60-74 micrometer sized particles contained in:

 # 60-74 micrometer sized particles contained in: 

A. Coarse grit diamond bur 

B. Medium grit diamond bur 

C. Fine grit diamond bur 

D. Very fine grit diamond bur 

The correct answer is C. Fine grit diamond bur.

The particle sizes of coarse, medium, fine and very fine grit diamond burs are 125-150 micrometer, 88-125 micrometer, 60-74 micrometer and 38-44 micrometer respectively. 

The width of keratinized gingiva is measured as the distance from the:

 # The width of keratinized gingiva is measured as the distance from the: 

A. Free gingival margin to the mucogingival junction 

B. Cementoenamel junction to the mucogingival junction 

C. Free gingival groove to the mucogingival junction 

D. Free gingival margin to the base of the pocket 

The correct answer is A. Free gingival margin to the mucogingival junction.

Keratinized gingiva extends from the free gingival margin to the mucogingival junction. The attached gingiva extendsfrom the free gingival groove to the mucogingival junction. 

What is a second-order bend in orthodontic wire?

# What is a second-order bend in orthodontic wire? 

A. Bend to position a tooth buccolingually 

B. Bend to provide angulation of a tooth in mesiodistal direction (tip) 

C. Bend to provide correct angulation of a tooth in labiolingual direction (torque) 

D. Bend to rotate a tooth 

The correct answer is B. Bend to provide angulation of a tooth in mesiodistal direction (tip) 

A second-order bend is placed to provide angula tion of a tooth in the mesiodistal direction, also called “tip.” A first-order bend is placed in an arch wire to position a tooth in the labiolingual direc tion (in-out bend) or to rotate a tooth as seen in the occlusal plane. A bend to provide angulation in the labiolingual direction is called a third-order bend (torquing bend). 

The membrane that separates the enamel organ and the dental papilla just prior to dentin formation is called:

 # The membrane that separates the enamel organ and the dental papilla just prior to dentin formation is called:

A. Inner enamel epithelium

B. Outer enamel epithelium

C. Membrana preformativa

D. Cell-free zone

The correct answer is C. Membrana preformativa.

The dental papilla is enclosed in the invaginated portion of the enamel organ. Before the inner enamel epithelium begins to produce enamel, the peripheral cells of the mesenchymal dental papilla differentiate into odontoblasts under the organizing influence of the epithelium. First, they assume a cuboidal form; later they assume a columnar form and acquire the specific potential to produce dentin. The dental papilla ultimately gives rise to dental pulp, once the dentin formation begins at the cuspal tip of the bell stage tooth germ. The basement membrane that separates the enamel organ and the dental papilla just prior to dentin formation is called the membrana preformativa.