Elastomeric and Auxiliary Appliances
What this domain tests
How elastomeric ligatures, chain, separators, and intermaxillary elastics behave over time; how auxiliary appliances are selected; and what patients must be told for them to work.
Elastomerics
Ligatures and chain are polyurethane, latex or non-latex. Force decays fastest in the first 24 hours, then more slowly, so elastomerics are replaced at each 4–6 week visit. A figure-8 tie delivers more force and better rotation control than a single tie. Power chain closes space; open chain maintains it. Separators are placed about one week before banding, two per contact, and are temporary - warn patients they can swallow one.
Intermaxillary elastics
- Common configurations: Class II (upper canine to lower molar), Class III, vertical, cross, box, triangle.
- Wear 22–24 hours a day, removed only for eating and brushing; replace them one to two times daily because force decays.
- Typical force ranges are 2–8 ounces; the orthodontist selects size and vector.
- Screen for latex allergy before handing a latex bag; keep non-latex stock.
Fixed and removable auxiliaries
- Open coil spring opens space; closed coil closes or maintains space; NiTi coils deliver light continuous force.
- Crimpable hooks and stops reposition force vectors without changing wires.
- Headgear (cervical or high-pull), facemask, transpalatal arch, Nance, quad helix, lingual arch, rapid palatal expander (about 0.25 mm per turn), and temporary anchorage devices.
- Retention: Hawley, vacuum-formed, and bonded lingual 3–3 retainers; wear schedules change over time and relapse risk never disappears.
Worked example
A 12-year-old says his Class II elastics "don't work." He wears them overnight and at school but removes them for sports and meals, roughly four hours a day out. Reasoning: elastics need 22–24 hours to produce sustained force; intermittent wear lets the teeth relapse between sessions. Check that the bands are the correct size, that attachments are present, and document the wear discussion. The fix is a clear hours-based instruction and a compliance check at the next visit, not a stronger elastic.
Traps that cost marks
Telling a patient to wear elastics "as much as possible" instead of giving hours; assuming a chain is still active at week eight; confusing open and closed coil; handing latex without asking about allergy; and forgetting that separators, elastics, and ligatures are all swallowable.