ABO Orthodontic Diagnosis and Treatment Planning 3 — Questions and Answers
Question 1: The Wits appraisal is measured by projecting points A and B onto which plane?
- Frankfort horizontal plane
- Functional occlusal plane (Correct answer)
- Mandibular plane
- Palatal plane
Correct answer: Functional occlusal plane
The Wits appraisal drops perpendiculars from points A and B onto the functional occlusal plane.
Question 2: Which of the following is a primary indication for extraction in orthodontic treatment planning?
- Mild spacing
- Severe arch length deficiency with bimaxillary protrusion (Correct answer)
- Class I with ideal overjet
- Single missing lateral incisor with spacing
Correct answer: Severe arch length deficiency with bimaxillary protrusion
Severe crowding combined with dental protrusion often requires extraction to relieve the discrepancy.
Question 3: A steep mandibular plane angle combined with a long lower facial height suggests which growth tendency?
- Horizontal (hypodivergent)
- Vertical (hyperdivergent) (Correct answer)
- Normodivergent
- Transverse deficiency
Correct answer: Vertical (hyperdivergent)
High mandibular plane angle and increased lower face height indicate a hyperdivergent vertical growth pattern.
Question 4: The curve of Spee is best described as:
- The transverse curvature of the arches
- The anteroposterior occlusal curvature seen in lateral view (Correct answer)
- The angulation of individual teeth
- The midpalatal suture orientation
Correct answer: The anteroposterior occlusal curvature seen in lateral view
The curve of Spee is the anteroposterior curvature of the occlusal plane viewed from the side.
Question 5: In a growing Class II patient with a retrognathic mandible, which appliance approach is most appropriate?
- Rapid palatal expander
- Functional appliance to encourage mandibular advancement (Correct answer)
- Anterior bite plate only
- Extraction of lower incisors
Correct answer: Functional appliance to encourage mandibular advancement
Functional appliances harness growth to advance a deficient mandible in growing Class II patients.
Question 6: A crossbite that shifts the mandible laterally on closure is classified as:
- Dental crossbite with no shift
- Functional (pseudo) crossbite (Correct answer)
- Skeletal crossbite only
- Anterior open bite
Correct answer: Functional (pseudo) crossbite
A lateral shift on closure indicates a functional crossbite caused by occlusal interference.
Question 7: Which record is essential for evaluating the transverse dimension and posterior crossbite?
- Lateral cephalogram
- Frontal (PA) cephalogram or study models (Correct answer)
- Bitewing radiographs
- Sialography
Correct answer: Frontal (PA) cephalogram or study models
A posteroanterior cephalogram and study models assess transverse width and posterior crossbites.
ABO Orthodontic Diagnosis and Treatment Planning 3
The Wits appraisal is measured by projecting points A and B onto which plane?