The best space maintainer for the early loss of upper primary incisor is the pin and tube maintainer, because :

 # The best space maintainer for the early loss of upper primary incisor is the pin and tube maintainer, because :

A. It is aesthetically acceptable 

B. It does not injure the upper lip 

C. It is easy to fabricate 

D. It allows lateral growth of the bone

The correct answer is D. It allows lateral growth of the bone.

The removable pin and tube space maintainer is designed to prevent space loss after the premature loss of a primary incisor. It allows for the natural lateral growth of the bone and provides sufficient space for the permanent tooth to erupt properly. This type of space maintainer is usually considered effective and well-tolerated by patients. While aesthetics and ease of fabrication are also important considerations, the primary purpose of a space maintainer is to preserve the space for the permanent tooth and support proper oral development.

Salt and pepper appearance in MRI of salivary gland is suggestive of:

 # Salt and pepper appearance in MRI of salivary gland is suggestive of:

A. Sjogren syndrome

B. Thalassemia

C. Mumps

D. Salivary gland tumor

The correct answer is A. Sjogren syndrome.

A salt and pepper appearance of the salivary glands on MRI is particularly suggestive of Sjogren syndrome. Salt and pepper appearance of IOPA X rays is seen in Thalassemia.

Which visceral arch is rudimentary in humans?

 # Which visceral arch is rudimentary in humans?

A. 4th 

B. 5th 

C. 6th

D. 7th

The correct answer is B. 5th.

The pharyngeal arches, also known as visceral arches, are structures seen in the embryonic development of vertebrates that are recognisable precursors for many structures.

In the human embryo, the arches are first seen during the fourth week of development. They appear as a series of outpouchings of mesoderm on both sides of the developing pharynx. The vasculature of the pharyngeal arches is known as the aortic arches.

During human, and all vertebrate development, a series of pharyngeal arch pairs form in the developing embryo. These project forward from the back of the embryo toward the front of the face and neck. Each arch develops its own artery, nerve that controls a distinct muscle group, and skeletal tissue. The arches are numbered from 1 to 6, with 1 being the arch closest to the head of the embryo, and arch 5 existing only transiently.

What is the most superior point of the external auditory canal?

 # What is the most superior point of the external auditory canal?

A. Sella

B. Porion

C. Basion

D. Orbitale

The correct answer is B. Porion.

The porion is the most superior point of the external auditory canal. The sella is the center of the hypophyseal fossa. The basion is the most anterior point of the foramen magnum. The orbitale is the most inferior point of the infraorbital rim.