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. 

What is the main purpose of miniplates in orthodontic practice?

 # What is the main purpose of miniplates in orthodontic practice?

A. To manage skeletal discrepancy without dental adverse effects 

B. To serve as an alternative anchorage system for mini-implants 

C. To withstand torsional force 

D. To anchor soft tissue to root apices

The correct answer is: A. To manage skeletal discrepancy without dental adverse effects. 

Miniplates are an alternative form of orthodontic TADs. They are anchored on skeletal bone using monocortical titanium screws and are indicated for orthopaedic traction to manage skeletal discrepancy without dental adverse effects. They can also be used as an alternative anchorage system when mini-implant insertion is unsatisfactory. While miniplates can be used as an alternative anchorage system, their primary purpose is not specifically to serve as an alternative to mini-implants.

Unlike mini-implants, miniplates can resist various types of force applications and have a lower failure rate. They are able to withstand force with a magnitude of 400–500 g. Additionally, the portion of a miniplate covered by soft tissue can be anchored apically to root apices, helping to avoid potential root damage and reduce soft tissue irritation.