Eruption sequestrum, a rare dental anomaly, was initially described by Starkey and Shafer [1] in 1963. To date, a comprehensive review of the English literature has documented only 21 reported cases of ES [1,2,3,4,5,6,7,8,9,10,11,12]. Based on our analysis of these cases, ES predominantly occurs unilaterally (66.7%), in the mandible (76.2%), in both the mandible and maxilla (9.5%), on first molars (76.2%), and on second molars (23.8%), exhibiting minimal gender disparity (57.1% male versus 42.9% female) (Table 1).

The pathogenesis of ES remains debated. Starkey and Shafer [1] originally hypothesized that cortical bone fragments trapped during eruption were the primary etiology. However, the clinical manifestations reported by Watkins [2] and Priddy et al. [5] in cases consistent with ES demonstrated that the calcified fragments were predominantly composed of dentin and cementum, rather than free bone tissue. Similarly, Onishi et al. [8] identified the presence of dentin, cementum, and pulp-like components within the hard tissue. The pulp-like connective tissue within the mass was richly vascularized, and the cells embedded in the osteodentin-like components remained active, suggesting that the calcified tissue was in a continuous developmental state. Based on these findings, Onishi et al. [8] proposed, for the first time, that ES might represent a calcifying hamartoma of mesenchymal origin. The histopathological analysis conducted by Roza et al. [12] further supports this perspective, defining ES as a hamartoma with limited developmental potential. Additionally, they noted chronic inflammatory infiltrates in the soft tissue. Integrating these observations with previous literature documenting chronic inflammation in the soft tissue, Roza et al. [12] suggested the term inflamed odontogenic hamartoma to more accurately describe ES. This nomenclature better encapsulates the pathological characteristics and developmental nature of the lesion.

Histologically, ES typically presents as non-viable, dense bone with empty lacunae lacking osteocytes, often accompanied by evidence of necrosis [1, 4, 7, 9,10,11]. Limited histopathological descriptions are available regarding the adjacent soft tissues in ES cases, with most reports indicating the presence of chronic inflammatory infiltrates associated with epithelial structures [4, 8, 9, 12], while a few cases have mentioned odontogenic epithelial proliferation [5, 12]. In the present case, histopathology of the soft tissues revealed features consistent with chronic inflammation, with the additional finding of subepithelial fibrous hyperplasia. Biochemical analyses remain limited, although Maki et al. [9] reported a calcium-to-phosphorus ratio (78.41%:21.59%) exceeding normal bone values, suggesting an active mineralization process rather than inert bone remnants.

Eruption sequestrum typically occurs in children aged 6–12 years during the eruption of permanent teeth, most commonly affecting the first and second molars. Patients often present with mild chewing discomfort, accompanied by localized gingival swelling and erythema around the erupting tooth [9]. A firm, white-to-yellowish mass (usually ≤ 5 mm in diameter) may be palpated in the central fossa of erupting permanent teeth, and is occasionally observed at the distal marginal ridge. Its morphology is generally irregular, though it may correspond to the occlusal anatomy of the tooth [2, 7]. Radiography reveals a small, isolated, high-density bony fragment located coronal to the erupting tooth, positioned outside the dental follicle while maintaining an intact follicular space around the tooth, with no evidence of alveolar crest disruption or extensive bone destruction. Microscopic analysis demonstrates non-viable lamellar bone tissue devoid of osteoblastic or osteoclastic activity, accompanied by mild inflammatory cell infiltration (predominantly lymphocytes and macrophages) in the adjacent connective tissue. In a case reported by Watkins [2], histopathologic examination revealed the presence of bacteria within ES. Schuler et al. [7] associated ES with the accumulation of dental plaque biofilm, suggesting that prolonged exposure could lead to tooth demineralization or dental caries. Kennedy [4] observed inflammatory tissue in the surrounding soft tissues, proposing that ES may contribute to gingivitis, pericoronal inflammation, and even hinder the eruption of permanent molars. Furthermore, a case report by Ho [6] indicated that soft tissues containing embedded ES hard tissue fragments may undergo further organization, ultimately developing into fibromas.