Orthodontics · patient case question
What is Patient B's anomaly, and what is the usual management?
Patient case: Four developmental anomalies
Patient: Four patients
Chief Complaint: A: “One back tooth bleeds when I floss.” B: referred for orthodontic assessment. C: mother reports the child's teeth on one side “look different”. D: referred for root canal treatment.
Background: A, 45-year-old male: excellent plaque control, no periodontal disease elsewhere. B, 13-year-old female: no medical history. C, 8-year-old male: unremarkable medical and family history. D, 36-year-old female of East Asian ancestry.
Findings: A: an ISOLATED 8 mm furcation pocket on a molar in an otherwise healthy mouth, with a well-defined radiopaque nodule at the furcation. B: the maxillary canine and first premolar have exchanged positions in the arch. C: several ADJACENT teeth in one quadrant with markedly thin enamel and dentine, disproportionately large pulp chambers and poor contrast, with an abrupt cut-off at the midline. D: mandibular first molar in which the root outline appears unusually wide and the periodontal ligament outlines do not resolve into two roots.
Show answer and explanation
Correct answer: B. Transposition — usually accept the position and align the teeth as they lie, reshaping to mimic normal morphology
- A. TRANSMIGRATION is a genuinely different phenomenon and worth knowing separately: an unerupted tooth, almost always the MANDIBULAR CANINE, migrates across the MIDLINE within bone.
- B. CORRECT. TRANSPOSITION is the positional interchange of two ADJACENT teeth, or the development of a tooth in the position normally occupied by a non-adjacent tooth. The maxillary CANINE and FIRST PREMOLAR is by far the commonest pair, followed by the maxillary canine and lateral incisor, and it occurs more often in the maxilla. It is associated with other anomalies — hypodontia, peg-shaped lateral incisors and retained primary teeth — so finding one should prompt a look for the others. Management is usually to ACCEPT the transposition and align the teeth in their transposed positions, reshaping them to mimic the correct morphology, because attempting to move two fully formed roots past each other risks root resorption and bone loss.
- C. Migration is drifting from the normal position, typically following tooth loss or periodontal breakdown. It does not involve two teeth exchanging places. And correcting a complete transposition orthodontically is precisely what is usually NOT attempted.
- D. Ectopic eruption describes a tooth erupting along an abnormal path — most commonly a maxillary first molar resorbing the distal of the second primary molar. Extracting a sound premolar is not a first-line answer to anything here.
Note: Correction is only considered where the transposition is INCOMPLETE and identified early, while the roots are still developing and can be guided. In a complete transposition with formed roots, accepting and camouflaging is the standard approach — reshape the canine cusp tip and recontour the premolar, or restore both with composite or veneers.