Schwarz Appliance

The Schwarz Appliance is a removable split acrylic baseplate with a midline expansion screw. Named after the German orthodontist Schwarz, it is the most commonly prescribed slow-expansion appliance for maxillary transverse deficiency.

• Split Acrylic Baseplate — Left and right halves with midline gap • Midline Expansion Screw — Dentaurum 602-810, 0.25mm per quarter-turn • Adams Clasps — 0.8mm SS wire on first molars • Labial Bow — 0.7mm SS wire (optional) • Posterior Retention — Acrylic covering posterior palate and alveolar ridges

The patient or parent activates the screw with a key 2-3 times per week (0.5-0.75mm/week). Each quarter-turn (90°) expands the split baseplate 0.25mm, delivering slow, controlled transverse forces to the posterior teeth and alveolar processes.

1. Receive intraoral scans 2. 3D-print working model 3. Position expansion screw at the deepest point of the palatal vault 4. Wax left and right baseplates separately — ensure screw is free to rotate 5. Bend Adams clasps (0.8mm) and labial bow (0.7mm) 6. Flask and process with heat-cured PMMA 7. Separate left and right halves along the midline 8. Verify screw rotates freely — 4 clicks per full turn 9. QC: Screw function, clasp retention, midline alignment

• Screw: Dentaurum 602-810/820, stainless steel, 0.25mm/quarter-turn • Acrylic: Heat-cured PMMA (ISO 20795-1), minimum 2.0mm thickness • Clasps: 0.8mm ASTM F899 SS; Labial Bow: 0.7mm • Maximum expansion: 6-8mm before screw replacement needed • Activation: 0.5-0.75mm per week • QC: Screw rotation test (must turn freely), clasp engagement, midline alignment