According to Edward H. Angle's classification of malocclusion, what is the defining characteristic of Class III malocclusion?

 # According to Edward H. Angle's classification of malocclusion, what is the defining characteristic of Class III malocclusion?

A) Normal relationship of the molars but malposed teeth

B) Lower molar distally positioned relative to the upper molar

C) Lower molar mesially positioned relative to the upper molar

D) Correct line of occlusion with rotated teeth

The correct answer is C. Lower molar mesially positioned relative to the upper molar.

Angle’s classification of malocclusion in the 1890s was an important step in the development of orthodontics because it not only subdivided major types of malocclusion but also included the first clear and simple definition of normal occlusion in the natural dentition. Angle’s postulate was that the upper first molars were the key to occlusion and that the upper and lower molars should be related so that the mesiobuccal cusp of the upper molar occludes in the buccal groove of the lower molar. If the teeth were arranged on a smoothly curving line of occlusion and this molar relationship existed, then normal occlusion would result. This statement, which 100 years of experience has proved to be correct except when there are aberrations in the size of teeth, brilliantly simplified normal occlusion.

Angle then described three classes of malocclusion, based on the occlusal relationships of the first molars:

• Class I: Normal relationship of the molars, but line of occlusion incorrect because of malposed teeth, rotations, or other causes

• Class II: Lower molar distally positioned relative to upper molar, line of occlusion not specified

• Class III: Lower molar mesially positioned relative to upper molar, line of occlusion not specified

Ref: Proffit, W. R., Fields, H., Msd, D. M., Larson, B., & Sarver, D. M. (2019). Contemporary Orthodontics, 6e: South Asia Edition-E-Book. Elsevier India.

What was Norman Kingsley's contribution to orthodontics during the latter half of the 19th century?

 # What was Norman Kingsley's contribution to orthodontics during the latter half of the 19th century?

A) He developed the first orthodontic appliances in Greek materials.

B) He was among the first to use extraoral force to correct protruding teeth.

C) He introduced the concept of occlusion in the natural dentition.

D) He focused on the removal of teeth for various dental problems.

The correct answer is B. He was among the first to use extraoral force to correct protruding teeth.

After 1850 the first texts that systematically described orthodontics appeared, the most notable being Norman Kingsley’s Oral Deformities. Kingsley, who had a tremendous influence on American dentistry in the latter half of the 19th century, was among the first to use extraoral force to correct protruding teeth. He was also a pioneer in the treatment of cleft palate and related problems.

Ref: Proffit, W. R., Fields, H., Msd, D. M., Larson, B., & Sarver, D. M. (2019). Contemporary Orthodontics, 6e: South Asia Edition-E-Book. Elsevier India.

Initial clicking of TMJ is a sign of:

 # Initial clicking of TMJ is a sign of:

A. Retruded condyle

B. Unevenness of condylar surfaces

C. Incoordination between condylar surfaces and disc

D. Condyle too far anterior in relation to disc

The correct answer is A. Retruded condyle.

Early stages of disc displacement are characterised by clicking. Clicking can be heard while opening the mouth, while closing the mouth, or both. An opening click signifies recapture of the displaced disc between the articulating joint surfaces. A closing click occurs just prior to tooth contact and is not as loud as the opening click. When the disc becomes non-reducible, i.e. there is no recapture of the disc while opening the mouth, the clicking reduces in intensity or vanishes.

In the early stages (disc displacement with reduction), patients have been described as having increased range of anterior condylar translation. As the stage of disc displacement without reduction ensues, the patient encounters reduced mouth opening and even locked closed in some cases.

Ref: Mehndiratta A, Kumar J, Manchanda A, et al. Painful clicking jaw: a pictorial review of internal derangement of the temporomandibular joint. Pol J Radiol. 2019;84:e598-e615. Published 2019 Dec 23. doi:10.5114/pjr.2019.92287

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.