1. Why is the inter-incisor angle critical to stability in Class II div 2?

• Class II div 2 has increased inter-incisor angle
• Excessive angle → deep overbite and mandibular locking
• Normalizing angle:
  • Reduces vertical overlap
  • Allows lower incisors to sit in zone of balance
• Palatal torque of upper incisors is essential
• If angle is not corrected → lower incisors relapse

Viva punchline:
👉 Stable overbite correction depends on normalization of the inter-incisor angle.

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2. Why doesn’t lower incisor advancement relapse?

• Relapse occurs only if teeth move outside muscular envelope
• Lower incisors are advanced:
  • Within lower lip contour
  • Not beyond soft-tissue limits
• Simultaneous:
  • Upper incisor intrusion
  • Palatal torque
• This unlocks the mandible
• New incisor position becomes physiologic

Viva punchline:
👉 Because the lower incisor is advanced within the soft-tissue envelope.

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3. Why is flattening the curve of Spee essential?

• Class II div 2 → exaggerated curve of Spee
• Lower incisor advancement creates:
  • ~4–5 mm space anteriorly
  • ~8–10 mm total
• ~2 mm per side used for:
  • Flattening curve of Spee
• Remaining space used for alignment
• Flattening is part of correction, not space loss

Viva punchline:
👉 Curve of Spee flattening enables non-extraction treatment.

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4. Why upper removable appliance first?

• Achieves multiple goals simultaneously:
  • Bite opening
  • Upper incisor palatal torque
  • Buccal segment distalization
  • Correction of scissor bite
  • Upper incisor intrusion
• Frees mandible from locked position
• Fixed appliance alone cannot do this efficiently

Viva punchline:
👉 Upper removable appliance provides coordinated first-phase correction.

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5. Importance of upper incisor centroid

• Centroid = midpoint of incisor root
• Helps assess:
  • Root position
  • Torque control
• Lower incisor tip position relative to centroid determines:
  • Inter-incisor angle
  • Stability
• Lower incisor behind centroid → unstable
• Slightly ahead → stable relationship

Viva punchline:
👉 Centroid guides stable inter-incisor positioning.

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6. When to extract? Why not first premolars?

• Extractions only if:
  • Severe skeletal discrepancy
  • Inadequate space after leveling
• First premolar extraction:
  • Compromises buccal segment correction
• Second premolars preferred:
  • Maintain Class I molar correction
• Decision after therapeutic diagnosis

Viva punchline:
👉 Extraction decisions are delayed and conservative in Class II div 2.

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7. Why long-term lower bonded retainer?

• Lower anterior relapse is unpredictable
• Tight perioral musculature common
• Lower anterior segment is foundation of correction
• Bonded retainer:
  • Maintains AP and transverse position
• Stable lower incisors support upper incisors
• Upper arch often needs minimal retention

Viva punchline:
👉 Lower bonded retainer ensures long-term stability.

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8. Role of upper incisor–lip relationship

• Upper incisor should:
  • Contact inner slope of lower lip
  • Show 2–3 mm at rest
• Defines soft-tissue boundary
• Dictates:
  • Amount of intrusion
  • Palatal torque
• Aesthetic goal = biomechanical goal

Viva punchline:
👉 Soft-tissue aesthetics guide incisor positioning.

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9. Why no encroachment on lower lip?

• Teeth outside soft-tissue envelope relapse
• Lower lip exerts strong muscular pressure
• Advancing beyond lip contour → instability
• Staying within lip contour ensures:
  • Muscular support
  • Long-term stability

Viva punchline:
👉 Respecting the soft-tissue envelope prevents relapse.

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10. Therapeutic diagnosis and extraction decision

• Therapeutic diagnosis = diagnosis through treatment response
• In Class II div 2:
  • Complete first-phase correction
  • Reassess space and alignment
• Avoid premature extraction decisions
• Especially useful in borderline cases

Viva punchline:
👉 Extraction is decided after observing treatment response.

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