As orthodontic students, you’re entering the field at an exciting time of technological innovation. Traditional thermoformed aligners have revolutionized orthodontic treatment, but now we’re witnessing the emergence of direct 3D-printed aligners that promise to transform the way we approach clear aligner therapy.

Understanding Direct 3D-Printed Aligners

Direct 3D-printed aligners are fabricated using specialized photopolymer resins, with Tera Harz TC-85 being the most prominent FDA-approved material. Unlike traditional aligners that are vacuum-formed over printed models, these aligners are printed directly as complete shells, offering unprecedented design flexibility and customization possibilities.

Revolutionary Design Capabilities

What sets direct 3D-printed aligners apart is their unlimited design possibilities. As future orthodontists, you’ll have the ability to:

Fine-tune biomechanics by adjusting the thickness at any part of the aligner, enabling precise force delivery and production of countermoments for root movement. This level of customization was previously impossible with conventional thermoformed aligners.

Incorporate specialized features such as:

• Cutouts and bite ramps for specific clinical situations
• Class II advancement wings similar to functional appliances
• Integrated tubes for TMA spring insertion in cases requiring gap closure after relapse
• Hooks for elastics built directly into the aligner design
• Pressure columns for extrusion movements, eliminating the need for attachments
• Customized trim lines for optimal retention and comfort

Material Properties and Clinical Advantages

Shape Memory Technology

The most remarkable feature of TC-85 resin is its shape memory capability. After exposure to high temperatures, aligners can be deformed to easily snap over undercuts, but when maintained in the oral environment (above 30°C) for the prescribed 22 hours daily, any deformation self-corrects. This property ensures consistent force delivery throughout the treatment period.

Force Delivery Characteristics

Research demonstrates that direct 3D-printed aligners apply continuous, light forces due to their unique viscoelastic properties. Studies show that force levels during extrusion movements are significantly lower compared to thermoformed aligners, potentially reducing patient discomfort and unwanted side effects.

The ability to customize thickness at different aligner regions allows for better force distribution, optimizing tooth movement while minimizing adverse effects. This represents a significant advancement in biomechanical control that you’ll appreciate in your clinical practice.

Durability and Performance

TC-85 aligners maintain their mechanical properties for at least one week of intraoral use. Unlike thermoplastic aligners, they can remain at body temperature without losing force from deformation, ensuring consistent treatment progression. However, surface roughness and porosity increase after one week of wear, similar to conventional aligners.

Workflow Steps

1. Digital Setup & Staging
   – Software platforms (e.g., Graphy DAD)
   – Movement limits: 0.25–0.30 mm per tooth; ≤2° angulation
2. 3D Printing
   – 6–8 aligners per run (30–60 min)
3. Cleaning & Support Removal
   – Centrifuge 6 min; manual support removal
4. Post-Processing
   – UV cure (17–25 min in N₂); polish; ultrasonic clean

Software Tools

• Graphy Direct Aligner Designer (free)
• Commercial: 3Shape, Blue Sky Plan, NemoStudio

📌 Source: Ludwig B, Ojima K, Schmid JQ, Knode V, Nanda R. Direct-Printed Aligners: A Clinical Status Report. J Clin Orthod. 2024;58(11):658–668

CVM Basics

• Vertebrae used: C2, C3, C4
• Visible on lateral cephalogram (no extra radiation)
• Traditionally used to estimate skeletal maturity & mandibular growth peak

CVM Stages (Baccetti et al.)

• CS1 – Inferior borders of C2–C4 flat; bodies trapezoidal.
• CS2 – Concavity begins at C2 lower border.
• CS3 – Concavity at C2 & C3; bodies less trapezoid.
• CS4 – Distinct concavities at C2–C4; bodies nearly rectangular.
• CS5 – Strong concavities; square vertebrae.
• CS6 – Deep concavities; taller than wide.

