Cause of osteogenesis imperfecta is:

# Cause of osteogenesis imperfecta is:

A. Defect in type I collagen

B. Defect in type II collagen

C. Defect in maturation process

D. Defect in calcification process

The correct answer is A. Defect in type I collagen.

Osteogenesis imperfecta (OI) is a serious disease, the molecular pathogenesis of which is being elucidated and it bears a superficial relatedness to dentinogenesis imperfecta, a milder condition affecting mesodermal tissues. It is a condition resulting from abnormality in the type I collagen, which most commonly manifests as fragility of bones. Although osteogenesis imperfecta is generally recognized as representing a hereditary autosomal dominant characteristic, autosomal recessive and nonhereditary types also occur.

Reference: Shafer’s Textbook of ORAL PATHOLOGY, 7th Edition, Page No: 699

CLICK HERE FOR MORE MCQs

Dysplastic changes, carcinoma in situ or even early invasive cancer is seen in:

# Which of the following clinical lesions is most likely to harbor dysplastic changes, carcinoma in situ or even early invasive cancer?

A. Erythroplakia

B. Lichen planus

C. Leukoplakia

D. Stomatitis nicotiana

The correct answer is A. Erythroplakia.

Erythroplakia

(Erythroplasia of Queyrat)

Whilst leukoplakia is a relatively common condition, erythroplakia is rare. In contrast to leukoplakia, erythroplakia is almost always associated with premalignant changes histologically and is, therefore, the most important precancerous lesion.

The high rate of premalignant and malignant changes noticed in erythroplakia is true for all clinical varieties of this lesion and not solely a feature of speckled erythroplakia. Different studies have demonstrated that 80–90% of erythroplakias are histopathologically either severe epithelial dysplasia, carcinoma in situ, or invasive carcinoma.  

 Reference: Shafer’s Textbook of ORAL PATHOLOGY, 7th Edition, Page No: 95

CLICK HERE FOR MORE MCQs

Most sensitive to radiation induced cancer?

 # Which of the following is the most sensitive to radiation induced cancer?

A. Nerves

B. Female breast

C. Thyroid

D. Skin

The correct answer is B. Female breast.

Susceptibility of Different Organs to Radiation-Induced Cancer

High: Colon, Stomach, Lung, Bone marrow (leukemia), female breast

Intermediate: Bladder, Liver, Thyroid

Low: Bone surface, Brain, Salivary glands, skin

Reference: Oral Radiology Principles and Interpretation, 7th Edition, Page no 26

CLICK HERE FOR MORE MCQs

 

Tetanus is due to:

# Tetanus is due to:

A. Exotoxin fixed to motor end plate

B. Endotoxin fixed to motor end plate

C. Circulating exotoxin

D. Circulating endotoxin

The correct answer is A. Exotoxin fixed to motor end plate.

Clostridium tetani produces two types of toxins:

 1. Endotoxin-cardiotoxin- selective on hemopoetic cells and cardiac tissue 

2. exotoxin; Tetanospasmin acts on CNS.it acts at four sites

i). Motor end plate 

ii). Brain 

iii). spinal chord and 

iv) sympathetic nervous system. 

This Tetanospasmin inhibits cholinesterase at the motor end plate and as a result there is pooling of Acetyl choline resulting in sustained state of clonic muscle spasm, exotoxin travels to the CNS and it causes hyperexcitibity of the motor neurons at the Anterior horn cells there by evoking explosive spasms to sensory stimuli, once exotoxin is fixed in CNS, it cannot be neutralised by the antitoxin. 

C. tetani is an anaerobic， gram-positive， spore-forming rod whose spores are highly resilient and can survive readily in the environment throughout the world. Spores resist boiling and many disinfectants. In addition， C. tetani spores and bacilli survive in the intestinal systems of many animals， and fecal carriage is common. The spores or bacteria enter the body through abrasions， wounds， or (in the case of neonates) the umbilical stump. Once in a suitable anaerobic environment， the organisms grow， multiply， and release tetanus toxin， an exotoxin that enters the nervous system and causes disease. Very low concentrations of this highly potent toxin can result in tetanus (minimum lethal human dose， 2.5 ng/kg).

Genome sequencing of C. tetani has allowed identification of several exotoxins and virulence factors. Only those bacteria producing tetanus toxin ( tetanospasmin) can cause tetanus. Although closely related to the botulinum toxins in structure and mode of action， tetanus toxin undergoes retrograde transport into the central nervous system and thus produces clinical effects different from those caused by the botulinum toxins,  which remain at the neuromuscular junction.

Reference: S. Das Manual of Surgery and Harrison's Principles of Internal Medicine, 19th Edition, Page no: 984

CLICK HERE FOR MORE MCQs

The potency of the midazolam is:

 # The potency of the midazolam is:

A. Thrice that of diazepam

B. Twice that of diazepam

C. 10 times that of diazepam

D. 5 times that of diazepam

The correct answer is A. Thrice that of diazepam.

Midazolam This BZD is water soluble, nonirritating to veins, faster and shorter acting (t½ 2 hours) and 3 times more potent than diazepam. Fall in BP is somewhat greater than with diazepam. It is being preferred over diazepam for anaesthetic use: 1–2.5 mg i.v. followed by 1/4th supplemental doses. Also used for sedation of intubated and mechanically ventilated patients and in other critical care anaesthesia as 0.02–0.1 mg/kg/hr continuous i.v. infusion.

Reference: Essentials of Medical Pharmacology, Seventh Edition, KD Tripathi, Page 383

CLICK HERE FOR MORE MCQs

Saliva plays a vital role in the:

 # Saliva plays a vital role in  the ________ of a complete denture.

A. Retention

B. Stability

C. Support

D. Esthetics

The correct answer is A. Retention.

Sufficient amount of saliva is necessary for the maintenance of oral health and comfort. In this respect,

saliva is particularly important in wearers of removable dentures to protect the oral mucosa from mechanical irritation and infections and to achieve retention in complete dentures. The normal unstimulated salivary flow rate is 0.38±0.21 ml/min. Impaired salivary secretion or xerostomia is likely, if the unstimulated flow rate is less than 0.12 ml/min. Of the whole unstimulated saliva, 40 percent is derived from the submandibular glands and 8 percent from mucosal glands. The normal stimulated salivary flow rate is less than 0.60 ml/min of the whole stimulated saliva and 50 to 65 percent is

derived from the parotid glands.

Reference: Textbook of Complete Denture PROSTHODONTICS, Page NO. 3

CLICK HERE FOR MORE MCQs

Rheumatoid arthritis in children is known as:

 # Rheumatoid arthritis in children is known as:

A. Still’s disease

B. Kamura’s disease

C. Hansen’s disease

D. Degenerative joint disease

The correct answer is A. Still's disease.

Inflammatory arthritis occurs rarely in children. Several distinct subtypes are recognised. Systemic

juvenile idiopathic arthritis (JIA; formerly known as Still’s disease) is a systemic disorder characterised by fever, rash, arthritis, hepatosplenomegaly and serositis in association with a raised ESR and CRP. Autoantibody tests are negative.

Reference: Davidson’s Principles and Practice of Medicine, 22nd Edition 2014, Page no: 1104

CLICK HERE FOR MORE MCQs