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

The IOTN DHC is used in the UK to assess the need for orthodontic treatment on dental health grounds. Grade 4 indicates a 'great' need for treatment, which typically qualifies for NHS funding. An overjet greater than 6mm but less than or equal to 9mm is specifically classified as grade 4a.

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

The anterior cranial base, represented cephalometrically by the Sella-Nasion (S-N) line, completes its growth relatively early (around age 7). Its stability makes it an invaluable reference plane for superimposing serial cephalometric radiographs to assess treatment changes and subsequent facial growth. The spheno-occipital synchondrosis is a major growth centre that fuses in the late teens, while the maxilla and mandible undergo significant growth throughout puberty.

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

A midline expansion screw is an active component specifically designed to generate transverse forces to widen the maxillary arch. When activated, it separates the two halves of the appliance, pushing the posterior teeth buccally to correct the crossbite. Adams and Southend clasps provide retention, while a Z-spring is typically used to move a single anterior tooth labially.

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

For a palatally displaced maxillary canine in a 10-13 year old with sufficient arch space, the extraction of the deciduous canine is the recommended interceptive measure. This intervention has been shown to have a significant chance of encouraging the permanent canine to improve its position and erupt successfully without further intervention. Surgical exposure is considered only if this interceptive extraction fails.

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

The Twin Block appliance holds the mandible in a protruded position. This posture is thought to stimulate condylar growth, encouraging the mandible to grow to its full potential. Concurrently, it produces significant dentoalveolar changes, including retroclination of upper incisors and proclination of lower incisors, which contribute to overjet reduction. The overall effect is a combination of skeletal and dental modifications.

MFDS Part 1 Practice Test

MFDS Part 1 Practice Test

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