CVM Shape Changes with Age

• C2–C4 Inferior Borders → Concavity increases with age
• C3 & C4 Height → Becomes taller, shape transitions trapezoid → rectangular/square
• Sex Difference: Girls reach each stage earlier than boys

Study Findings (Gray et al., 2016)

✅ Morphometric changes match classic CVM descriptions
❌ CVM stages did not reliably predict mandibular growth peak
👉 Growth peak often occurred before or after CS3, not always between CS3–CS4

Peak mandibular growth: typically occurs around CS3, but study shows high variability:

• 32% after CS3
• 28% after CS1
• 20% after CS2
• 20% after CS4
• No growth peak at CS5 or CS6

Clinical Pearls

• CVM can confirm if peak growth has passed, but
• Chronologic age is often a better predictor than CVM alone
• Always combine with:
  • Secondary sex characteristics
  • Height/weight velocity
  • Dental development
  • Clinical growth indicators

📌 Quick Rule of Thumb

• Before CS3 → Growth spurt may still be coming.
• At CS3 → Possible growth peak (but variable).
• After CS4 → Growth peak has passed.

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Clinical MCQs – Cervical Vertebrae & Mandibular Growth

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Q1.

A 12-year-old boy presents for orthodontic evaluation. His lateral cephalogram shows concavity in the inferior borders of C2 and C3, but not yet in C4. The vertebral bodies are less trapezoid, approaching rectangular.
What can be inferred about his mandibular growth peak?

A. Growth peak is most likely already passed
B. Growth peak is occurring now or will occur soon
C. Growth peak cannot occur at this stage
D. Growth peak will only occur at CS5–CS6

Answer: B
Explanation: Concavities at C2 and C3 correspond to CS3, which is often associated with the timing of peak mandibular growth. However, variability exists (some peak after CS1, CS2, or CS4).

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Q2.

During a growth assessment, a girl’s cephalogram shows all three cervical vertebrae (C2–C4) with distinct concavities, and the vertebral bodies appear rectangular and taller. She is 14 years old.
What is the most likely clinical implication?

A. She is approaching mandibular growth peak
B. She is currently at growth peak
C. She has already passed mandibular growth peak
D. She will have another growth spurt at CS6

Answer: C
Explanation: Distinct concavities and rectangular vertebrae (CS4 or later) suggest the growth peak has passed.

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Q3.

Which of the following statements best reflects the findings of the study?

A. CVM staging alone is a reliable predictor of mandibular growth peak
B. Morphometric analysis can clearly differentiate “before” and “during” mandibular growth peak
C. Chronologic age is a better predictor of mandibular growth peak than CVM stage
D. Mandibular growth always occurs after CS3

Answer: C
Explanation: The study found chronologic age correlated more consistently with mandibular growth than CVM staging. Morphometric differences were only clear after the peak, not before vs during.

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Q4.

An orthodontist uses CVM staging to plan functional appliance therapy in a boy. His CVM stage is CS3. According to the study, what percentage of children actually reach peak mandibular growth after CS3?

A. 20%
B. 28%
C. 32%
D. 50%

Answer: C
Explanation: Only 32% of participants reached peak mandibular growth after CS3, highlighting variability.

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Q5.

Which of the following sex differences were observed in the study regarding mandibular growth peak timing?

A. Boys reached peak earlier (mean 11.7 yrs) than girls (mean 12.8 yrs)
B. Girls reached peak earlier (mean 11.7 yrs) than boys (mean 12.8 yrs)
C. No sex differences were found in timing of growth peak
D. CVM stage timing was identical in both sexes

Answer: B
Explanation: Girls reached mandibular growth peak earlier (mean 11.7 years) than boys (12.8 years).

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So, we’ve all sat through those ortho lectures where the professor keeps throwing around terms like “external root resorption” and “tooth-borne versus bone-borne expanders,” and honestly, at first, it feels like way too much. But here’s the simple breakdown of what’s actually happening.

Rapid Maxillary Expansion (RME) is used to fix transverse maxillary deficiency. The problem? The forces aren’t exactly gentle—they’re around 0.9 to 4.5 kg—and sometimes your roots pay the price. That’s where ERR (External Root Resorption) comes in.

Now, there are two main types of expanders:

• Tooth-borne (Hyrax type): All the force is on the teeth.
• Bone-borne (MARPE type): Screws in the palate take the load instead.

Now, how do we actually see ERR? That’s where CBCT comes in. It’s almost as accurate as micro-CT (which is super precise but can only be used on extracted teeth). Studies using CBCT showed that first molars (M1) and first premolars (P1) lose root volume after expansion, and even second premolars (P2) — the ones not holding the appliance — can get affected too. Forces spread everywhere!

Here’s the important point: most studies only looked at ERR right after expansion. But remember, cementum can repair itself a bit over time. So if you only check right away, you might overestimate the “permanent” damage. That’s why this study looked at ERR after 6 months of retention — to see what happens once the dust settles.

