Ectopic Eruption of Maxillary First Molars
Ectopic eruption of the maxillary first molars involves a mesial eruption path that may cause impaction against the second primary molar. The condition can be reversible or irreversible. Diagnosis is clinical and via X-ray. Treatment may include separation, grinding, or extraction.
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This article is based on an original article in Swedish which can be found here
BACKGROUND
Ectopic eruption of the maxillary first permanent molars (6s) means that these erupt with a more mesial eruption direction than normally erupting first permanent molars, and become locked distally on the second primary molars where atypical resorption occurs. This prevents the 6s from achieving full eruption with a normal inclination. Two types of ectopic eruption can be distinguished; the reversible type where the 6s spontaneously free themselves from the eruption lacunae and achieve full eruption, and the irreversible type where the 6s remain locked in place until the primary molars exfoliate or some type of treatment needs to be performed (see Figure 1)(1-6).
Prevalence
The occurrence of ectopic eruption of the maxillary 6s varies in different studies between 2 and 6%. In Scandinavian materials, the prevalence is approximately 4.5%, of which about 1.8% is of the irreversible type. In a sibling group of children with ectopic eruption, however, the prevalence is significantly higher, around 20% (7).
Etiologic factors
The most common etiologic factor of ectopic eruption of the maxillary 6s is believed to be that the buds develop with a more mesially directed eruption. There are also studies suggesting that these molars are somewhat wider mesiodistally than an average first molar in the maxilla (8). The first studies published regarding this eruption disturbance indicated that the cause was due to small maxillas.
