Snyder's test tell us the:

 # Snyder's test tell us the: (AIPG-96)

a) Exact nature of microorganisms

b) Combined acidogenic nature of microorganisms

c) Enamel dissolving capacity of saliva

d) All of the above

The correct answer is B. Combined acidogenic nature of microorganisms

Snyder test measures the ability of the salivary microorganisms to form organic acids from a carbohydrate medium. In this test the glucose agar medium contains an indicator dye "Bromocresol green" which changes color from green to yellow in the range of PH 5.4 to 3.8

 

Colour observations in snyder test:- 

24 hrs	48 hrs	72 hrs
If yellow marked caries susceptibility	If yellow  definate caries susceptibility	If yellow  limited caries susceptibility
If green continue to incubate and observe at 48 hrs	If green continue to incubate and observe at 72 hrs	If green caries inactive

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Caries activity in very young children is evaluated by:

 # The valuable test for evaluating caries activity in very young children: (KCET-10)

a) Lactobacillus colony count test

b) Swab test

c) Alban test

d) Colorimetric Snyder test

The correct answer is B. Swab Test.

Swab test was developed by Grainger et al. It has an advantage over the other tests in that no collection of saliva is necessary. So it is valuable in evaluating caries activity in very young children.

 Procedure:

The oral flora is sampled by swabbing the buccal surfacesof the teeth with a cotton applicator, and the sample is subsequently incubated in the medium. The change in pH following a 48-hour incubation period is either read on a pH meter or read by the use of a color indicator.

 Principle:

Same as Snyder test

INTERPRETATION
pH	Caries activity
<= 4.1	Marked caries activity
4.2 to 4.4	Active
4.5 to 4.6	Slightly active
> 4.6	Caries inactive

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The visual sense has maximum acuity at:

 # The visual sense has maximum acuity at :

A. Ora serrata

B. Optic disc

C. Macula lutea

D. Fovea centralis

The correct answer is D. Fovea Centralis.

At the posterior pole of the eye, 3 mm lateral to the optic disc there is another depression of similar size called the macula lutea. It is avascular and yellow in color. The center of the macula is further depressed to form the fovea centralis. This is the thinnest part of the retina. It contains cones only and it is the site of maximum visual acuity. 

The rods and cones are the light receptors of the eye. The rods contain a pigment called visual purple. They can respond to dim light (Scotopic vision). The periphery of the retina contains only rods, but the fovea centralis contains no rods. The cones can only respond to bright light (photopic vision) and are sensitive to color. The fovea centralis has only cones. 

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The aqueous humor is secreted from:

 # The aqueous humor is secreted from:

A. Scleral spur

B. Sinus venosus sclerae

C. Ciliary processes

D. Suprachoroid lamina

The correct answer is C. Ciliary processes.

Aqueous humor is a clear fluid which fills the space between the cornea in front and the lens behind in the anterior segment. This space is divided by the iris into anterior and posterior chambers which communicates freely with each other via pupil. The aqueous humor is secreted into the posterior chamber from the capillaries in the ciliary processes. It passes into the anterior chamber through the pupil. From the anterior chamber it is drained into the anterior ciliary veins through the iridocorneal angle or angle of anterior chamber located between the fibres of the ligamentum pectinatum and the canal of Schlemm. Interference with the drainage of the aqueous humor into the canal of Schlemm results in an increase of intraocular pressure (glaucoma). This produces cupping of the optic disc and pressure atrophy o the retina causing blindness. 

The vitreous humor is clear gel that fills the space between the lens and the retina of the eyeball of humans. It is often referred to as the vitreous body or simply 'the vitreous'. It is produced by certain retinal cells. 

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The cornea is nourished by:

 # The cornea is nourished by:

A. Aqueous humor

B. Lymphatic fluid

C. Lacrimal fluid

D. All of the above

The correct answer is B. Lymphatic fluid.

The cornea is more convex than the sclera, but the curvature diminishes with age. It is separated from the iris by a space called the anterior chamber of the eye. The cornea is avascular and is nourished by lymph which circulates in the numerous corneal spaces. Pain is the only sensation aroused from the cornea. 

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Medial squint may be the result of a lesion involving:

 # Medial squint may be the result of a lesion involving:

A. III cranial nerve

B. IV cranial nerve

C. VI cranial nerve

D. Optic nerve

The correct answer is. C. VI cranial nerve.

Medial squint is the result of palsy of lateral rectus of eye. All the extraocular muscles are supplied by the third cranial nerve (Oculomotor nerve) EXCEPT Lateral rectus which is supplied by sixth cranial nerve (Abducent nerve) and Superior Obique which is supplied by fourth cranial nerve (Trochlear nerve). 

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Superior rectus helps in:

 # Superior rectus helps in all of the following movements EXCEPT:

A. Upward rotation

B. Lateral rotation

C. Intorsion

D. Medial rotation

The correct answer is B. Lateral rotation. 

All the rectus muscles are involved in medial rotation of eye except the lateral rectus. Lateral rectus is the only rectus muscle involved in lateral rotation. 

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