Torque prescription for maxillary central incisor according to MBT in degrees is:

 # Torque prescription for maxillary central incisor according to MBT in degrees is:

A. 17

B. 10

C. -7

D. 0

The correct answer is A. 17.

Torque in orthodontics refers to the buccopalatal crown-root inclination of a tooth. To implement torque, larger dimensional archwires are inserted and engaged into brackets. This generates an activating force as the wire is manipulated into the bracket slot. Torque is not directly “in the wire.” Instead, it results from torsion in an archwire when it interacts with a bracket slot. When the wire twists compared to the bracket slot, it creates a couple (a rotational force) that affects the tooth’s inclination. Torque is not related to the angle of the bracket slot or the axial inclination of the tooth. In orthodontic treatment, torque control is often required, especially for maxillary incisors. Proper torque helps achieve an ideal inter-incisal angle, adequate incisor contact, and sagittal adjustment of the dentition for an ideal occlusion. The goal is to achieve the desired buccopalatal inclination of the crowns and roots. The MBT system is a popular pre-adjusted edgewise appliance system.

In the MBT system, torque prescription is based on the specific bracket design and the desired tooth movement. Orthodontists select brackets with predetermined torque values to achieve the desired crown-root inclination. The torque values are typically printed on the bracket prescription chart provided by the manufacturer. According to MBT, torque prescription for maxillary central incisor in degrees is 17 degrees. 

Which cusp on a maxillary first molar has two ridges: one that forms part of a transverse ridge and the other that forms part of an oblique ridge?

 # Which cusp on a maxillary first molar has two ridges: one that forms part of a transverse ridge and the other that forms part of an oblique ridge?

a. Mesiobuccal

b. Mesiolingual

c. Distobuccal

d. Distolingual

The correct answer is B. Mesiolingual. 

The mesiolingual cusp has triangular ridge as well as buccal ridge as shown in the figure of right maxillary first molar. 

From which view are only two roots visible on a maxillary first molar?

 # From which view are only two roots visible on a maxillary first molar?

a. Mesial

b. Distal

c. Buccal

d. Lingual

The correct answer is A. Mesial.

On both the maxillary first and second molars from the mesial view, two roots can be seen: the lingual

root and the mesiobuccal root, which is considerably wider buccolingually than the hidden distobuccal root.  On the first maxillary molar, the convex buccal outline of the mesiobuccal root often extends a little buccal to the crown outline, but the apex of this root is in line with the tip of the mesiobuccal cusp.

The furcations are likely to be farthest away from the cervical portion of the tooth in which of the following teeth?

 # The furcations are likely to be farthest away from the cervical portion of the tooth in which of the following teeth?

A. Mandibular first molar

B. Mandibular second molar

C. Mandibular third molar

D. Maxillary first molar

The correct answer is C. Mandibular third molar. 

Both maxillary and mandibular third molar roots are noticeably shorter than on firsts or seconds. They are very crooked, often curving distally, and more commonly fused most of their length resulting in a long root trunk with the furcation located only a short distance from the apices of the roots.