MFDS Part 1 - Membership of Faculty of Dental Surgery Orthodontics and Dentofacial Development Questions and Answers

Question 1

A 13-year-old patient presents for an orthodontic assessment.
The clinical examination reveals a Class II division 1 incisor relationship with an overjet of 7mm.
All other occlusal features are within normal limits.
According to the Index of Orthodontic Treatment Need (IOTN), what is the Dental Health Component (DHC) grade for this patient?

Accepted Answer

4a

Answer

3a

Answer

4d

Answer

5a

Question 2

Which structure of the cranial base completes its growth earliest and is therefore commonly used as a stable reference structure for superimposition in longitudinal cephalometric analysis?

Accepted Answer

Anterior cranial base (Sella-Nasion line)

Answer

Spheno-occipital synchondrosis

Answer

Mandibular symphysis

Answer

Maxilla

Question 3

An Upper Removable Appliance (URA) has been constructed to correct a unilateral posterior crossbite affecting the maxillary first premolars and molars. Which component is essential for providing the force required to achieve the desired buccopalatal expansion?

Accepted Answer

Midline expansion screw

Answer

Z-spring

Answer

Adams clasp

Answer

Southend clasp

Question 4

A 10-year-old patient is reviewed for a routine dental examination. The maxillary right deciduous canine is still present and firm, and the permanent canine is not palpable in the buccal sulcus. A parallax radiographic assessment confirms the permanent canine is palatally displaced. According to UK orthodontic guidelines, what is the most appropriate initial management?

Accepted Answer

Extract the deciduous canine and review eruption in 6-12 months.

Answer

Immediately refer for surgical exposure and bonding of the ectopic canine.

Answer

Place a fixed appliance to create space for the canine.

Answer

Monitor without intervention until the patient is 13 years old.

Question 5

The Twin Block appliance is a widely used functional appliance in the UK for the correction of Class II division 1 malocclusions. What is its primary mode of action in correcting the skeletal and dental relationship?

Accepted Answer

By encouraging mandibular growth and causing dentoalveolar changes.

Answer

By applying extra-oral force to restrain maxillary growth.

Answer

By causing proclination of the lower incisors only.

Answer

By expanding the maxilla and distalising the maxillary molars.

Question 6

Following the completion of comprehensive fixed appliance therapy, which factor is considered a primary contributor to long-term post-treatment relapse, such as late lower incisor crowding?

Accepted Answer

Unfavourable continued facial growth.

Answer

Contraction of the supracrestal gingival fibres.

Answer

Persistent soft tissue pressures (e.g., tongue thrust).

Answer

Inherent memory of the periodontal ligament fibres.