A coil of fine wire capable of returning to its original shape when bent. An apron spring is a component of a removable orthodontic appliance used to reduce an overjet. It is a flexible spring (0.35–0.4mm diameter) attached to a high labial bow which is constructed from a stiffer archwire (0.9mm). A Coffin spring [C. R. Coffin (1826–91), American dentist] is an omega-shaped (Ω) spring made of heavy-gauge wire, crossing the palate as part of a removable orthodontic appliance (e.g. the Bimler or the Crozat appliance); it provides the possibility of expansion or constriction of the maxillary dental arch. A finger spring consists of a short piece of wire, usually about 0.5 millimetres in diameter, forming part of an orthodontic appliance which acts as a lever to apply force to a tooth and achieve a tooth tipping movement; it may be placed buccally or palatally. Finger springs can contain helices to increase the effective wire length for added flexibility. A flapper spring is wire bent in the form of a ‘box’ incorporated into a removable appliance to tip an individual tooth or groups of teeth buccally or labially; it has the same action as a Z spring. A rotation spring is used in the treatment of class II and class III jaw malocclusions and may be geometrically shaped as a ‘U’ or an ‘S’, that terminates at one end in a tube for the passage and retention of a tie wire, and at the other end with a curved surface. The entire spring is designed to provide compression between an archwire attached to an orthodontic bracket and a tooth band. A force is created which acts to rotate the tooth about its axis. A T spring is used for the buccal movement of a single molar or premolar tooth; it is activated by pulling the spring away from the acrylic base plate at an angle of 45°. A Z spring ( recurved spring) is wire bent in the form of a ‘Z’, incorporated into a removable appliance used to tip an individual tooth or groups of teeth either buccally or labially.
Types of orthodontic springs