The exact meaning depends on the specialty:

1. Orthodontics (most common use)

• Clear aligners are removable dental devices used to straighten teeth.
• Popular systems include Invisalign.
• They gradually move teeth into proper alignment using a series of custom-made trays.
• Often preferred over braces due to aesthetics and comfort.

2. Orthopedic Surgery

• Aligners can refer to external or internal devices that help align bones:
  
  • External fixators (frames outside the body holding bones in place)
  • Intramedullary nails or rods used to maintain bone alignment
• Used in fracture repair or limb deformity correction.

3. Maxillofacial Surgery

• Surgical aligners or splints are used to guide jaw positioning during procedures like orthognathic surgery.
• They ensure proper bite (occlusion) after repositioning the jaw.

4. Spinal Surgery

• Alignment tools (not always called “aligners” formally) help correct spinal curvature or positioning, especially in scoliosis treatment.