Hawley Retainer

The Hawley Retainer is the most classic removable orthodontic retainer, invented by Dr. Charles Hawley in 1919. It consists of an acrylic baseplate that fits snugly against the palate (or lingual surface for lower), combined with a labial bow wire across the anterior teeth and Adams clasps on the first molars. It is used to maintain tooth positions after orthodontic treatment and can be activated to close minor anterior spacing.

• Acrylic Baseplate — Heat-cured PMMA, 1.5–2.0mm thickness, full palatal coverage (upper) or lingual horseshoe (lower) • Labial Bow — 0.7mm stainless steel wire, running across the middle third of the 6 anterior teeth • Adams Clasps — 0.8mm stainless steel wire on first molars, arrowheads engaging mesial and distal undercuts • U-Loops — 3–4mm vertical loops at the canine area for adjustability • Optional: Midline expansion screw (Dentaurum 602-810) for arch width maintenance

The Hawley Retainer works by passively holding teeth in their corrected positions through a combination of acrylic baseplate contact and wire retention. The labial bow prevents anterior teeth from shifting labially, while the Adams clasps anchor the appliance to the posterior teeth. Unlike active appliances, the Hawley is primarily passive — but the labial bow can be activated by compressing the U-loops to close minor anterior spacing (up to 1–2mm).

1. Receive intraoral scan (STL) from iTero, 3Shape TRIOS, Medit, or Carestream 2. Review and refine the digital model — repair mesh errors, trim excess data 3. 3D-print the working model in high-resolution resin (50μm layer) 4. Hand-bend 0.7mm labial bow and 0.8mm Adams clasps on the printed model 5. Wax up the acrylic baseplate area 6. Flask, pack with heat-cured PMMA, and process 7. Deflask, trim, and polish to a high gloss 8. QC: Verify clasp retention, baseplate fit, and labial bow position against the prescription

• Wire: ASTM F899 stainless steel — 0.7mm (labial bow), 0.8mm (Adams clasps) • Acrylic: ISO 20795-1 heat-cured PMMA, clear or pink • Baseplate thickness: 1.5–2.0mm (palatal), uniform, no voids • Clasp engagement: Arrowheads must engage mesial and distal undercuts with passive fit • Labial bow: Positioned at middle third of anterior clinical crowns • Polish: High-gloss finish, no sharp edges • QC: Visual inspection under magnification, fit check on original model, passive fit verification