| Field | Value |
|---|---|
| ID | OA-0327 |
| Type | expander |
| Category | expander |
| Fixed/removable | removable (standard); fixed variant available |
| Primary function | sagittal arch development; anterior/posterior crowding relief |
| Malocclusion target | crowding; arch length deficiency |
| Inventor | various (mid-20th century European tradition) |
| First year | 1950s |
| Period | historical / current |
| Status | current |
| Uses TADs | no |
A sagittal appliance is a removable plate with one or more expansion screws oriented in the sagittal (anteroposterior) plane rather than the transverse plane. The screw activation moves the anterior or posterior segments forward or backward relative to the anchor section, effectively recovering arch length lost to early tooth loss, crowding, or mild collapse. Two- and three-way sagittal variants allow simultaneous anterior and posterior arch development. It is common in European-tradition orthodontics and pedodontics for phase I crowding management.
When the patient or parent activates the screw (typically ¼ turn every 3–5 days), the two halves of the acrylic baseplate are pushed apart along the sagittal axis. This tips the anterior teeth forward (increasing overjet) or moves the posterior segment back (creating space), depending on screw placement and design. The acrylic occlusal coverage maximizes posterior anchorage while the mobile section carries the teeth to be moved. The effect is purely dentoalveolar — sagittal plate appliances do not produce skeletal changes.
Mild anterior crowding where a small amount of arch length can be recovered by anterior tooth proclination; mild arch collapse following premature tooth loss; creating space for eruption of a crowded incisor; phase I treatment in mixed dentition to avoid premolar extraction in borderline cases; combination with transverse expansion (using a separate or combined screw) in multi-plane arch development. Two- or three-way versions are used when both anterior and posterior development is needed simultaneously.
Patient compliance is essential — the appliance must be worn 20–22 hours/day and the screw must be activated as instructed. Proclines the incisors — not appropriate if incisors are already proclined. Cannot address severe crowding or skeletal problems. Produces tooth tipping, not bodily movement. Fixed sagittal version has no compliance issue but requires good band fit and is harder to adjust.
occlusal surfaces
anteroposteriorly
premolars/canines
anterior and posterior independently
Screw placement must align precisely with the desired plane of movement — a screw even slightly off-axis delivers unintended tipping or rotation. The acrylic must provide maximum posterior coverage (occlusal rests on molars) to anchor the fixed segment while the mobile section moves. Adams clasp fit on the molars is the primary retention — undersized clasps lead to appliance dislodgement. Polish all acrylic surfaces smooth. For the fixed sagittal variant, the appliance is constructed on molar bands and cannot be removed by the patient. The removable version is more common for mixed-dentition management.
common.
simultaneously.
anterior/posterior/transverse.
.
Ortho](https://fivestarortho.com/appliances/sagittals/)
DynaFlex](https://www.dynaflex.com/orthodontic-laboratory/removable-appliances/schwarz-sagittal/)
Lab](https://www.qcortho.com/expansion-and-arch-development.html)
business notes.