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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