Scanning electron microscopic observations on the eruption of primary teeth in the opossum.

Just prior to the emergence of the tooth into the oral cavity, a small circular crater forms in the gingival epithelium immediately above the crown. The craters appear to expand in diameter during eruption to accommodate the emerging crown of the tooth. The observations support the concept that the crown of the tooth does not actively push through and rupture the gingival epithelium, but rather that the epithelium degenerates and then the tip of the crown emerges into the formed defect.