implicated and include

E.corrodens, A.actinomycetemcomitans, Capnocytophaga and Lactobacillus species.

• Endocarditis prophylaxis is recommended in:

A. High risk patients:1. Previous history of infective endocarditis

2. Prosthetic heart valves

3. Major congenital heart diseases: Fallot’s tetralogy, transposition of great vessels, single ventricular states.

B. Moderate risk patients:

1. Acquired ventricular diseases or dysfunctions

2. Other congenital heart malformations.

3. Hypertrophic cardiomyopathy

4. Mitral valve prolapse with valvular regurgitation, thickened leaflets or both.

Ans. 52.

Le-fort II Fracture: Kapoor 2nd /289- “Patients present with bilateral circumorbital ecchymosis and bilateral subconjunctival haemorrhage confined to

medial half of eye.”

Le-fort III Fracture: (Ref. Malik/Page 330)- Bilateral circumorbital/Periorbital ecchymosis and gross edema “Racoon eyes’. Gross circumorbital edema will

prevent eyes from opening.’

- Bilateral subconjunctival haemorrhage, where posterior limit will not be seen, when patient is asked to lookmedically.

Naso ethmoidal Fractures (Ref. Malik/Page 347)

- “Subcutaneous emphysema may be present”

Thus from above text, subconjunctival ecchymosis is present in all the options except Le Fort – I Fractures.

Ans. 53.

- Face-bow is used to establish a plane of reference, axis orbital plane. To establish it we must have a 3rd reference

point. This 3rd point is marked on the right side of the nose 2 and 1/8 inches from the incisal edges of a centralincisor tooth or it is determined by locating the inferior border of orbit on the right side.

- A face-bow may be used to transfer a comparable radius from arbitrary reference points, or it may be designed so that

the transfer can be made from hinge axis points. The latter type of transfer requires that a hinge-bow attached to the

mandible be used initially to determine the hinge axis points, to which the face-bow is then adjusted for making the

hinge axis transfer.

- A face bow transfer for maxillary cast, which is oriented to the axis or bital plane to suitable articulator, is anuncomplicated procedure. The Hanau series, all 96 H2-0 models, the whip-mix articulator and the Dentatus Model

ARH will accept this transfer. The Hanau earpiece face bow models 153 and 158, the Hanau facia face-bow 32, -2

SM, and the Dentatus face bow type AEB incorporate the infraorbital plane to the articulator. None of these are hinge

axis bows but are used instead at an arbitrary point.

Ans. 54Modified ridge lap pontic:

- They are designed to reduce the tissue contact.

- Satisfies both esthetics and hygiene.

- Tissue contact is limited to the buccal surface of the ridge crest.

- It has a ‘T’ shaped contact.

- The vertical arm of the T ends at the crest of the ridge.

- The horizontal arms form the contact along the buccal surface of the ridge.- Recommended in maxillary anterior and posterior regions.

- Modified ridge lap with no embrasures is recommended in mandibular anterior areas with extensive ridge resorption.

As maxillary canine is located in naturally asthetic area for which modified ridge lap is pontic of choice.


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Ans. 55.

• The correctly placed posterior palatal seal will not impinge upon the nondisplaceable tissues of the hard palate, norwill it limit the muscular movements of the soft palate. It will however, create a partial vaccum beneath the maxillary

denture. This partial vaccum is activated only when horizontal or tipping forces are directed against the denture base.

• The duration of time that a partial vaccum acts on the tissues is extremely small and consequently little or no

irreversible alterations to the underlying mucosa will take place. Remember:

- Posterior palatal seal is primary retentive area for maxillary dentures.

- Methods used to mark the post dam area are:

• Conventional method.

• Fluid wax technique

• Arbitrary scraping of master cast

• Extended palatal technique.

Ans.56.- All ceramic restorations are given in aesthetic areas.

- All ceramic restoration requires shoulder as one of its finish line which requires excessive tooth reduction.- In young children the pulp horns are wide and high and there are chances of exposure of pulp due to excessive

reduction for all ceramic restoration.- Also thickness of enamel and dentin is less in deciduous teeth.

Ans. 57.

- Epulis fissuratum is a soft tissue reaction that appears in the sulcular region due to overextension of the denture

flanges. It is commonly seen in immediate denture cases where rapid ridge resorption occurs.

- It does not require any special treatment, shortening and smoothening the denture border is sufficient.

Combination syndrome- It is seen in patients wearing a maxillary complete denture opposing mandibular distal extension prosthesis.

