Dentosphere : World of Dentistry

Tarnish generally occurs in the oral cavity due to:

# Tarnish generally occurs in the oral cavity due to:

A. Formation of hard and soft deposits

B. Pigment producing bacteria

C. Formation of their oxides, sulphides or chlorides

D. All of the above

The correct answer is D. All of the above.

Tarnish: It is the surface discoloration or alteration of the surface finish or luster. It generally occurs due to formation calculus, plaque on the surface of the metal. It also occurs due to formation of oxides, sulfides or chlorides. Tarnish is the forerunner of corrosion.

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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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