Double cantilever spring OR Z-spring

 Z-Spring

Double cantilever/Z-spring can be used for the labial movement of palatally locked incisors and also for correcting minor rotations of these teeth.

Parts of Z-Spring

a. Square loop

b. Two helices

c. Retentive arm

d. Retentive tag

Helices of Z-spring

There are two helices of small internal diameter.

Squarsh loop: Active arm with squarsh loop is incorporated at the free end of active arm and it helps in preventing soft tissue damage.

Retentive arm: It has a long retentive arm of about 10 to 12 mm length, which gets embedded in acrylic base material.

Retentive tag: Retentive tag of Z-spring is perpendicular to the retentive arm and is of 2 to 3 mm in length.

Fabrication

 Stainless steel wire of 0.5 mm or 23 gauge isn used for the fabrication of Z-spring.

 Pliers used: Universal pliers can be used for the fabrication of Z-spring.

 Z-spring can be designed to more one or two incisor in a labial direction over equal distances.

 The spring is constructed such that it is perpendicular to the palatal surface of the teeth to be moved.

 Z-spring is a supported spring and needs boxing in the wax prior to acrylization. However, the helices are kept free from acrylic so that they can be activated.

Activation of Z-Spring

 For labial movement of incisors, the Z-spring is activated by simultaneously opening both helices by 2 to 3 mm.

 For correction of minor rotations, activation is done by opening only upper helix by 2 to 3 mm.

Uses

Z-spring is used for:

a. Labial movement of one or two incisors. It is often used for correction of anterior crossbite occurring due to palatally locked upper incisors.

b. It can also be used for the correction of mild rotation of incisors.