Here’s what the research shows:

• Tooth-borne RME → more ERR. First molars lose the most root volume (around 17 mm³), followed by premolars. Even second premolars, which aren’t directly attached, still show resorption.
• Bone-borne RME → less ERR. Molars only lose about 3 mm³. There’s still some resorption, but it’s way less compared to tooth-borne.

📊 Findings (6-month post-retention, CBCT-based)

Tooth	ERR Volume Loss (mm³)	TB Group	BB Group
M1 (1st molar)	Highest	17.03	3.11
P1 (1st premolar)	Moderate	6.42	1.04
P2 (2nd premolar)	Least	5.26	1.24

• All teeth showed ERR (anchored + unanchored).
• M1 palatal root most affected in length shortening.
• ERR localized to apical, bucco-apical & bucco-medial areas.
• Greater in TB vs. BB, but differences clinically questionable.
• Mechanism of ERR: The buccal forces from the RME appliance compress the periodontal ligament, leading to tissue hyalinization. ERR occurs during the subsequent removal of this necrotic tissue on the compressed (buccal) side of the root. The root apex is also a sensitive area due to high force concentration and denser bone.

⚠️ Clinical Insights

• ERR occurs in both abutment and non-abutment teeth.
• Amount of root shortening (~0.3 mm) unlikely to affect longevity.
• Bone-borne expanders ↓ ERR risk but do not eliminate it.
• Cementum repair may occur post-retention.

📖 Citation

Leonardi R, Ronsivalle V, Barbato E, Lagravère M, Flores-Mir C, Lo Giudice A.
External root resorption and rapid maxillary expansion: TB vs BB comparison at post-retention.
Progress in Orthodontics. 2022; 23:45.

Why is Expansion Challenging in Adults?

• Sutural resistance is much stronger due to interdigitation.
• Main resistance sites:
  • Zygomatic buttress
  • Pterygopalatine suture
  • Midpalatal suture

👉 Viva Q: What are the main resistance structures?
✔️ A: Zygomatic buttress, pterygopalatine suture, midpalatal suture.

Conventional Approaches

SARPE (Surgically Assisted Rapid Palatal Expansion)

• Weakens sutures via osteotomies.
• Allows expansion in adults.
• Produces V-shaped expansion (more anterior widening).
• Invasive: hospitalization + morbidity.

👉 Contrast Viva: SARPE vs Tooth-borne RPE

• Both → V-shaped expansion.
• SARPE works in adults; RPE only in growing patients.
• SARPE invasive; RPE non-invasive.

Revolution with TADs

MARPE (Microimplant-Assisted Rapid Palatal Expansion)

• Miniscrews placed anterior palate (thick bone)
• More anterior/inferior expansion than posterior/superior
• Fewer dental side effects vs RPE

👉 Viva Q: Why does MARPE show more anterior expansion?
✔️ Because implants are anterior to posterior resistance sites.

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MSE (Maxillary Skeletal Expander)

• Developed by Won Moon (2003)
• Posterior + superior force application
  • Acts on zygomatic buttress, pterygopalatine & midpalatal sutures
• Design:
  • 4 microimplants (Ø 1.5–1.8 mm × 11 mm)
  • Bicortical engagement (palatal + nasal cortex)
• Effects:
  • Parallel skeletal expansion (not V-shaped)
  • Minimal tipping/lateral rotation
  • Nasal cavity expansion → improved airway
  • Stability proven up to 5 years

👉 Contrast Viva: MARPE vs MSE

• MARPE: anterior implants, anterior/inferior expansion, may allow tipping
• MSE: posterior bicortical implants, parallel expansion including posterior & superior, minimizes tipping

Indications (MARPE/MSE)

✅ Skeletally mature patients with narrow arch
✅ Bilateral posterior crossbite
✅ Nasal airway obstruction
✅ Non-surgical alternative to SARPE
✅ Need for posterior/superior nasal cavity expansion

Contraindications

❌ Poor posterior palatal bone quality
❌ Active periodontal disease
❌ Palatal bone <4 mm
❌ Poor compliance
❌ Medical contraindications to minor surgery

APPLIANCE COMPONENTS of MARPE

• Jackscrew: Positioned between maxillary first molars
• Microimplants: Four implants (1.5-1.8mm Ø, 11mm length)
• Engagement: Bicortical (palatal + nasal cortex)
• Framework: Rigid design for parallel expansion

PLACEMENT PROTOCOL of MARPE

• Pre-op CBCT for bone thickness
• Site: T-zone (distal to 3rd rugae, 2nd premolar region)
• Align force vectors toward zygomatic buttress (center of resistance)
• Tight adaptation to palatal vault
• Ensure bicortical penetration

👉 Viva Q: Why is MARPE positioned anterior to the soft palate (T-zone)?
✔️ To direct forces through the palatal vault toward the zygomatic buttress, optimizing skeletal expansion and reducing tipping.