- The groups of complications in this syndrome are interlinked to each other.- In this syndrome there is resorption of maxillary ridge and the formation of flabby tissue with epulis fissuratum.

Ans. 58.

Steps in major connector fabrication:Step 1: Outline of primary stress bearing areas.

Step 2: Outline of non bearing areas

Step 3: Outline of connector areas

Step 4: Selection of connector type

Step 5: Unification

Ans. 59.“The average depth of corrosion for most amalgam alloys is 100 to 500 um”

Let us consider each option one by one.

1. Can extend upto a depth of 100-500 µm:

“The average depth of corrosion for most amalgam alloys is 100 to 500 µm.”

2. Decreases if tin content of alloy increases:

- The presence of small amounts of tin, silver and copper that may dissolve in various amalgam phases has a great

influence on their corrosion resistance.- The higher the tin concentration of Ag2Hg3, the lower is corrosion resistance.

- The presence of relatively high % of tin in low-copper alloys reduces the corrosion resistance of their γ1 phase so

that it is lower than phase. This is not true for high copper amalgams.

3. Is promoted by phase of alloy particles:

Electrochemical measurements on pure phases have shown that the Ag2Hg3 phase has the highest corrosion

resistance, followed by Ag3S1, Ag3Cu2, Cu3Sn, Cu6Sn5 and Sn7-8 Hg.

4. Is resisted most by copper-tin phase in high copper amalgams:


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- The eta phase formed with high-copper alloys is not an interconnected phase such as the phase, and it has

better corrosion resistance.- However is the least corrosion-resistant phase in high copper amalgams and a corrosion product,

CuCl2.3Cu(OH)2 has been associated with storage of amalgams in synthetic saliva.

- Phosphate buffer solution inhibits the corrosion process; thus saliva may provide some protection of dental

amalgams from corrosion.

- Surface tarnish of low copper amalgams is more associated with than γ1 whereas in high copper amalgams

surface tarnish is related to the copper rich phases n and silver- copper eutectic.

Ans. 60.“Primary resistance form may be defined as that shape and placement of the preparation walls that best enable both the

restoration and the tooth to withstand, without fracture, masticatory forces delivered principally in the long axis of the tooth.”Although you have revised the above definition ‘n’ number of times, there are many students who will mark option D, as

an answer. This can happen due to confusion caused due to fear of entrance exam. The key is to remain calm in exams and

male less number of mistakes.

Ans. 61.

• The resistance form of the restorative material [Amalgam] can be enhanced by using the gingival marginal trimmer to

bevel or round the axio-pulpal line angle.• This increases the bulk and decreases the stress concentration within the restorative material.

Ans. 62.- Cutting instruments have formulas describing the dimensions and angle of the working end.

- These are placed on the handle using a code of three or four numbers separated by dashes or spaces.- The first number indicates the width of the blade or primary cutting edge in tenths of a millimeter.

- The second number of four number code indicates the primary cutting edge angle, measured from a line parallel to the

long axis of the instrument handle in clockwise centigrade.

- The third number indicates the blade length in millimeters.

- The fourth number indicates the blade angle relative to the long axis of the handle in clockwise centigrade.

Angle former and gingival marginal trimmer are the instruments that have four digit formulas.

Ans. 63.

“The distance between holes is equal to the distance from the center of one tooth to the center of the adjacent tooth, measuredat the level of gingival tissue”.Generally, this is approximately ¼ inch (6.3 mm)

- If the distance between holes is excessive, the dam material wrinkles between the teeth.- Conversely, too little distance between holes causes the dam to stretch, resulting in space around the teeth and

leakage.

- When the distance is correct, the dam intimately adapts to the teeth and covers and slightly retracts the interdental

tissue.

- When rubber dam is applied to the maxillary teeth, the first holes punched are for the central incisors. These holes

are positioned approximately 1 inch (25mm) from the superior border of dam providing sufficient material to cover

upper lip.

- For mandibular teeth the first hole punched is for the posterior anchor teeth that is to receive the retainer.

Ans. 64.• “To relieve this (of acute alveolar abscess) constant pain, one should establish drainage through the root canalpreferably, and through the soft tissue and bone, if necessary.

• “The value of test cavity in treating teeth with acute alveolar abscess is two fold. First, it tests for any remaining vital

pulp that could require anesthesia and second, it initiates emergency therapy quickly, because the pulp chamber can

be penetrated painlessly without delay, waiting for anesthesia to take effect.

