The root amputation procedure involving the removal of one half of the crown and one root

# The root amputation procedure involving the removal of one half of the crown and one root in a mandibular molar is called as:

A. Bi-cuspidization

B. Hemisection

C. Root resection

D. Apicoectomy 

The correct answer is B. Hemisection.

RADISECTOMY AND HEMISECTION

Definition: Radisectomy denotes the removal of one or more roots of a molar.

Hemisection refers to sectioning of the crown of a molar tooth, with either the removal of half the crown and its supporting root structure or the retention of both halves, to be used after reshaping and splinting as two premolars.

Reference: GROSSMAN’S ENDODONTIC PRACTICE 14TH EDITION, Page NO: 447

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Best technique of wedging for a patient with the gingival recession

 # For a patient with the gingival recession, The best technique of wedging is:

A. Piggy back

B. Double wedging

C. Wedge wedging

D. Single wedge

The correct answer is A. Piggy Back.

Piggy-back wedging technique

If the wedge is significantly apical of the gingival margin, a second (usually smaller) wedge may be placed on top of the first to wedge adequately the matrix against the margin. This type of wedging is particularly useful for patients whose interproximal tissue level has receded.

Reference: Sturdevant’s Art and Science of Operative Dentistry Second South Asia Edition 2019, Page No: 362

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Agent used as a die hardener

# Which of the following agents is used as a die hardener?

A. Cyanoacrylate

B. Nail polish

C. Volatile relief agents

D. Composite resin

The correct answer is A. Cyanoacrylate.

Gypsum dies are sometimes modified to (1) make them more abrasion-resistant, (2) change the dimensions of the dies, (3) increase the refractoriness of the dies, or (4) produce a combination

of these effects. Several means are used to increase the abrasion resistance, including silver plating, coating the surface with cyanoacrylate adhesive, and adding a die hardener to the gypsum.

Reference: PHILLIPS’ SCIENCE OF DENTAL MATERIALS, Anusavice, Shen, Rawls, 12th Edition, Page No: 211

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Factors associated with external root resorption

 # Following are the factors associated with external root resorption except:

A. Grafting of alveolar clefts

B. Cysts

C. Orthodontic therapy

D. Endodontic therapy

The correct answer is A. Graft of alveolar clefts.

Risk factors associated with severe resorption are:

- Shorter than average roots.

- Previously traumatized teeth.

- Nonvital teeth.

- Teeth subjected to excessive forces.

- Combination of orthodontic and orthognathic procedures.

Reference: Shafer’s Textbook of ORAL PATHOLOGY, 7th Edition, Page No: 930

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Test for measuring hardness

 # Which of the following is a test for measuring hardness?

A. Knoop

B. Toughness

C. Yield strength

D. Resilience

The correct answer is A. Knoop.

The tests most frequently used in determining the hardness of dental materials are known by the names

Barcol, Brinell, Rockwell, Shore, Vickers, and Knoop. Selection of the test should be determined on the basis of the material being measured.

The Knoop hardness test employs a diamond-tipped tool. The impression is rhombic in outline, and the length of the largest diagonal is measured. The load is divided by the projected area to give the Knoop hardness number (usually abbreviated as HK or KHN).

Reference: PHILLIPS’ SCIENCE OF DENTAL MATERIALS, Anusavice, Shen, Rawls, 12th Edition, Page No: 64

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Mechanism of adhesion of glass ionomer cement restoration with tooth surface:

 # The mechanism of adhesion of glass ionomer cement restoration with tooth surface is by means of:

A. Carboxyl group of polymer chains

B. Chelates with metal ion

C. C=C double bond

D. Hydroxyl group

The correct answer is A. Carboxyl group of polymer chains.

Glass ionomers bond to tooth structure by chelation of the carboxyl groups of the polyacrylic acids with the calcium in the apatite of the enamel and dentin, in a manner similar to polycarboxylate cement.

Reference: PHILLIPS’ SCIENCE OF DENTAL MATERIALS, Anusavice, Shen, Rawls, 12th Edition, Page No: 321

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During the setting of alginate impression materials:

 # During the setting of alginate impression materials:

A. Trisodium phosphate reacts preferentially with calcium sulfate

B. Trisodium phosphate reacts preferentially with sodium alginate

C. The colloidal gel state changes to a sol

D. The material in contact with the soft tissues set last

The correct answer is. A. Trisodium phosphate reacts preferentially with calcium sulfate

A water-soluble phosphate salt (e.g., trisodium phosphate) is added to the composition as a retarder to extend the working time. The strategy is that the calcium ions will react preferentially with the phosphate ions in the solution. Thus, the rapid reaction between calcium ions and the soluble alginate is

deferred until phosphate ions from trisodium phosphate are exhausted. The amount of retarder is adjusted to provide the proper setting time. A similar gelation process is expected with the modified alginate product.

Reference: PHILLIPS’ SCIENCE OF DENTAL MATERIALS, Anusavice, Shen, Rawls, 12th Edition, Page No: 172

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