The MSE was specifically designed to apply expansion force more posteriorly against the zygomatic buttress bones and pterygopalatine sutures, and more superiorly against the midpalatal suture and superiorly positioned perimaxillary suture

VIVA:  Why is MARPE positioned anterior to the soft palate

The MARPE appliance is sited anterior to the soft palate—in the T-zone at the level of the second premolars—so that its miniscrews deliver force vectors through the palatal vault directly toward the zygomatic buttress, optimizing skeletal expansion and minimizing dental tipping. With expansion, a lateral force is applied directly to the midplatal suture medial to the zygomatic buttress. This force distribution promotes more even expansion anteroposteriorly

Biomechanical Rationale:
The zygomatic buttress is the center of resistance of the maxillary complex during transverse expansion. Positioning MARPE miniscrews in the T-zone aligns the force vector with this buttress, shortening the moment arm to skeletal resistance points and producing more parallel, translational movement of the maxillary halves rather than rotational tipping of the alveolar processes or teeth.

T-Zone Landmark:

• Defined by Poorsattar-Bejeh Mir et al. as the area distal to the third rugae, corresponding clinically to the second premolar region in the anterior palate.
• This zone offers maximal palatal bone thickness with minimal soft tissue height, ensuring bicortical engagement and implant stability.

Viva Question: How does having a fulcrum near the frontozygomatic sutures influence hemi-midface movement during maxillary expansion with an MSE?

The amount of lateral rotation seen with an MSE is associated with the archial movement of the hemi-midface, with a fulcrum near the frontozygomatic sutures

With a high‑lateral fulcrum at the frontozygomatic region, the hemi‑midface opens like a fan around that pivot, producing outward archial rotation of the zygomatico‑maxillary block and relatively parallel separation of the maxillary halves

Viva Question: Explain how dual cortical support of microimplants reduces internal strain at the implant neck.

One‐line Answer
“Engaging both palatal and nasal cortical plates at the implant neck and apex distributes load across two dense bony layers, minimizing microimplant neck bending and internal strain.”

Biomechanical Explanation

When a microimplant is bicortically engaged, its neck is stabilized by the thin palatal cortical plate while its apex is anchored in the thicker nasal (or floor) cortical plate. Under lateral expansion forces, this dual‐plane engagement creates a load path through two rigid cortices rather than a single bone interface. Consequently, bending moments and shear stresses at the implant neck are significantly reduced, decreasing risk of neck‐plate microfracture and implant loosening.

ACTIVATION PROTOCOL

Phase	Rate	Duration	Endpoint
Initial	0.5-0.8mm daily	Until diastema appears	Midline separation
Maintenance	0.2-0.27mm daily	Until adequate expansion	Max width > Mand width

SUCCESS INDICATORS

• ✓ Midline diastema formation
• ✓ Patient reports breathing improvement
• ✓ Parallel sutural opening on CBCT
• ✓ Stable implants (no mobility)
• ✓ Manageable pain/swelling levels

RETENTION PROTOCOL

• Keep MSE body as skeletal retainer (6+ months)
• Remove expansion arms after space closure
• Immediate orthodontic space closure recommended
• Long-term stability documented up to 5 years

TROUBLESHOOTING

Problem	Solution
Implant failure	Check bicortical engagement
Asymmetric expansion	Verify implant stability
Excessive pain	Reduce activation rate
No diastema	Re-evaluate bone maturity
Tissue inflammation	Normal healing response

Maxillary constriction is a common problem we face in orthodontics. In younger patients, rapid palatal expansion (RPE) works beautifully because the midpalatal suture is still immature and repairs predictably. But in adults, things get tricky. Conventional RPE is often insufficient, and that’s where miniscrew-assisted rapid palatal expansion (MARPE)comes in.