• Leaving the tooth open for drainage, reduces the possibility of continued pain and swelling.

Ans. 65.

• Superoxol is 30% solution of Hydrogen peroxide by weight and 100% by volume in pure distilled water.


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• It is stored in a light proof, amber colored bottle, away from heat.

• In a refrigerated, sealed container it can be stored for approximately 3 to 4 months.• It has an ischaemic effect on the skin and the mucous membrane that resembles a chemical burn.

• It is especially painful, if it comes in contact with the nail bed or the soft tissues under the finger nail.

• The amount needed for the bleaching operation is about 1 to 2 ml, dispensed in a clean dappendish.

• For bleaching endodontically treated teeth, the solution can be used alone or mixed with sodium perborate into apaste- a technique called as Walking Bleach.

• When placed into the pulp chamber the mixture oxidizes slowly and discolors the stain over a period of time.

Ans. 66. Endodontic treatment can be divided into three main phases:

1. Biomechanical preparation of the root canal

2. Disinfection of the canal

3. Obturation of the prepared canal.• The initial step for cleaning and shaping the root canal is proper access to the chamber that leads to a straight line

penetration of the root canal orifices.

• The next step is exploration of the canal, extirpation of the remaining pulpal tissue or gross debridement ofnecrotic pulp tissue and the verification of the instrument length.

• This step is followed by proper instrumentation, copious irrigation and disinfection of the root canal.• Obturation usually completes the procedure.

The principle aim of access opening is thus to obtain a straight line access to the apex.

Ans. 67.

• If the patient has a medical history of a Cardiac pacemaker, electric pulp testing is contraindicated as it may interfere

with the electrical activity of the pacemaker.• EPT uses electrical excitation to stimulate the A-delta nociceptor sensory fibres within the pulp.

• Teeth that temporarily or permanently lose their sensory function, as after trauma or Orthognathic surgery are

generally non-responsive to EPT.• False positive results may be obtained in necrotic pulps.

• False negative response may occur with pre-medications, alcohol, immature teeth, trauma, poor contact with tooth,

inadequate media and partial necrosis.

• In initial few days after an injury, a temporary paresthesia of the nerves may occur and make them unresponsive totesting. If the pulp retains its vitality, it will respond within normal limits after 30 to 60 days.

Ans. 68.

“Blomtof has shown that milk preserves the vitality of periodontal ligament longer than saliva, 6 hours versus 2 hours

respectively”• Once the tooth has been avulsed, effort should be made to preserve the vitality of the PDL.

• The avulsed tooth should be immediately rinsed in water and replanted into the socket by the patient.

• The best storage medium for storage of the avulsed tooth, for maintaining the vitality of the PDL is the tooth socket.• The second order of preference is to rinse the tooth in water and submerge it in a container of milk, with the patient

instructed to report to the dentist immediately with the tooth.

• The next option is to place the tooth in the buccal vestibule.

• The least preferable method is to rinse the tooth and place it in a cup of water and have it replanted by the dentist

immediately.

• Another preferable medium is HBSS- Hanks Balanced Salt Solution, which consists of NaCl, KCl and glucose.

Ans. 69.

• “Greater the intake and the frequency of consumption of the cariogenic food, greater the susceptibility to decay.Longer the oral clearance time, greater the occurrence of decay”

• Demineralization of tooth starts at a particular pH known as the Critical pH, which is usually 5.5 to 5.7• This pH is depicted in the form of a curve is called as the Stephan curve- proposed by Stephan R.M- 1940.

• From the curve it can be depicted that increased frequency of sugar intake causes the level of decreased pH, 5.5-5.7 to

be maintained for a longer period of time.


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• This can result in the colonization of bacteria and create favorable conditions for the occurrence of caries.

• Also remember that the pH of the oral cavity falls rapidly after a Sucrose rinse and thus sucrose is considered to bethe most cariogenic sugar, the arch criminal of dental caries.

Ans. 70.

• The text states that the early detection of incipient caries, limitation of caries activity before significant toothdestruction has occurred and the identification of high risk patients are the primary goals of an effective diagnosis and

treatment planning.

• Various diagnostic aids in the detection of caries at an early stage include:

1. Identification of subsurface demineralization (inspection, radiographic and dye uptake methods)

2. Bacterial testing

3. Assessment of environmental conditions such as pH, salivary flow etc.

• In the first method mentioned, the tooth surface can be examined, visually and tactilely.

