MJDF Orthodontics 1 — Questions and Answers
Question 1: According to Angle's classification, Class II Division 1 malocclusion is characterised by which of the following?
- Proclined upper incisors with increased overjet (Correct answer)
- Retroclined upper central and lateral incisors with deep overbite
- Lower incisor edge occluding with upper incisor palatal surfaces
- Crossbite of the upper first molars
Correct answer: Proclined upper incisors with increased overjet
Class II Division 1 features a distal molar relationship with proclined upper incisors and characteristically increased overjet.
Question 2: What is the normal ANB angle in a balanced skeletal relationship as measured on a lateral cephalogram?
- 0°
- 2–4° (Correct answer)
- 6–8°
- 10–12°
Correct answer: 2–4°
The normal ANB angle is 2–4°, reflecting a typical forward position of the maxilla relative to the mandible.
Question 3: The lower incisor to mandibular plane angle (IMPA) has a UK mean value of approximately:
- 82°
- 87°
- 93° (Correct answer)
- 102°
Correct answer: 93°
The UK mean IMPA is approximately 93° (±6°), reflecting the normal proclination of lower incisors relative to the mandibular plane.
Question 4: Which index is used within the NHS in the UK to assess a patient's eligibility for orthodontic treatment?
- PAR index
- DAI index
- Index of Orthodontic Treatment Need (IOTN) (Correct answer)
- ICON index
Correct answer: Index of Orthodontic Treatment Need (IOTN)
The IOTN grades dental health and aesthetic components and is the standard used by the NHS to determine whether patients qualify for funded orthodontic care.
Question 5: During which stage of dental development is interceptive orthodontic treatment most commonly initiated?
- Primary dentition stage
- Mixed dentition stage (Correct answer)
- Early permanent dentition stage
- Late permanent dentition stage
Correct answer: Mixed dentition stage
The mixed dentition stage is the optimal window for interceptive treatment, allowing early correction before all permanent teeth have erupted.
Question 6: A Class III skeletal relationship is best described by which cephalometric finding?
- ANB angle greater than 4°
- ANB angle of 2–4°
- ANB angle of 0° or less (Correct answer)
- SNA angle greater than 85°
Correct answer: ANB angle of 0° or less
A Class III skeletal pattern is identified by an ANB angle of 0° or below, indicating mandibular prominence relative to the maxilla.
Question 7: What does the Bolton analysis assess in orthodontic treatment planning?
- Available arch length versus total tooth width
- Discrepancy between the overall size of the maxilla and mandible
- Tooth size discrepancy between the upper and lower dental arches (Correct answer)
- The skeletal classification of the patient
Correct answer: Tooth size discrepancy between the upper and lower dental arches
The Bolton analysis compares the sum of mesiodistal widths of upper and lower teeth to identify tooth size discrepancies that would prevent ideal occlusion.
MJDF Orthodontics 1
According to Angle's classification, Class II Division 1 malocclusion is characterised by which of the following?