Indications:

• Skeletal maxillary transverse deficiency requiring orthopedic expansion.

• Posterior crossbite (skeletal origin).

• Moderate crowding relief by increasing arch perimeter.

• Patients where control of both transverse + anteroposterior/vertical dimensions is desirable.

Contraindications:

• Fully fused midpalatal suture (late adults, unless SARME is planned).

• Poor periodontal support/poor oral hygiene.

• Severe vertical growers (risk of bite opening).

• Palatal pathology or insufficient inter-radicular space for screw arms.

Corrects:

• Skeletal transverse constriction by midpalatal suture opening.

• Posterior dental crossbite.

• Can produce minor distalization or anterior retraction depending on screw orientation.

• Allows 3-dimensional expansion (transverse, sagittal, vertical control).

Design:

• Based on conventional Hyrax jackscrew but with 3D modification:

  • Screw has additional arms extending anteriorly and posteriorly.

  • Permits activation in multiple vectors → transverse (lateral expansion), sagittal (distalization of molars), and some vertical control.

• Banded to maxillary first molars ± premolars.

• Activation ~0.25 mm per turn, usually 2 turns/day.

Philosophy:

• Extends the concept of RME beyond simple transverse expansion.

• By modifying screw design and arm orientation, appliance produces 3D orthopedic and dental changes.

• Forces are heavy and intermittent → mainly skeletal separation, but with dental effects.

Modifications:

• Bonded 3D Hyrax: with acrylic covering posterior teeth for bite opening and vertical control.

• Facemask + Hyrax 3D: for simultaneous expansion + protraction in Class III.

• Hybrid 3D Hyrax: supported with miniscrews for skeletal anchorage (to reduce dental tipping).

• Asymmetric activation: to correct unilateral crossbite.

Advantages:

·         3D skeletal expansion – provides simultaneous transverse, sagittal, and vertical control of the maxilla.

·         Rigid jackscrew system – delivers high orthopedic forces for predictable midpalatal suture separation.

·         Banded design – stable anchorage through molars/premolars with soldered framework.

·         Versatile use – effective in correcting posterior crossbite, narrow maxilla, and transverse discrepancies.

·         Improves airway – widens nasal cavity and can reduce airway resistance.

·         Can be combined with facemask or fixed appliances – for sagittal corrections in Class III cases.

·         Durable stainless-steel construction – provides long-term stability during activation phase.

Customizable – can be designed for differential expansion depending on clinical need.