Miniscrew-Assisted Rapid Palatal Expansion (MARPE) allows skeletal expansion of the maxilla in adults and can reduce the need for Surgically Assisted Rapid Palatal Expansion (SARPE).

However, expansion forces may spread to surrounding craniofacial structures.

Finite element studies show forces of up to100 N can reach:

• Zygomatic arch

• Infraorbital rim

• Pterygoid processes

• Sphenoid bone

These forces may occasionally cause unwanted craniofacial fractures or sutural disjunctions(diastasis)

Diastasis vs fracture

Diastasis

• Abnormal separation of a suture or synchondrosis

• Occurs without cortical bone disruption

• Represents a physiological or mechanically induced separation when forces are controlled.

Fracture

• Discontinuity of cortical and trabecular bone

• Often accompanied by:

  • Irregular margins

  • Displacement of bone segments

  • Possible soft tissue compromise.

In palatal expansion:

• Diastasis → intended orthopedic outcome

• Fracture → unintended complication due to excessive or misdirected force.

2. Study Aim

The study aimed to report clinical cases of craniofacial complications occurring after MARPE or MASPE and analyze the possible biomechanical causes.

3. Materials and Methods

• Retrospective clinical case series

• Cases collected from clinicians with >10 years of experience in skeletal expansion.

• Treatments included:

  MARPE

  • Rapid activation

  • 2 turns per day

  MASPE

  • Force-Controlled Polycyclic Protocol (FCPC)

  • Duration 3–6 months

  • Torque wrench forces maintained below 500 cN

• Expanders were supported by 4 palatal mini-implants.

4. Patient Sample

• 12 patients

• Mean age: 30.2 ± 9.7 years

• Sex distribution:

  • 10 females

  • 2 males

CBCT imaging was available for 7 cases.

5. Observed Complications

Most common finding

Asymmetric fractures of the frontonasal process of the maxilla

• Occurred in 6 patients

• Defined as >3 mm transverse asymmetry between hemimaxillae.

Other complications

• 1 zygomatic bone fracture

• 2 orbital diastases

• 1 zygomaticomaxillary diastasis

• 1 parasagittal fracture of the palatine bone (MASPE case)

  These complications were mainly reported in patients who underwent MARPE using rapid activation protocols. Only one minor complication was noted in a MASPE case, where the patient adhered to the recommended slow activation schedule.

6. Clinical Symptoms

Patients showed varying symptoms, including:

• Facial asymmetry

• Nasal asymmetry

• Orbital dystopia

• Diplopia

• Epiphora

• Infraorbital nerve numbness

No patient required emergency surgical treatment.

recommendation for clinicians facing such a situation is to progressively deactivate the appliance in order to reverse the cranial fracture or diastasis and to allow a prudent healing period of a few weeks, since in many cases the symptoms of diplopia, infraorbital nerve hypoesthesia, and epiphora tend to be reversible and without long-term consequences

7. Biomechanical Explanation

During MARPE expansion:

• Stress spreads through circummaxillary sutures and craniofacial buttresses.

• High resistance areas include:

  • Zygomatic arch

  • Pterygopalatine region.

According to Isaacson, as patient age increases, greater expansion forces are required to achieve midpalatal suture opening

8. Timing of Complications

Most complications occurred around the third week of expansion.

Slowing the activation rate and increasing the interval between turns of skeletal expanders over a longer period may help reduce cranial stress

9. Force Control Recommendations

The authors recommend:

• Limiting initial expansion torque to ≤500 cN

• Corresponding force: ~100–130 N

If the midpalatal suture does not open within 4 weeks, clinicians should consider SARPE.

Other Methods to avoid complications:

• Adopt slower activation protocols after the mid-palatal split

• ultra-slow MASPE protocols with rest cycles

• expanders designed for better force distribution – Newer devices, such as the ATOZ expander, aim to distribute expansion forces more evenly, which may contribute to safer treatment outcomes.

10. Alternative Expansion Approaches

MASPE

Uses controlled activation cycles and may reduce stress transmission.

SARPE

Surgically separates maxillary buttresses, allowing maxillary expansion without transmitting excessive forces to the cranial base.

Key Clinical Message

Unwanted craniofacial fractures during MARPE/MASPE are rare but possible.

Risk reduction strategies include:

• Monitoring expansion forces

• Using force-controlled activation protocols

• Careful CBCT assessment

• Considering MASPE or SARPE when resistance is high.

References:

Walter A, Winsauer H, Crespo E, Arcos I, Valls-Ontañón A, Puigdollers-Perez A, Hernández-Alfaro F. Unwanted creaniofacial fractures in MARPE/MASPE patients: a hidden risk? Prog Orthod. 2025 Dec 5;26(1):51. doi: 10.1186/s40510-025-00592-0. PMID: 41348293; PMCID: PMC12680809.