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.

---

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