• However the use of an explorer for caries detection is being replaced by visual and other diagnostic methods becauseinjudicious use of an explorer can result in actual cavitation in non-cavitated areas.

• Even though radiolucent areas in the proximal surface and below the occlusal enamel are interpreted as evidence of

caries, they do not indicate whether the surface has been cavitated.• The above discussion makes it quite clear that the visible light is one of the preferred methods for the diagnosis of

incipient caries.

Ans. 71.

- Chromium stainless steel crown was introduced by Humphrey.

- Factors to be considered in the pre-operative evaluation for a stainless steel crown:

1. Dental age of the patient: when a primary tooth can be expected to exfoliate within 2 years, amalgam restorations

may be performed.2. Co-operation of the patient: if a child is not able to co-operate because of age (< 3 years) then General Anesthesia

may be considered.

3. Patient motivation.4. Medically compromised or disabled children.

Now go through the indications of this crown:

• Primary or young permanent teeth with extensive carious lesions.

• Hypoplastic primary or permanent teeth that cannot be restored with amalgam or composite restorations.• Hereditary anomalies such as Amelogenesis or dentinogenesis imperfecta.

• Root canal treated teeth.

• An attachment where there is an indication of a crown and loop space maintainer.

• A restoration of a fractured tooth.

• Restoration of a first molar when it is to be used as an abutment for a distal extension appliance.Thus we can see that options 2, 3, 4 are clear indications of a stainless steel crown, thus providing us option A as an

answer of exclusion.

Ans. 72.Let us discuss the given situation:

• The child is 8 years old and as we know the lower premolars have an age range of 10 to 12 years for their eruption.

• Thus a minimum period of 2 years remains till the premolar will erupt.

• We also know that the greatest amount of space loss occurs within the first six months of loss of tooth, particularly by

the mesial migration of the first permanent lower molar, with the resultant block out of the premolar.• It is thus mandatory that the space be maintained till the premolar erupts, which is approximately the time when its

2/3rd root formation is completed. Thus the answer 1.

Ans. 73.• Constitutional delay in growth is a common cause of short stature in the mid-childhood.

• It is characteristically associated with normal average growth velocity and ultimate height attained is normal.

• Their skeletal maturation is slightly less than expected for their chronological age. Ratio between upper and lower

segments is normal or slightly immature.


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• The birth weight and height are normal but the rate of growth is less from early life.

• Pubertal growth spurt is delayed but extra years of pre-pubescent growth make up for the short stature of earlier years,so that the ultimate height is normal.

• The question provides all of these features and is thus a case of constitutional delay in growth.

Ans. 74.• A careful examination of the result of outbreeding in the human populations casts doubt on the hypothesis that

independently inherited tooth and jaw characteristics are a major cause of malocclusion.

• Before its discovery by the European explorers of the 18th century, Hawaii had a homogenous Polynesian population.• These people had larger stature, broad, well developed jaws and an unusual and distinctive form of the lower jaw

called as the Rocker’s jaw.

• Large scale migration of Europeans, Chinese and Japanese racial and ethnic groups into the islands, resulted in anexceptionally heterogenous modern population.

• Tooth size, jaw size and jaw proportion were all rather different for the Polynesian, Oriental and European

contributors to the Hawaian melting pot.

• Therefore if tooth and jaw characteristics were inherited independently, a high prevalence of severe malocclusion

would be expected in this population.

• It thus becomes clear that the incidence of malocclusion in a homogenous population is generally less than in a

hetreogenous population.

Ans. 75.• During the mixed dentition period the deciduous teeth are replaced by the permanent dentition.

• This period from 7 to 10 years can be divided into:1. First transitional period.

2. Inter-transitional period

3. Second transitional period

• In this period the chances of development of a malocclusion are more because any changes in the sequence of

eruption and shedding of the various teeth.

• Therefore the supervision of the child’s dentition is most critical in this period of mixed dentition particularly

between 7 to 10 years.

Ans. 76.• A normal feature of the deciduous dentition is the flush terminal plane, which means that the distal surfaces of the

upper and the lower deciduous second molars lie in the same vertical plane.• Thus the erupting first permanent molars will also be initially in a flush or end on relationship.

• For the transition of such an end on molar relation into a class I relation, the lower molar has to move forward by

about 3 to 5 mm relative to the upper molar.

• This occurs by the utilization of the physiologic spaces and the Leeway space in the lower arch and by the differential

forward growth of the mandible.

