Which of the following alloys exhibit superelasticity and shape memory

 # Which of the following alloys exhibit superelasticity and shape memory?

A. Nitinol

B. Beta titanium

C. Optiflex

D. Stainless steel

The correct answer is A. Nitinol.

The nickel-titanium alloys used in dentistry are based upon the equiatomic intermetallic compound NiTi, which contains 55% nickel and 45% titanium by weight. Orthodontic wire alloys contain small amounts of other elements, such as cobalt, copper, and chromium.

The alloy name “Nitinol” originally came from the two elements nickel (Ni) and titanium (Ti) and the Naval Ordnance Laboratory (NOL) where these alloys were developed. Superelasticity and shape memory are the properties exhibited by Nitinol.

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Which die material has a hazardous (lethal) potential during fabrication?

 # Which die material has a hazardous (lethal) potential during fabrication?

A. Improved stone

B. Silver amalgam

C. Electrodeposited silver

D. Epoxy resin

The correct answer is C. Electrodeposited silver.

• Has a lethal potential due to the Electro usage of silver cyanide plated silver 

• Polysulphide impressions can be easily electro plated

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The coefficient of thermal expansion of which of the following dental materials is the highest?

 # The coefficient of thermal expansion of which of the following dental materials is the highest?

A. Amalgam

B. Gold inlay

C. Silicate cement

D. Acrylic resins

The correct answer is D. Acrylic resins.

Linear coefficient of thermal expansion (α = coefficient of linear expansion (°C−1))

Tooth 9 - 11

Silicate 8

Unfilled acrylate 81

Composites 28 - 45

Amalgam 25

Direct gold 18

Aluminous porcelain 6 - 7

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The glass ionomer cement is not recommended for:

 # The glass ionomer cement is not recommended for:

A. Class V restoration

B. Class III restoration

C. Class IV restoration

D. None of the above

The correct answer is C. Class IV restoration 

INDICATIONS OF GIC

- The restoration of caries lesions on the roots of patients with active caries is the primary indication for the use of a glass ionomer as a restorative material.

- Because of their limited strength and wear resistance, glass ionomers are indicated generally for the restoration of low-stress areas (not for typical Class I, II or IV restorations), where caries activity potential is of significant concern.

- In addition to being indicated for root-surface caries lesions in Class V locations, slot-like preparations in Class II or III cervical locations (not involving the proximal contact) may be restored with glass ionomers, if access permits.

- Cervical defects of idiopathic erosion or abrasion origin (or any combination) also may be indications for restoration with glass ionomers, if esthetic demands are not critical.

 Reference: Sturdevant’s Art and Science of Operative Dentistry Second South Asia Edition 2019, Page No: 540

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Antibiotic prophylaxis is not recommended in:

 # Antibiotic prophylaxis is not recommended in:

a) Making of impressions 

b) Dental extraction

c) Replantation of tooth 

d) Gingivectomy

The correct answer is A. Making of impressions.

All dental procedures that involve manipulation of gingival tissue or the periapical region of teeth or perforation of the oral mucosa need antibiotic prophylaxis to prevent Bacterial endocarditis. Procedures such as anesthetic injections through non infected areas, taking dental radiographs, placement of removable prosthodontic/orthodontic appliances, adjustment of ortho appliances, placement of brackets, shedding of deciduous teeth, bleeding from trauma to lips or oral mucosa do not need antibiotic prophylaxis.

Cardiac conditions requiring prophylaxis include prosthetic cardiac valve, previous infective endocarditis, congenital heart disease, cardiac transplantation recipients who develop cardiac valvulopathy. They may be given oral Amoxicillin 2 gm/ Azithromycin SOOmg/ Cephalexin 2gm/ Clindamycin 600mg (OR) Ampicillin 2 gm IM or IV/ Cefazolin or Ceftriaxone 1 gm IM or IV/ Clindamycin phosphate 600mg IM or IV.

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# Serial extraction is contraindicated in:

 # Serial extraction is contraindicated in:

A. Open bite

B. Deep bite

C. Class II and III malocclusion with skeletal abnormalities

D. All of the above

The correct answer is D. All of the above.

Contraindications to Serial Extraction are:

1. Mild to moderate crowding—tooth size arch length deficiency < 5 mm per quadrant.

2. Class II division 2 and Class III malocclusions.

3. Spaced dentition.

4. Congenital absence—anodontia/oligodontia.

5. Extensive caries involving permanent first molars, which cannot be conserved.

6. Open bite and deep bite, which should be corrected first.

Reference: Textbook of Orthodontics, 2nd Edition, Gurkeerat Singh, Page No: 569

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Pericision is carried out as an adjunct retention for:

 # Pericision is carried out as an adjunct retention for:

A. Midline diastema

B. Rotation

C. Proclination

D. Extrusion

The correct answer is B. Rotation.

It is generally assumed that a stable position of the teeth in the dental arch after orthodontic tooth

movement can only be established when the connective tissues of the gingiva have been allowed to adapt to the newly created situation. Supracrestal gingival fibers of an orthodontically moved tooth get

stretched and undergo readaptation very slowly. The pull of these fibers is a major factor in relapse. If these supracrestal fibers are sectioned and allowed to heal while the teeth are held in the proper position, relapse caused by gingival elastic fibers is greatly reduced.

Reattachment of these fibers at a new relaxed position on the root surface stabilizes the tooth in its new

position. This procedure is effective in controlling relapse of derotated teeth.

Reference: Textbook of Orthodontics, 2nd Edition Gurkeerat Singh, Page 279

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