Palatally impacted maxillary canine: imaging decisions and traction planning
A 13-year-2-month-old boy is referred because the upper right canine has not erupted. The retained primary canine (53) is slightly mobile; the upper right lateral incisor (12) is in normal position with no obvious displacement. The panoramic radiograph shows the crown of 13 overlapping the root of 12, with the long axis of 13 at about 40 degrees to the occlusal plane and the crown above the level of the 11 apex. The general dentist has requested a cone-beam CT (CBCT) before any surgery. The remaining permanent dentition is erupted except the third molars; overjet is 3 mm, overbite 25%, and there is 2 mm of lower incisor crowding. The parents want to know whether the canine can be brought into the arch or should be removed, and whether the CBCT is really necessary.
1. What would you specify for the CBCT and what findings would change your treatment plan?
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I would request a small field-of-view, low-dose scan of the maxilla at a voxel size of about 0.2–0.3 mm, reconstructed in axial, coronal and sagittal planes plus curved multiplanar views along the canine. The questions are: is the crown labial or palatal to the incisor roots; what is its angulation and height relative to the alveolar crest; how close is it to the roots of 11 and 12; is the follicle enlarged; is the periodontal ligament space visible around the canine root; is there root resorption of 12; and is the canine transmigrant.
These findings change management. A palatal, high, horizontally angled canine is better managed by closed exposure with a gold chain than by an open window. If the crown is labial and near the crest, open exposure with a bonded attachment may be simpler. Evidence of root resorption of 12, an ankylosed-looking root with loss of PDL space, or a transmigrant canine that cannot be moved into the arch would push me toward extraction and later prosthetic replacement. The CBCT is justified because the panoramic image cannot resolve bucco-palatal position or incisor root damage, and the surgical approach depends on it.
2. Outline the surgical exposure and orthodontic mechanics, including force levels and the sequence.
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Assuming a palatal position with 40 degrees of angulation and no incisor root damage, I would use closed eruption. Under local anaesthesia the surgeon raises a palatal flap, exposes the crown, bonds an attachment with a gold chain, and returns the flap; the chain exits through the flap or a small window. I would then create space for the canine in the arch first, using the available 2 mm of crowding relief and, if needed, distal movement of the buccal segment.
Traction starts with about 50–60 g of light continuous force from the chain to the archwire, directed to move the crown away from the incisor roots and toward the alveolar ridge. The first goal is to move the crown occlusally and buccally out of the bone; alignment follows. Radiographs every 3–4 months check the canine root and the roots of 11 and 12. If the canine is very high or the path is unfavourable, a temporary anchorage device or a cantilever from the archwire can provide a more controlled vector. Do not apply heavy forces; they increase anchorage loss, tipping and root resorption.
3. Six months later the chain is still under tension but the canine has not moved and percussion is dull. How do you reason through this, and what are the options?
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Failure to move despite maintained tension, together with a dull percussion note, raises ankylosis. I would confirm with a periapical or small-field CBCT: continuity of the PDL space, root outline, and whether the attachment is intact and the chain is truly under tension. A debonded attachment or a chain buried in tissue is a common and reversible explanation, so check that first. If the attachment is intact and the PDL is obliterated, I would stop traction.
Options then depend on the patient. If the canine is ankylosed and cannot be moved, extraction with prosthetic replacement after growth (an implant-supported crown or a resin-bonded bridge) is the realistic route; auto-transplantation is possible in selected cases but has a high failure risk and should not be presented as routine. I would also check the roots of 11 and 12 for resorption, and if resorption is progressing I would extract the canine earlier rather than later. The parents should be told that continuing traction on an ankylosed tooth risks damaging the anchor teeth and the alveolar bone.