Which of the following elements are the constituents of white gold alloys?

 # Which of the following elements are the constituents of white gold alloys?

A. Gold and copper

B. Silver and palladium

B. Palladium and platinum

D. Copper and Palladium

The correct answer is B. Silver and palladium.

White gold is an alloy of gold and at least one white metal (usually nickel, silver, or palladium). Like yellow gold, the purity of white gold is given in karats.

White gold's properties vary depending on the metals used and their proportions. As a result, white gold alloys can be used for many different purposes: while a nickel alloy is hard and strong, and therefore good for rings and pins; gold–palladium alloys are soft, pliable, and good for white-gold gemstone settings, sometimes with other metals, like copper, silver, and platinum, added for weight and durability (although this often requires specialized goldsmiths). The term white gold is used very loosely in the industry to describe karat gold alloys with a whitish hue. The word white covers a broad range of colors that borders or overlaps pale yellow, tinted brown, and even very pale rose. The jewelry industry often conceals these off-white colors by rhodium plating; thus it is a common misconception that the color of the rhodium plating, which is seen on many commercial pieces, is the actual color of white gold.

Which of the following is the gene for sex determination?

 # Which of the following is the gene for sex determination?

A. HOX

B. Shh

C. SRY

D. Rb gene

The correct answer is C. SRY.

Some species (including humans) have a gene SRY on the Y chromosome that determines maleness. Members of SRY-reliant species can have uncommon XY chromosomal combinations such as XXY and still live. Human sex is determined by the presence or absence of a Y chromosome with a functional SRY gene. Once the SRY gene is activated, cells create testosterone and anti-müllerian hormone which typically ensures the development of a single, male reproductive system. In typical XX embryos, cells secrete estrogen, which drives the body toward the female pathway.

Torque in orthodontics refers to:

 # Torque in orthodontics refers to:

a. The change in mesiodistal inclination of teeth

b. The change in labiolingual inclination of teeth

c. The rotation of teeth

d. None of the above

The correct answer is B. The change in labiolingual inclination of teeth.

Torquing is considered as reverse tipping during which there is movement of root only without the movement of the crown. This type of tooth movement is usually used to correct the effects of uncontrolled tipping. 

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Which of the following materials used in orthodontics commonly causes sensitivity?

 # Which of the following materials used in orthodontics commonly causes sensitivity?

A. Steel

B. Ceramic

C. Nickel

D. Plastic

The correct answer is C. Nickel.

Most allergies in orthodontics are related to latex and nickel. Nickel can evoke IgE-mediated (immediate) and cell-mediated (delayed) hypersensitivity reactions. 

Double cantilever spring OR Z-spring

 Z-Spring

Double cantilever/Z-spring can be used for the labial movement of palatally locked incisors and also for correcting minor rotations of these teeth.

Parts of Z-Spring

a. Square loop

b. Two helices

c. Retentive arm

d. Retentive tag

Helices of Z-spring

There are two helices of small internal diameter.

Squarsh loop: Active arm with squarsh loop is incorporated at the free end of active arm and it helps in preventing soft tissue damage.

Retentive arm: It has a long retentive arm of about 10 to 12 mm length, which gets embedded in acrylic base material.

Retentive tag: Retentive tag of Z-spring is perpendicular to the retentive arm and is of 2 to 3 mm in length.

Fabrication

 Stainless steel wire of 0.5 mm or 23 gauge isn used for the fabrication of Z-spring.

 Pliers used: Universal pliers can be used for the fabrication of Z-spring.

 Z-spring can be designed to more one or two incisor in a labial direction over equal distances.

 The spring is constructed such that it is perpendicular to the palatal surface of the teeth to be moved.

 Z-spring is a supported spring and needs boxing in the wax prior to acrylization. However, the helices are kept free from acrylic so that they can be activated.

Activation of Z-Spring

 For labial movement of incisors, the Z-spring is activated by simultaneously opening both helices by 2 to 3 mm.

 For correction of minor rotations, activation is done by opening only upper helix by 2 to 3 mm.

Uses

Z-spring is used for:

a. Labial movement of one or two incisors. It is often used for correction of anterior crossbite occurring due to palatally locked upper incisors.

b. It can also be used for the correction of mild rotation of incisors.

MCQs in Endodontics - Biomechanical Preparation

# The root canal instrument most likely to break during use is a:
A. File
B. Broach
C. Reamers
D. Spreaders

# While root canal biomechanical preparation apical constriction is enlarged to 50 sized instrument. You would like to:
A. Use reverse filling technique
B. Reinstrument with larger instrument 1 mm short of previous preparation
C. Fit a 50 mm cone and condense carefully
D. Fill with 40 sized cone