A recent study by Naveda et al. (2022) looked into how the midpalatal suture actually repairs in adults after MARPE. And the findings are important for how we plan retention and manage expectations in this age group.

🦴 Midpalatal Suture Repair (16 months post-MARPE)

• Incomplete repair common in adults
• Bone density ↓ (vs. pre-expansion):
  • Anterior: –34%
  • Median: –77%
  • Posterior: –52%
• Anterior region always repaired (100%)
• Middle third = weakest (57% unrepaired)
• >50% repair in 81% of patients

📊 Repair Scoring (0–3 scale)

Score	Description	Frequency
0	No repair	0%
1	<50% repair	19%
2	>50% repair	38%
3	Complete repair	43%

🔑 Clinical Takeaways

✔ Expect slower & incomplete repair in adults
✔ Anterior + posterior heal better (vascular supply)
✔ Middle third caution → miniscrew zone, less vascularity
✔ Always reinforce retention

🔒 Retention Protocol

• Maintain expander in situ: 12 months
• After removal → place 0.8 mm stainless steel TPA
• Monitor with CBCT + visual scoring
• Inform patients: repair ≠ full ossification even after 16 months

🔎 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%

Anterior open bite has always been one of the most challenging malocclusions to treat. Patients often present with esthetic concerns, speech difficulties, and compromised function. While orthognathic surgery is a definitive option for severe skeletal open bites, not all patients are candidates—or willing—for surgery. Fortunately, nonsurgical strategies can offer promising results when case selection is appropriate.

🔍 Understanding the Problem

Open bite malocclusion can be dental or skeletal in origin:

• Dental open bite:
  ▸ Normal craniofacial pattern
  ▸ Proclined incisors, under-erupted anterior teeth
  ▸ Often linked to habits like thumb/finger sucking
• Skeletal open bite:
  ▸ Long face syndrome, ↑ mandibular plane angle, retrognathic mandible
  ▸ Greater vertical growth pattern
  ▸ More difficult to manage without surgery

Key Diagnostic Tools

• UAFH : LAFH ratio (<0.65 → poor prognosis for orthodontics)
• Overbite Depth Indicator (ODI)
  ▸ Mean: 74.5°
  ▸ ≤65° → open bite tendency

Treatment Approaches

A. Dental Open Bite

• Extractions & retraction (first premolars) → “drawbridge effect” closes the bite by uprighting incisors.
• Best suited for patients with:
  ✅ Proclined incisors
  ✅ Minimal gingival display
  ✅ ≤2–3 mm incisor show at rest

B. Skeletal Open Bite (Nonsurgical Options)

Skeletal open bite is much harder to correct nonsurgically than dental open bite. The central challenge lies in controlling vertical dimension—particularly by preventing or reducing molar eruption.

Goals: prevent posterior extrusion, allow anterior bite closure.

⚖️ Key Treatment Principles

• Prevent extrusion of upper posterior teeth
• Prevent eruption of lower molars
• Maintain or create a curve of Spee
• ❌ Avoid Class II & III elastics (encourage posterior extrusion)
• ❌ Avoid anterior vertical elastics (incisors already over-erupted)
• Posterior extractions preferred if needed (e.g., caries, premature contact, etc.)

👉 Clinical insight: For every 1 mm molar intrusion, you can achieve about 3 mm anterior bite closure through mandibular counterclockwise rotation.

Method	Key Points
High-pull headgear, lingual arches, bite blocks	Prevent molar eruption; maintain curve of Spee.
Implants / Miniplates	Posterior intrusion (3–5 mm possible); counterclockwise mandibular rotation.
Multiloop Edgewise Archwire (MEAW) Multilooped .016 × .022 SS wires + heavy anterior elastics	Molar intrusion + incisor extrusion; alters occlusal plane; mainly dentoalveolar effects. Not ideal in patients with already excessive dentoalveolar height.
Passive Posterior Biteblocks extend 3–4 mm beyond rest position	Inhibit molar eruption; Restrict buccal dentoalveolar eruption → allow mandibular autorotation forward, hence more effective in growing patients; can be spring-loaded or magnetic (more effective; ~3 mm improvement vs 1.3 mm for spring type)
Functional Appliances – Open bite is worsened by faulty orofacial muscle posture.	FR-4 (Frankel regulator): Alters dentoalveolar eruption, retracts incisors. Some evidence of forward mandibular rotation. Bionator/Activator: Restricts maxillary molar eruption, mild decrease in facial height (~1.3 mm). Used mainly in Class II with mild anterior open bite, not severe skeletal cases.
Active Vertical Corrector (AVC) – using samarium cobalt magnets embedded in acrylic.	Magnetic molar intrusion; worn 12–24 hrs; ~3 mm bite closure avg, bulky (7 mm interocclusal opening needed)
Vertical Pull Chincup	Useful for patients with excessive vertical dimension and backward mandibular rotation tendencies. ↓ mandibular plane angle, restricts molar extrusion; compliance dependent.
Glossectomy	Only in true macroglossia cases. If tongue is normal in size but thrusting, it often adapts after bite closure → surgery not needed. If tongue is truly enlarged relative to oral cavity → partial glossectomy may improve stability.

