Most damaging feature of class III malocclusion is:

 # Most damaging feature of class III malocclusion is:

A. Retroclined upper anterior teeth

B. Crowding of lower incisors

C. Deviated path of closure

D. Reduced overbite

The correct answer is D. Reduced overbite.

Deep bite is the most damaging feature of class II malocclusion. Reduced deep bite is the most damaging feature of class III malocclusion.

Most common site for melanotic neuroectodermal tumour of infancy (MNTI) is:

 # Most common site for melanotic neuroectodermal tumour of infancy (MNTI) is:

A. Maxilla

B. Mandible

C. Ethmoid bone

D. Cervical spine

The correct answer is A. Maxilla.

MNTI is an uncommon osteolytic, pigmented neoplasm, primarily affecting the jaws of new born infant. Its origin is linked to neural crest cells. More than 90% occur in the head and neck region especially the anterior part of the maxillary ridge. They appear as rapidly growing, non-ulcerated, darkly pigmented lesions, with a radiographic appearance of an invasive malignant neoplasm. 

Dimensions of inner bow of facebow are:

 # Dimensions of inner bow of facebow are:

A. 0.045’’ and 1.125 mm

B. 0.06’’ and 0.09’’

C. 0.045’’ and 1.25 mm

D. 0.45’’ and 0.71’’

The correct answer is A. 0.045’’ and 1.125 mm

Face bow and 'J' hook are force delivering units of a head gear. The face bow helps in delivering extra oral force to the posterior teeth. It consists of outer bow or whisker bow, inner bow, junction, force generating unit and anchor unit. 

Outer bow: 

• It is made of round stainless steel wire 0.051 or 0.062 inch. 

• It is contoured around the face 

• It may be short, medium or long in relation to inner bow. 

Inner bow: 

• It is made of 0.045 inch (1.125 mm) or 0.052 inch (1.3 mm) round stainless steel wire. 

• Inserts into the round buccal tube on the maxillary first molars. 

Thesis Topic Ideas for MDS Orthodontics

 Thesis and research is a part of MDS curriculum. Here are some good research topics to consider if you are an MDS Orthodontics Resident.

1. Assessment of the relationship between maxillary and mandibular incisors in Class I, Class II, and Class III malocclusions
2. Evaluation of the effectiveness of different treatment modalities for correcting Class II malocclusion in growing patients
3. Comparison of the effectiveness of fixed and removable functional appliances in correcting Class II malocclusion

Hemifacial microsomia is a feature of:

 # Hemifacial microsomia is a feature of:

A. Goldenhar syndrome

B. Crouzon syndrome

C. Treacher Collins syndrome

D. Mandibulofacial dysostosis

The correct answer is A. Goldenhar syndrome.

Hemifacial microsomia is a feature of Goldenhar syndrome. Synonyms for hemifacial microsomia include hemifacial hypoplasia, craniofacial microsomia, lateral facial dysplasia, Goldenhar syndrome, and oculoauriculovertebral dysplasia (OAV) spectrum. 

B is incorrect; Hemifacial microsomia is not a feature of Crouzon syndrome. Patients with Crouzon syndrome characteristically have brachycephaly (short skull front to back), hypertelorism (increased distance between eyes), and orbital proptosis (protruding eyes). 

C is incorrect; Hemifacial microsomia is not a feature of Treacher Collins syndrome. The most common clinical findings in Treacher Collins syndrome are relative underdevelopment or absence of the zygomatic bones, resulting in a small narrow face; a downward inclination of the palpebral fissures; underdevelopment of the mandible, resulting in a down-turned, wide mouth; malformation of the external ears; absence of the external auditory canal; and occasional facial clefts. 

D is incorrect, Mandibulofacial dysostosis is a synonym of Treacher Collins syndrome.

The gene aberrant in dentinogenesis imperfecta is:

 # The gene aberrant in dentinogenesis imperfecta is:

A. Chromosome 4

B. Chromosome 13

C. Chromosome 21

D. Chromosome 24

The correct answer is A. Chromosome 4.

Aberration in chromosome 4 (4q21.3) is associated with Dentinogenesis imperfecta. It encodes dentin specific sialophosphoprotein (DSPP) gene. Deficiency of sialoprotein is also suggested as a causative factor for DI. They are generally tulip shaped. 

Chromosome number              Disease 

1                                               Vanderwoude syndrome

4                                               Dentinogenesis Imperfecta 

4                                               Cherubism

15                                             Marfan's syndrome

19                                             Osteogenesis imperfecta

Deficiency of which vitamin causes glossitis, dementia, rough keratotic areas on skin and gastrointestinal symptoms?

 # Deficiency of which vitamin causes glossitis, dementia, rough keratotic areas on skin and gastrointestinal symptoms?

A. Riboflavin

B. Pyridoxine

C. Niacin

D. Pantothenic acid

The correct answer is C. Niacin.

Pellagra is a disease caused by a lack of the vitamin niacin (vitamin B3). Symptoms include inflamed skin, diarrhea, dementia, and sores in the mouth. Areas of the skin exposed to either sunlight or friction are typically affected first. Over time affected skin may become darker, stiffen, peel, or bleed.

There are two main types of pellagra, primary and secondary. Primary pellagra is due to a diet that does not contain enough niacin and tryptophan. Secondary pellagra is due to a poor ability to use the niacin within the diet. This can occur as a result of alcoholism, long-term diarrhea, carcinoid syndrome, Hartnup disease, and a number of medications such as isoniazid. Diagnosis is typically based on symptoms and may be assisted by urine testing.