Canine retractors are springs that are used to move canine in a distal direction.
🔹ETIOLOGY:
- slightly abnormal path of eruption
- Local tooth displacements as in class 1 malocclusion
- Buccal displacement is more common in crowded arch
- Palatal displacement is more common in uncrowded arch & is associated with small or abnormal root formation of 2’s.
🔹CLASSIFICATION:
1. Based on location
- Buccal (Buccally placed)
- Palatal (Palatally placed)
2. Based on presence of helix or loop
- Canine retractors with helix
- Canine retractors with loop
3. Based on mode of action
- Pull type
- Push type
▪️BUCCAL CANINE RETRACTOR:
INDICATION: Is used where a buccally placed canine has to be moved palatally as well as distally.
TYPES:
• Self supporting or unsupported
• Supported
▪️SELF SUPPORTED BUCCAL CANINE RETRACTOR:
DESIGN & CONSTRUCTION
- 0.7mm wire used
- Coil lies just distal to the long axis of the tooth
- Mesial arm-active arm, should be away from the tissue surface & should run parallel to the long axis of the canine
- At about the middle third of canine a right angled bend is given to the active arm & is adapted on the mesial side of the canine.
- Distal arm-retentive arm, adapted to the mesial aspect of 2 PM
ACTIVATION
👉🏻The spring should be activated by only 1mm. Only spring which is activated by closing the coil
👉🏻Distal activation- It is effected at the coil by bending the anterior limb over the round beak of a pair of spring forming pliers
👉🏻Palatal activation- It is undertaken in the anterior limb after it emerges from the coil
DISADVANTAGES
- More flexible vertically than it is mesiodistally
- Often stiff
- Not indicated in lower arch
▪️SUPPORTED BUCCAL CANINE RETRACTOR:
DESIGN
- Identical in design to unsupported but made from 0.5mm wire supported in tubing
- More than twice as flexible as the standard retractor
- Tubing imparts excellent vertical stability
ACTIVATION
- Activation by 2mm
- Adjustment made as described for self supporting BCR
- More important not to bend the wire where it emerges from the tubing otherwise it may # at this site of stress concentration
▪️AN APPLIANCE TO RETRACT BUCCAL CANINE
Indication
- Class 1 –crowding, upper canines are usually buccally placed
- Class 2- to retract canine to provide space for overjet reduction
- Active component
- Supported buccal canine retractor
- 0.5mm Sheathed in tubing.
- Retention
- adams clasp on 6|6.
- Southend clasp on 1|1.
- Baseplate
- Normal full coverage
- Anchorage
- Spring pressure must be kept light
▪️SOLDERED AUXILIARY SPRINGS TO MOVE A CANINE PALATALLY
• It is possible to solder a spring{0.7mm wire} to the bridge of the adams clasp on a first molar.
• The spring can be used to tuck an outstanding canine
Advantages
- Spring does not cross embrasure & does not compete with other wirework
- Added easily to an existing appliance
Disadvantages
- When the clasp is adjusted the spring position is also affected.
- Difficult to add a spring to a clasp that is already carrying a soldered tube for facebow
▪️REVERSE LOOP BUCCAL RETRACTOR:
INDICATION
- When the canine is placed in the line of the arch & has to be just distalized
- Favored in shallow sulcus as in lower arch
DESIGN
- 0.5mm ss wire used
- The coil is placed as high as possible in the sulcus, but short of the final depth in relation to the space to which the canine has to be moved
- Mesial arm-retentive arm, lies mesial to 2 PM
- Distal arm-active arm. place at right angled bend to the active arm at about the cervical margin of the teeth & adapt it on the mesial side of the canine
ACTIVATION
- Should be activated by not more than 1mm
- Cut off 1mm of wire from the free end & re-forming it to engage the mesial surface of the tooth
- Alternatively it can be activated by opening the loop by 1mm, it is better not to adjust at the loop in lower arch because this moves the active end of the spring occlusally so that secondary adjustment is required
DRAWBACKS
• It is stiff in the horizontal plane yet very unstable vertically
▪️An appliance to retract lower canine
Indication
Anterior crowding
Active component
Reverse loop buccal retractor
Retention
Adams clasp on 6|6
Baseplate
A lingual bar rather than acrylic in the incisor region
Anchorage
Clasped teeth
Teeth and alveolar process contacted by the appliance
▪️U loop canine retractor
INDICATIONS
- Distal movement of canines
- Where functional depth of sulcus is less
DESIGN
- 0.7mm ss wire used
- A U-loop approximately equal to the width of premolar is made
- Mesial arm-active arm. At about the cervical margin of canine,a right angled bend is placed on the active arm to engage the mesial side of the canine
- Distal arm-retentive arm, is adapted mesial to the 2 PM
ACTIVATION – Close the loops by 1mm or free end is cut by 1mm & it is readapted on to the mesial side
DRAWBACKS – Requires frequent adjustments
▪️AN APPLIANCE TO MOVE A CANINE OCCLUSALLY
Indication – Partially erupted canine
Active component – U loop canine retractor, engages a hook bonded to the buccal surface of the canine
Retention – Adams clasp on 6|6
Baseplate – As much palatal coverage as the canine position permits to offer max. resistance to the occlusally directed force
Anchorage – Acrylic in the palate
▪️Buccal acrylic appliance to retract lower canine
Indication – To overcome the dual problems of limited space for tongue & poor retention provided by adams clasp
Active component – Buccal canine spring 0.7mm
Retention – Lingually placed jacksons clasp on the first molar [to overcome the problem of limited undercut on the buccal aspect of lower molars, appliances have been described with clasping on the lingual aspect of molars BELL 1983]
Baseplate – 2 segments of acrylic 1-2mm from the buccal mucosa. These are connected in the midline by a heavy ss bar, {2mm x 1mm}oval in cross section lying close to buccal mucosa below the lower incisors
Anchorage – First molar, with minimal anchorage effect from acrylic
▪️PALATAL CANINE RETRACTOR:
INDICATIONS – In cases where canine is placed palatally & requires distal & buccal movement
DESIGN
- 0.5mm ss wire used
- coil is placed along the long axis of the canine
- Distal arm-active arm, placed mesial to canine
- Mesial arm-retentive arm, is bent at rt angle & extends up to mesial aspect of first molar where a retentive tag is placed
ACTIVATION – By opening the coil by 2-3mm where the active arm emerges out of the coil
▪️CONCLUSION:
• For canine retractors whether buccal or palatal to be successful, it is important for the canines to be mesially angulated prior to treatment
• If the canine is normal & distally angulated prior to treatment, a removable canine retractor will cause an unsightly distal angulation of the canine at the completion of retraction which in turn will take a long time to correct with fixed appliance
• For this reason, use of removable appliance for canine retraction is declining as fixed appliance have greater control over tooth movement
References:
- Textbook of Orthodontics The Art and Science 6th Edition By Bhalajhi; Internet
- Image Source: Google
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