Impacted Canine

An impacted canine is a canine that fails to erupt by the expected age and remains in the jaw, partly or completely covered by bone or soft tissue. The maxillary canine is the most commonly impacted tooth after the third molar, with a prevalence of about 1 to 3%.

About 85% of maxillary canine impactions are palatal in white populations, and the proportion is lower in Asian populations, with more buccal impactions. Mandibular canine impaction is rare. Women are affected more than men, about 2 to 1.

Pathophysiology. The canine develops high in the maxilla and has a long path of eruption, directed by the root of the lateral incisor. Absence, a small or peg shaped lateral incisor, crowding, a retained primary canine, cysts and genetic factors disrupt the path.

Complications are resorption of the roots of adjacent incisors (about 12 to 38% in CT studies), cyst formation, displacement of the neighbouring teeth, loss of space and infection.

Usually no symptoms. Findings: delayed exfoliation of the primary canine or persistence beyond 14 to 15 years, absence of the canine bulge on palpation of the buccal sulcus by 10 to 11 years, a palatal bulge, a lateral incisor that is tilted or has a distal flare, a diastema, and a missing permanent canine. Pain or swelling suggests cyst formation or infection.

Ask about a family history, and check the lateral incisors and neighbouring teeth.

Rapid swelling, pain, mobile incisors from root resorption, or a suspected cyst or tumour need prompt assessment.

• Clinical palpation of the canine bulge from age 9 to 10 years, with an assessment of the eruption path.
• Panoramic radiograph, with periapical views taken with different horizontal angles (parallax: the object that moves in the same direction as the tube is palatal), and an occlusal view.
• Cone beam CT for the exact position, angulation, relation to incisors, resorption and the presence of a cyst. This is the preferred imaging when root resorption is suspected.
• Features that predict impaction: angle of the canine to the midline over 31 degrees, overlap of the lateral incisor root, and the canine crown over the lateral incisor root.
• Assessment of the lateral incisors for resorption.

Differential diagnosis.

• Delayed eruption without impaction
• Congenital absence of the canine
• Transposition of the canine and first premolar
• Dentigerous cyst around the crown
• Odontoma obstructing eruption
• Ankylosed canine
• Root resorption of the incisors from other causes

• Interceptive: when palpation is absent and the canine is mesially angled in children aged 10 to 13 years, extract the primary canine, which improves the position in about 60 to 80% when the canine is not too far displaced. Review at 6 to 12 months.
• Surgical exposure and orthodontic traction: expose the impacted canine under local or general anaesthesia (open exposure with a window, or closed exposure with bonding of an attachment and traction), then bring it into the arch with orthodontic forces. This is the treatment of choice in a young patient with a favourable position.
• Extraction of the impacted canine with orthodontic space closure, a prosthetic replacement or an implant, when the position is poor, the tooth is ankylosed, resorption of adjacent teeth is severe, or the patient declines treatment.
• Autotransplantation in selected cases.
• Observation with regular radiographs in older patients with no symptoms and no pathology.
• Cysts: enucleation with removal or exposure of the tooth.
• Antibiotics: single dose of cefazolin 2 g intravenously (3 g if over 120 kg) at induction for surgery in selected patients, or none. Clindamycin 600 mg intravenously in penicillin allergy.
• Analgesia: paracetamol 1 g every 6 hours (maximum 4 g daily) with ibuprofen 400 mg every 8 hours with food. Children use paracetamol 15 mg/kg every 4 to 6 hours (maximum 75 mg/kg daily) and ibuprofen 5 to 10 mg/kg every 6 to 8 hours.

Special groups. Children with resorption of the lateral incisor roots need early treatment and orthodontic planning. Adults over 30 have a higher rate of ankylosis and failure of traction.

Monitoring. Review at 6 to 12 months after interceptive extraction, every 3 months during traction, and annually for retained impacted teeth. Radiographs for resorption and cysts.

Referral and escalation. Refer to orthodontics and oral and maxillofacial surgery by age 10 to 11 years when the canine bulge is absent. Urgent referral for cyst, infection or marked resorption of adjacent teeth.