🔎 Indications

• Supraerupted molars (commonly due to early loss of opposing tooth)
• Need for posterior intrusion to re-establish occlusion
• Minimally invasive alternative to surgery, headgear, or prosthetic crown reduction

🛠 TAD Design

• Material: Titanium alloy
• Size: 6–12 mm length, 1.2–2.0 mm diameter
• Fixation: Mechanical grip to cortical bone (not osseointegrated)
• Placement:
  • Minimally invasive
  • Often only topical anesthesia
  • Inserted through gingiva into bone with hand driver
  • Optional: mucosal punch/pilot hole in thick tissue or dense bone
• Loading: Immediate
• Removal: Simple hand unscrewing
• Failure rate: 9–30%

🔩 Types of TADs

1. Self-tapping

• Conical design, threaded shaft, tapered tip
• Requires pilot hole → then inserted with hand driver

2. Self-drilling

• Corkscrew design, threaded shaft, sharp tip
• Cuts through bone, expels debris
• Placed directly with hand driver (no pilot hole)

👩‍⚕️ Patient Selection

• ≥ 12 years (FDA approved)
• Avoid: growing patients (palatal suture), heavy smokers, bone metabolic disorders

Optimal Placement

• Maxilla:
  • Between 2nd premolar & 1st molar (5–8 mm from alveolar crest)
  • Angle: 30–45° to occlusal plane (posterior region)
  • Palatal slope (avoid greater palatine nerve)
  • Midpalatal region = D1/D2 bone
• Mandible:
  • Either side of 1st molar (~11 mm from crest)
  • Angle: 30–45° to occlusal plane
• Bone Density (Misch classification):
  • Best: D1–D3 (dense cortical, anterior regions, palatal, posterior mandible)
  • Avoid: D4 (tuberosity – failure rate up to 50%)
  • Mnemonic: “One Oak, Two Pine, Three Balsa, Four Foam”
• Soft Tissue Health
  • Better: Keratinized (attached) tissue → ↓ failure
  • Worse: Nonkeratinized mucosa → gingival inflammation, overgrowth
  • Tip: In buccal posterior, if risk of root proximity → place in alveolar mucosa

Type	HU Range	Location	Analogy	TAD Suitability
D1	>1250 HU	Anterior mandible, buccal shelf, midpalatal	Oak 🌳	✔ Best, may need pilot hole
D2	850–1250 HU	Ant. maxilla, midpalatal, post. mandible	Pine 🌲	✔ Good
D3	350–850 HU	Post. maxilla & mandible (thin cortex)	Balsa wood	✔ Acceptable
D4	150–350 HU	Tuberosity region	Polystyrene foam	❌ High failure (35–50%)

Bone Availability (Safe Zones)

Region	Best Site	Distance from Crest
Maxilla (posterior)	Between 2nd premolar & 1st molar	5–8 mm
Mandible (posterior)	Either side of 1st molar	~11 mm
Anterior (maxilla & mandible)	Between canine & lateral incisor	—

If inadequate space:

• Palatal placement
• Root divergence before insertion

Insertion Technique

Region	Angle of Insertion	Rationale
Posterior Maxilla	30°–45° to occlusal plane	Cortical anchorage; balance safety & stability
Anterior Maxilla / Posterior Edentulous Maxilla	~90° to occlusal plane (parallel to sinus floor)	Avoid sinus perforation, biomechanically better for molar intrusion
Mandible	30°–45° to occlusal plane	Greater contact with thick cortical bone

🔹 Tip: Orthodontic wire surgical stent may be used to guide accurate insertion

Force Loading Guidelines

Condition	Recommended Force	Notes
General loading limit	≤ 300 g	Beyond this = risk of failure
Thin cortical bone	~50 g	(Dalstra)
Dense mandibular bone	Stable up to 900 g	(Buchter)
Maxillary molar intrusion (children)	90 g	(Kalra)
Maxillary molar intrusion (adults)	50 g	(Melsen)
Miniscrew-supported max molar intrusion	100–200 g	Optimal range
En-masse intrusion (PM2 + M1 + M2)	200–400 g/side	Requires more force
Miniplate-supported mand molar intrusion	500 g	(Umemori)

Post-Insertion Care

Chlorhexidine Rinse (0.12%)

• 10 mL BID for 1 week (continue if needed)
• Prevents soft tissue inflammation & overgrowth
• Slows epithelialization → keeps miniscrew head accessible

⚠️ Important Instruction for Patients:

• Wait 30 min after rinsing before brushing with fluoridated toothpaste (to avoid inactivation of chlorhexidine by anionic agents in toothpaste).

Technique	Placement	Control of Tipping	Notes
Single TAD	Buccal dentoalveolus (between PM2 & M1 at mucogingival junction)	Transpalatal arch (TPA) with buccal root activation	TPA raised 3–5 mm → tongue pressure aids intrusion
Two TADs	Buccal: between M1 & M2 Palatal: slope between PM2 & M1 (medial to greater palatine nerve)	Elastic chain / NiTi coil passes diagonally across occlusal table	Risk of palatal tipping → may need partial braces
Palatal / Midline	Midline or palatal slope if interradicular space inadequate	Extension arm to reach slope; partial braces for control	Used when buccal bone insufficient

Intrusion Rates

• Single M1 intrusion → 3–4 mm in ~6–8 months
• M2 intrusion → 1–2 mm in ~5 months
• En-masse PM2 + M1 + M2 → ~0.5 mm/month

Root Resorption Risks

• Mechanism: Intrusive force concentrates at apex → PDL compression → possible necrosis & resorption
• Evidence:
  • Molars = second highest risk (after incisors)
  • Documented in molars with:
    • Tip-back mechanics
    • High-pull headgear intrusion
    • Distalization forces
  • Range: 25–240 g can cause histologic resorption (Reitan)
• Controversy:
  • Some studies show no significant difference between light (50 g) vs heavy (200 g) forces in resorption risk (Owman-Moll)
  • Ari-Demirkaya et al. → Mean apical resorption only 0.18 ± 0.18 mm after 7 months
  • Comparable to conventional orthodontics → not clinically significant
• Sinus floor effects:
  • Intruding palatal root may lift sinus floor membrane intranasally
  • Usually without complications

Risks & Complications

Complication	Clinical Note	Management / Prognosis
Root trauma	Injury to PDL/root → possible vitality loss or ankylosis	If no pulp involvement → repair in 3–4 months
Anchorage failure	Miniscrews may loosen, tip, or extrude	Mobile screw → must be replaced; usually due to thin cortical bone or excessive force
Soft tissue irritation	More common in loose alveolar mucosa → inflammation, overgrowth, ulcers	Prefer keratinized tissue; hygiene + CHX rinse
Nerve injury	Greater palatine nerve risk in palatal slope (5–15 mm from gingival border, lateral to M2/M3)	Careful site selection & angulation
Sinus perforation	Small (<2 mm) usually self-heals, no effect on stability	Large perforation → possible sinusitis or oroantral fistula
Relapse	Extrusion of intruded molars common	Average relapse ≈ 30%