• The shift of the lower molar occurs as an early and a late mesial shift.

• Early mesial shift occurs by the utilization of the primate spaces where as the late shift occurs by the utilization of the

leeway space.

• Also remember that in Mesial step, the distal surface of the lower second primary molar is more mesial to that of the

upper. This may result in a class III malocclusion or may erupt directly in a normal class I molar relation.• Similarly, Distal step is the situation in which the distal surface of the lower second primary molar is more distal tothat of the upper. This may result in a class II malocclusion.

• The classification of the terminal plane relationships was given by Baume.

Ans. 77.• Hyalinization is a form of tissue degeneration characterized by the formation of a clear, eosinophilic, homogenous

substance.

• Hyalinization of the PDL denotes a compressed and locally degenerated area within the PDL.

• The changes observed during hyalinization are as follows:


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1. There is a gradual shrinkage of the PDL.

2. The cellular structures become indistinct, some nuclei become smaller-pyknotic and some of them disappear.3. The compressed collagen fibres gradually unite into a more or less cell free mass.

4. In addition, certain changes also occur in the ground substance.

5. There is a breakdown of the blood vessel walls leading to spilling of their contents.

6. osteoclasts are formed in the marrow spaces and adjacent areas of the inner bone surface after a period of 20 to30 hours.

• The presence of a hyaline zone in the PDL indicates that the ligament is non-functional and that bone resorption

cannot occur.

Ans. 78.

Malocclusions can be defined in three planes:

1. VERTICAL PLANE:

• This includes Deep bite and Open bite where in an abnormal vertical relation exists between the teeth of theupper and the lower arch.

• Deep bite demonstrates excessive vertical overlap between the upper and the lower incisors.

• Open bite represents the absence of vertical overlap between the upper and the lower teeth.2. TRANSVERSE PLANE:

• These inter arch malocclusions involve various kinds of cross bites.• Also refer to Proffit for conditions such as Scissor bite, X-occlusion and Buccal non-occlusion.

3. SAGGITAL PLANE: • Pre-normal Occlusion: the lower jaw being forwardly placed than the upper jaw.

• Post-normal occlusion: the lower jaw being more distally placed when the patient bites in centric occlusion.

Ans. 80.Acute necrotizing ulcerative gingivitis causes acute inflammation of gingiva and not chronic and is the answer of choice.

Clinical features 1) ANUG most often occurs as an acute disease. ANUG often undergoes a diminution in severity leading to a subacute

stage with milder clinical symptoms.

2) Characteristic lesions are punched out craterlike depression at crest of the interdental papillae, subsequently extending

to marginal and attached gingiva.

3) The gingival crater is covered with a gray, pseudomembranous slough, demarcated from the remainder of the gingivalmucosa by a pronounced linear erythema.

4) Spontaneous bleeding is seen.

5) Extremely sensitive touch and presents with constant radiating, gnawing pain with excessive amount of pasty saliva.

6) Necrosis of the tip of interdental papilla is present in 93%

Also remember:ANUG is also associated with decreased resistance to infection.

“Congen described that depression in host defense mechanism, particularly in PMN chemotaxis and phagocytosis in NUG

patients.”

Ans. 81.“Surgical technique may be necessary owing to the need for improved accessibility for root planning or regenerative surgery

of osseous defects. The papilla preservation flaps can be used with better postoperative results.”

As infrabony pocket involves regenerative treatment with bone grafts papilla preservation is first choice for this surgical

treatment.Remember:

Condition Preferred Flap

• For accessibility in anterior teeth segment Papillary Preservation Flap• For reconstructive osseous surgery

• For accessibility in non aesthetic zone Modified widman flap• For osseous defect closure by bone recontouring Apically displaced flap

• Decreased width of attached gingiva with thick pocket wall

• Long narrow gingival defect on single tooth Laterally displaced flap


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Ans. 82.1. The method for the prevention of epithelial migration along the cemental wall of the pocket that has gained wide

attention is the so-called guided tissue regeneration (GTR).

2. GTR consists of placing barriers of different types to cover the bone and periodontal ligament, thus temporary

separating them from the gingival epithelium.3. GTR not only prevents epithelial migration into the wound but also favours repopulation of the area by cells from the

periodontal ligament and bone.

Remember

Resorbable Membranes Non Resorbable Membrane

- Rat collagen - Polytetra fluoroethylene

- Bovine collagen - Teflon

- Cartilage membrane - Goretex

- Polylactic acid - Millipore filters- Vycril (polyglactin 10)

- Synthetic skin (Biobrane)

- Freeze-dried dura mater.

