Palatal maxillary canine impaction, peg-shaped lateral incisor anomaly, and deciduous canine retention

Case contributed by Francis Deng
Diagnosis almost certain


Evaluation for orthodontic treatment

Patient Data

Age: 18 years
Gender: Female

There is a complement of 34 teeth with the following abnormalities:

  • bilateral impacted maxillary canines
  • bilateral peg-shaped maxillary lateral incisors
  • bilateral overretained maxillary deciduous canines
  • maxillary midline diastema
  • bilateral impacted maxillary and mandibular wisdom teeth

The bony impacted permanent maxillary canines are palatal to the rest of the dental arch. Other findings from the orthopantomogram are confirmed bilaterally:

  • peg-shaped maxillary lateral incisors
  • over-retained deciduous maxillary canines
  • maxillary midline diastema, measuring 2 mm
  • impacted maxillary wisdom teeth
  • impacted mandibular wisdom teeth, the root apices of which marginate the buccal aspects of the inferior alveolar nerve canals

Case Discussion

The most common tooth impactions involve the 3rd molars (wisdom teeth) and then the maxillary canines. Palatal maxillary canine impaction in particular is frequently associated with anomalous (small or peg-shaped) maxillary lateral incisors, which are the most common tooth involved in microdontia. The maxillary primary canines are the second most common over-retained primary teeth (after the maxillary second molars).

The guidance theory of palatally displaced maxillary canines posits that when the permanent lateral incisor develops later than is typical, the developing canine can migrate mesial to it because it lacks the normal guidance of the lateral incisor to erupt against 1. Although the apex of the impacted canine is usually located in the usual mesiodistal location, the crown migrates abnormally towards the midline and along the palatal periosteum. As a consequence, the deciduous canine may be over-retained and the midline maxillary diastema does not close.

As in this case, CT may be obtained to localize the position of impacted teeth in the buccopalatal direction when it is unclear from radiographs and physical exam. CT is also indicated to evaluate the position of mandibular wisdom teeth in relation to the inferior alveolar nerve canals for surgical planning. The disadvantage of CT, particularly in pediatric patients, is the stochastic risks of ionizing radiation exposure. In this case, dose reduction techniques were employed including limited axial coverage (5 cm scan length centered on the maxillary dental arch, head positioned with the beam close to parallel to the hard palate) and low dose output parameters (80 kVp, 20 mAs, 0.5 s rotation time, 0.9 pitch), leading to a dose-length product (DLP) of only 9 mGy*cm, which converts to an effective dose of less than 0.02 mSv.

The radiological appearance in this case should be distinguished from supernumerary teeth based on the appearance and position of each abnormal tooth. Retained deciduous teeth have smaller crowns and roots than supernumerary permanent teeth.

This patient was referred to an oral surgeon for extraction of the wisdom teeth and primary canines, as well as exposure and bonding of the permanent canines, to be followed by orthodontic treatment.

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