Temporary anchorage devices enable controlled tooth movements such as anterior retraction, molar intrusion/distalization, nonsurgical open‑bite correction, and cant correction with simple placement, immediate loading, and minimal morbidity compared with plates or implants.

🔑 GENERAL PRINCIPLES

• Safe mesiodistal space: ≥ 3 mm between roots
• Safety depth (bone overlying narrowest interradicular area): ≥ 4 mm (ideally matching miniscrew length, 5–7 mm)
• Preferred vertical level: 4 mm from CEJ (attached gingiva zone)
• Anterior regions: Require subapical placement (≥ 6–8 mm from CEJ)
• Posterior regions: Often safe at 4 mm; angulation increases clearance and cortical support
• Placement angulation:
  • Straight/perpendicular in premolar and subapical anterior regions
  • Oblique/angulated in intermolar regions for safety

✅ COLOR LEGEND

• 🟢 SAFE: Adequate mesiodistal space (≥3 mm) & safety depth
• 🟡 CAUTION: Limited space; angulation or subapical placement needed
• 🔴 AVOID: Insufficient space, high root risk

📍 MAXILLA

Region (Teeth)	Level from CEJ	Safety	Notes
Central incisors	8 mm	🟡	Subapical/equiapical only
Lateral incisor – Canine	8 mm	🟡	Narrow at CEJ; safer apically
Canine – 1st premolar	6 mm	🟢	Reliable site
1st – 2nd premolars	4 mm	🟢	Consistently safe
2nd premolar – 1st molar	4 mm	🟢	Best interdental space
1st – 2nd molars	4–6 mm	🟡	Angulated placement advised

📍 MANDIBLE

Region (Teeth)	Level from CEJ	Safety	Notes
Anterior incisors	Any	🔴	Avoid interradicular; only true subapical
Lateral incisor – Canine	4–6 mm	🔴	Space ❤ mm
1st – 2nd premolars	4 mm	🟢	Most reliable site
2nd premolar – 1st molar	4 mm	🟢	Consistently safe
1st – 2nd molars	4–6 mm	🟢/🟡	Safe; angulation may help for group distalization

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Reference:
Lee KJ, et al. Computed tomographic analysis of tooth-bearing alveolar bone for orthodontic miniscrew placement.AJODO. 2009;135:486–94.

🦷 CLINICAL MCQs – Miniscrew Placement (Based on Lee et al., AJODO 2009)

Section A – Clinical MCQs (Single Best Answer)

1. A 25-year-old patient requires intrusion of maxillary central incisors. Based on CT evidence, the safest site for miniscrew placement is:
   a) Between central incisors at 2 mm from CEJ
   b) Between central incisors at 8 mm from CEJ
   c) Between canine and 1st premolar at 2 mm from CEJ
   d) Between 1st and 2nd molars at 2 mm from CEJ
   Answer: b) Between central incisors at 8 mm from CEJ
2. In the maxilla, the largest interdental space was observed:
   a) Between 1st and 2nd premolars at 4 mm
   b) Between 2nd premolar and 1st molar at 8 mm
   c) Between canine and 1st premolar at 2 mm
   d) Between 1st and 2nd molars at 2 mm
   Answer: b) Between 2nd premolar and 1st molar at 8 mm
3. Which mandibular region is considered most reliable for miniscrew placement at 4 mm from CEJ?
   a) Between central incisors
   b) Between 1st and 2nd premolars
   c) Between lateral incisor and canine
   d) Between canine and 1st premolar
   Answer: b) Between 1st and 2nd premolars
4. Miniscrew placement in the mandibular anterior region is best achieved by:
   a) 2–4 mm from CEJ in interradicular space
   b) Subapical placement only
   c) Angulated placement between central incisors
   d) Placement between lateral incisor and canine at 6 mm
   Answer: b) Subapical placement only

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Section B – True / False

1. Interradicular space greater than 3 mm is mandatory for safe miniscrew placement.
   True
2. In the maxillary intermolar region, angulated miniscrew placement is recommended due to large safety depth but limited interroot space.
   True
3. In the mandibular incisor region, sufficient interradicular space (>3 mm) is available at 4 mm from CEJ.
   False
4. Buccal bone thickness is generally greater in posterior regions compared to anterior regions.
   True
5. Panoramic radiographs are equally reliable as CT for identifying miniscrew safe zones.
   False

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Section C – Match the Following

A (Region)	B (Safe placement level / guideline)
1. Maxillary central incisors	a. 8 mm from CEJ (subapical/equiapical)
2. Maxillary 1st–2nd premolars	b. 4 mm from CEJ
3. Mandibular anterior incisors	c. Avoid interradicular; only subapical
4. Mandibular 1st–2nd premolars	d. 4 mm from CEJ (safe site)
5. Maxillary 1st–2nd molars	e. Angulated placement due to large safety depth

Answer Key:
1–a, 2–b, 3–c, 4–d, 5–e