🔄 The Retention Challenge

One of the biggest hurdles in open bite management is long-term stability.

• Studies show relapse rates of 35–43%.

• Relapse is often due to dentoalveolar rebound rather than skeletal relapse.

• Retention strategies:

  • Long-term/fixed retainers

• • Retainers with occlusal coverage to limit molar eruption

• • Tongue crib when tongue posture is contributory

DOWNLOAD THE PAPER HERE:

SPOTIFY EPISODE LINK: https://creators.spotify.com/pod/profile/dr-anisha-valli/episodes/Nonsurgical-Management-of-Anterior-Open-Bite-e376eng

Anterior open bite is one of the trickiest malocclusions we deal with in orthodontics. It’s not just about teeth — skeletal, dental, functional, and even habitual factors play a role.

🔹 Traditional Approaches

For decades, open bites in adults were often corrected by:

• Extruding anterior teeth orthodontically (which works dentoalveolarly but doesn’t do much for facial esthetics in skeletal cases).
• Orthognathic surgery (Le Fort I osteotomy, sometimes two-jaw surgery) to reposition the maxilla.

These surgical approaches improve facial esthetics but come with a catch — relapse.

• Denison et al. found a 21% relapse at 1-year post-surgery.
• Proffit et al. reported 7–12% overbite reduction within 3 years after Le Fort I surgery.

🔹 The Game Changer: Skeletal Anchorage

With the introduction of absolute anchorage (miniscrews, miniplates), things got exciting. Now, orthodontists could correct open bites without surgery, by intruding the posterior teeth and letting the mandible autorotate upward and forward.

• Kuroda et al.: Skeletal anchorage makes open-bite treatment simpler than surgery.
• Sugawara et al.: Used miniplates to intrude mandibular molars; reported ~30% relapse after 1 year.
• Lee & Park: Miniscrew intrusion of maxillary molars → only 10.4% relapse in molars and 18.1% relapse in overbite at 1 year.

🛠️ How Was Intrusion Done?

Two different miniscrew protocols were used:

1️⃣ Buccal + Palatal Screws

• Screws placed between roots of 2nd premolar–1st molar and 1st–2nd molar.
• Intrusive force applied with elastomeric chains after 1–2 weeks.

2️⃣ Buccal Screws Only

• Screws placed on buccal side at the same sites.
• Rigid transpalatal arch (TPA) added to prevent buccal tipping.

🔹 Maxillary vs. Mandibular Intrusion

• Umemori & Sugawara: Intruded mandibular molars → ~30% relapse in 1 year.
• Current study (Baek et al.): Intruded maxillary molars, since excessive eruption in that region often drives open bite
• ✅ Result: More fundamental correction compared to mandibular intrusion.

🔹 Measuring Stability Correctly

• Past studies measured incisal overlap directly, but this can be misleading when the mandible rotates during treatment.
• This study used new reference planes (HP & VP, based on SN line) to get more accurate and reproducible data.

🔹 Skeletal & Dental Changes Observed

• During treatment:
  • Mandible rotated counterclockwise → bite closure.
  • Pogonion moved forward & upward.
  • Facial height decreased.
  • Some anterior extrusion also helped deepen overbite.
• During retention:
  • Relapse → molar eruption, clockwise rotation, pogonion downward/backward.
  • BUT interestingly, maxillary incisors erupted slightly between year 1–3, which compensated for some relapse and deepened the bite again.