Ans.83.“Pus occurs in pockets with suppurative inflammation of the inner wall”.

Correlation of Clinical and Histopathologic Features of the periodontal Pocket

Clinical Features Histopathologic features

The gingival wall of the periodontal pocket

presents various degrees of bluish-red

discoloration; flaccidity; a smooth, shiny

surface, and pitting on pressure.

The discoloration is caused by circulatory flaccidity, by destruction of the

gingival fibers, surrounding tissues; the smooth, shiny surface results from

atrophy of the epithelium and edema; the pitting on pressure, by edema

and degeneration

Less frequently, the gingival wall may be pink

and firm.

In such cases, fibrotic changes predominate and degeneration, particularly

in relation to the inner surface of the pocket wall. However, despite this

appearance of health, the inner wall of the pocket probably presents some

degeneration and is often inflamed

Bleeding is elicited by gently probing the soft

tissue wall of the pocket.

Ease of bleeding results from increased vascular thinning and degeneration

of the epithelium in proximity of the engorged vessels to the inner wall ofthe pocket.

When explored with a probe, the inner aspectof the periodontal pocket is generally painful.

Pain on tactile stimulation is due to ulceration on inner aspect of the pocketwall.

In many cases, pus may be expressed by

applying digital pressure

Pus occurs in pockets with suppurative inflammation of the inner wall

Ans. 84.

- The epithelium of the lateral wall of the pocket presents striking proliferative and degenerative changes.

- The most severe degenerative changes in the periodontal pocket occur along the lateral wall.

- Progressive degeneration and necrosis of the epithelium lead to ulceration of lateral wall, exposure of the underlying

inflamed connective tissue and suppuration.

- The severity of the degenerative changes is not necessarily related to pocket depth. Ulceration of the lateral wall mayoccur in shallow pockets, and deep pockets are occasionally observed in which the lateral epithelium is relativelyintact or shows only slight degeneration.

Ans. 86.“We cannot measure incidence and can only estimate relative risk”- Case control study,

Advantages:

1. Relatively easy to carry out

2. Rapid and inexpensive compared to cohort studies

3. Requires comparatively fewer subjects


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4. Particularly suitable to investigate rare diseases

5. No risk to subjects.

Disadvantages:1. Problems of bias- relies on memory or past records

2. Selection of an appropriate control group may be difficult

3. We cannot measure incidence and can only estimate the relative risk.4. Does not distinguish between causes and associated factors.

Ans. 87.

• The estimation of chlorine needed to disinfect the filtered water is done by testing for chlorine demand.

• Chlorine demand is difference between the amount of chlorine added to a sample of water and the amount of chlorine

remaining at the end of a specified period.

• This is the amount of chlorine used up in destroying bacteria and in oxidising all of the organic substances in water.

• The point at which free Chlorine starts appearing in the water sample is called as breakpoint chlorination.• The method for finding out residual chlorine after the break point is achieved, is the Ortho Toluidine Arsente (OTA)

test.

Ans. 88.

“Standard error of proportion equals square root of pq/n”Where p = proportion of males

q = proportion of females

n = size of the sample

Ans. 89.

• Primary prevention as we know is the intervention before the occurrence of the disease.• All the options except A are treatment modalities after the disease has occurred.

• Only option A deals with measures taken to prevent the occurrence of the disease and is thus the answer of choice.

Refer to the table for the levels of prevention and their examples.

Ans.90.“The sample of organisms is obtained by the use of tongue blade (wooden spatulas) which is then pressed against

streptococcus mutans selective MSB (mitus salivarius bacitracin) agar in special petri dishes.”• Streptococcus mutans levels in saliva are measured as number of s.mutans colony forming units per unit volume of

saliva and culturing of the plaque samples from discrete sites such as occlusal fissures or proximal areas.

• Incubation is done on mitis salvarius agar (MSA) selective streptococcal medium with addition of high concentration

of sucrose 20% and 0.2 microns bacterium per ml (MSB) suppresses growth of most s.mutans colonies.

• The agar plates are incubated at 37C for 48 hrs in 95% at 5% CO2 gas mixture.• Interpretation: Streptococcus mutans> 105/mL of saliva is considered unacceptable.

• Colonisation of new surface does not occur readily unless the levels of S.mutans reaches 4.5X104 / ml for smooth

surface and 103 /ml for occlusal fissures.

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