Orthodontics Flashcards
7 cards from real DMD practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Orthodontics flashcards as text
Which functional appliance is a fixed device that positions the mandible forward to correct a Class II malocclusion in a growing patient by altering condylar growth?
Answer: Herbst appliance
The Herbst appliance is a fixed functional device that holds the mandible in a protruded position continuously, stimulating condylar adaptation and correcting Class II skeletal discrepancy in growing patients.
The ANB angle in cephalometric analysis directly represents which skeletal relationship?
Answer: Anteroposterior relationship between the maxilla and mandible
The ANB angle (SNA minus SNB) reflects the anteroposterior discrepancy between the maxillary (A point) and mandibular (B point) bases; the norm is approximately 2°.
A patient presents with a unilateral posterior crossbite and an apparent midline shift. Upon opening, the mandibular midline coincides with the maxillary midline. What is the most likely etiology?
Answer: Functional shift caused by a premature occlusal contact
When the midlines align on opening but deviate in centric occlusion, it indicates a functional shift where a premature contact deflects the mandible laterally into a unilateral crossbite position.
The Hyrax rapid palatal expander achieves skeletal expansion of the maxilla primarily through which mechanism?
Answer: Opening of the midpalatal suture to produce true skeletal widening
The Hyrax RPE opens the midpalatal suture through heavy orthopedic forces, producing true skeletal expansion of the maxillary arch — most effective before suture fusion in adolescence.
In orthodontic mechanics, 'anchorage' is best defined as:
Answer: Resistance to unwanted or reactive tooth movement
Anchorage refers to the resistance offered by teeth, bone, or extraoral structures to the reactive (unwanted) forces generated during orthodontic tooth movement.
Which bracket slot dimension is characteristic of the standard edgewise appliance and allows full three-dimensional control of tooth position including torque?
Answer: 0.022 × 0.028 inch slot
The standard edgewise bracket uses a 0.022 × 0.028 inch rectangular slot, which accommodates large rectangular wires that allow precise torque and tip control in three planes of space.
In orthodontic treatment planning, which factor most strongly contraindicates the use of functional appliances for skeletal correction?
Answer: Completion of skeletal growth (closed epiphyses, stable cephalometrics)
Functional appliances rely on redirecting active skeletal growth; once growth is complete, they cannot produce significant skeletal change, making orthognathic surgery the appropriate alternative.