🔹 Relapse Pattern

• Most relapse (>80%) happened in the first year.
• After year 1, changes were minimal.
• Relapse mechanisms resembled orthognathic surgery relapse: molar eruption + mandibular clockwise rotation.
• Interpretation: It’s not just teeth—it’s also muscles & soft tissue adaptation trying to return to “old balance.”

🔹 Role of Retention & Soft Tissue

• Tongue posture, perioral muscles, and habits play a huge role.
• Myofunctional therapy after treatment improves stability.
• Standard retainers (lingual + circumferential) aren’t enough for intruded molars — because intrusion is inherently less stable than tipping or mesiodistal movement.
• Authors suggest an “active retainer”: clear retainer with buccal buttons that can be hooked to miniscrews with elastics to hold molars in place.

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Managing skeletal anterior open bite (AOB) is one of the trickiest problems you’ll see in clinic. Decisions about which teeth to extract — or whether to extract at all — can change the vertical facial pattern, molar position, and ultimately whether the mandible rotates closed (helpful) or stays/re-rotates open (problematic). Understanding how extraction pattern, tooth movement, and growth stage interact helps you plan smarter treatments and set realistic expectations.

The study in one line

A prospective cephalometric study compared vertical/rotational changes in AOB patients treated with three extraction patterns: first premolars (E4), second premolars (E5), and first molars (E6) — and found that extraction choice (plus how posterior teeth move) influenced mandibular rotation. 

1. Extraction Choice & Mandibular Rotation

Extraction Pattern	Skeletal Open Bite Involvement	Effect on Mandibular Rotation
1st Premolars (E4)	Anterior teeth only	No significant rotation.
2nd Premolars (E5)	Extends to posterior teeth	Closing rotation
1st Molars (E6)	Extends to posterior teeth	Greatest closing rotation

The logic behind those findings comes down to three biomechanical factors:

1. Where the extraction space is (anterior vs. posterior in the arch)
2. How molars move to close that space (translation vs. extrusion)
3. How that movement interacts with mandibular rotation mechanics

2. Posterior Tooth Movement & Extrusion

• E4: Greatest posterior tooth extrusion → prevents mandibular rotation.
  • The more teeth you move forward, the harder it is to prevent some extrusion of molars during protraction (especially without TADs or intrusion mechanics).
• E5: Limited posterior extrusion → rotation occurs.
  • This shorter movement path makes vertical control easier — fewer teeth to drag along, less tendency for extrusion.
  • Reduced extrusion allows the posterior occlusal contacts to move out of the “palatomandibular wedge” and encourages mandibular closing rotation (SN–GoGn, SGn–NBa decrease).
• E6: Large forward movement of molars with minimal extrusion → maximum rotation.
  • Posterior occlusal “block” is eliminated quickly, and molars protract mostly horizontally rather than extruding.
  • With posterior teeth moving forward and out of the wedge, the mandible is free to rotate up and forward the most.

3. Cephalometric Change Patterns

Variable	E4	E5	E6
SN–GoGn	↔ (no change)	↓	↓↓ (largest decrease)
SGn–NBa	↔	↑	↑↑
ANS–Me / Na–Me	↑↑ (largest increase)	↑	↑ (smallest)
Upper Molar–Palatal Plane	↑↑	↑	↑
Lower Molar–Mand. Plane	↑↑ (largest)	↑	↑

4. Clinical Tips

• For AOB limited to anterior teeth: First premolar extraction may not help rotation—consider vertical control strategies.
  • Use gable bends, TADs for anchorage/vertical control, intrusion mechanics if needed.
  • Avoid mechanics or auxiliaries that encourage molar extrusion during space closure.
• For AOB involving posterior teeth: Second premolar or first molar extraction preferred to facilitate mandibular closing rotation.
• Minimize posterior tooth extrusion during protraction to enhance rotation.
• Treat after peak pubertal growth spurt – less natural extrusion tendency — greater chance of controlled molar protraction and closing rotation.

5. Pearls for exams & case presentations

When presenting a case, include: vertical pattern, extent of AOB, growth indicators (hand–wrist/CS stage), extraction rationale, and how you’ll control vertical molar movement.

Don’t equate “extraction = guaranteed closing rotation.” The pattern of tooth movement (extrusion vs. translation) and growth stage are decisive. 

Download the paper:

Spotify Episode Link: https://creators.spotify.com/pod/profile/dr-anisha-valli/episodes/Vertical-changes-following-orthodontic-extraction-treatment-in-skeletal-open-bite-subjects-e36qgc5