Springs are a part of the active components of removable orthodontic appliances
used to bring about tooth movement

• Those parts which deliver forces to the teeth and/or skeletal structures to
  bring about changes in position.
• To bring about tooth movement, always use light and continuous forces
• Heavy forces damage the periodontium, bring about root resorption etc

Removable appliance has 3 components

Spring is a part of active component

Components of a spring.

Classification of springs

(1) Based on the presence or absence of helix they can be classified as

• Simple –without helix
• Compound –with helix

(2) Based on the presence of loop or helix they can be classified as

• Helical springs – have a helix
• Looped springs – have a loop

(3) Based on the nature of stability of the springs they can be classified as:

• Self –supported spring = made of thicker gauge wire ,can support themselves
• Supported springs = made of thinner gauge wire and thus lack adequate stability, springs are encased in metallic tube to give adequate support .

Ideal requisites of a spring :-

• Simple to fabricate.
• Easily adjustable.
• Should fit into the avilable space with out discomfort to the patient.
• Easy to clean.
• Should apply force of required magnitude and direction.
• Should not slip or dislodge when placed over a sloping tooth surface
• It should remain active over a long period of time.

Factor to be considered in designing a spring

• Diameter of wire :- flexibility of the spring to a large extent depends upon
  diameter of wire
• The force (F) delivered by a spring is expressed by the formula F α dr4/l3
• F= force applied by spring D=diameter of wire L= length of wire
• Length of wire :- force can be decreased by increasing the length of wire .
• Thus springs that are longer are more flexible and remains active for long
  duration of time .
• By doubling the length of wire force can be reduced by eight times .
• Patient comfort :- spring should be comfortable to patient in design ,
  shape , size or force generation .
• Direction of tooth movement :- the direction of tooth movement is
  determined by the point of contact between the spring and the tooth .
  Palatally placed spring are used for labial and mesio – distal tooth
  movement .buccally placed spring are used when the tooth is to be moved
  palatally and in a mesio-distal direction .

FEW EXAMPLES OF SPRING ARE…

FINGER SPRING

• It is constructed using 0.5 mm SS wire .
• Parts Helix (2 mm) -Active arm -Retentive arm
• The helix is positioned opposite to the direction of intended tooth
  movement.
• It should also be placed along the long axis of the tooth to be moved and
  perpendicular to the directon of tooth movement
• INDICA TION – Mesio-distal movement of teeth e.g. closure of anterior
  diastemas
• Activation Opening the coil or moving the active arm towards the tooth to
  be moved 2-3 mm of activation

Z-SPRING (DOUBLE CANTILEVER ):

• A useful variation of the finger spring where a second limb is formed
  with a second coil.
• Construction: it consists of 2 helices of small diameter can be made for 1
  or more incisors.
• The spring is positioned perpendicular to the palatal surface of the tooth
  with a long retentive arm.
• The Z-spring needs to be boxed in wax prior to acrylization.
• INDICA TION: to move one or more teeth in the same direction E.g.
  proclining 2 or more upper incisors for the correction of anterior tooth
  crossbites.
• To correct mild rotation if only one helix is activated.
• Activation: By opening both the helices up to 2 mm at a time.

CRANKED SINGLE CANTILEVER SPRING

• It is constructed with 0.5mm wire .
• The spring consist of coil , close to its emergence from base plate .
• The spring is cranked to keep it clear of the other teeth .it is used to move
  teeth labially .

T SPRING

• It is made of 0.5 mm wire .
• The spring consist of t shaped arm whose arm are embedded in acrylic.
• It is used for buccal movement of premolar and some canine .
• It is activated by pulling the free end of the spring toward the intended
  direction of tooth movement.

COFFIN SPRING

• It is made of 1.2mm wire .
• It consist of a u or omega shaped wire placed in the midpalatal region
  with retentive arm incorporated in base plates .
• It is retended by adams clasp in molar. It is used in slow dentoalveolar
  arch expansion in patient with upper arch constriction or in unilateral
  crossbite.