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