Tricks of the Trade: How to disimpact an ectopic first permanent molar

The prevalence of ectopic eruption of first permanent molars (FPMs) ranges from 0.75% to 6% in different populations, with some studies reporting a higher occurrence of impaction in the maxilla compared to the mandible.^1–5 Often, the clinical presentation is of an upper FPM trapped in the convexity below the cemento-enamel junction of the primary second molar, sometimes causing resorption of the distal root of the primary tooth. In most cases, this results in a self-fulfilling preponderance of impaction because the FPM is trapped under the non-resorbable enamel shelf of the primary molar. The milder impactions may self-correct, but it has been reported that self-correction reduces after age 7 years.³ Clinicians may be tempted to extract the primary second molar, but this leads to the undesirable consequence of mesial drift of the FPM, and subsequent problems of severe crowding and the practical difficulties of distalizing the FPM (Figure 1).