Eruption Sequestrum-Case Report and Histopathological Findings

Eruption sequestrum (ES) is an uncommon condition first reported as an osseous fragment overlying the crown of an erupting permanent molar prior to or immediately after the emergence of the cuspal tips through the oral mucosa (1). ES consists of a small irregular bone spicule, but it can also correspond to the occlusal anatomy of teeth (2). The position of this spicule overlies directly the central occlusal fossa, but within the soft tissue (3). ES may also be retained by tissue covering the distal marginal ridge of an erupting tooth (2). ES is usually observed at the time of eruption of the mandibular first molars, but it has been noted occurring with maxillary first molars and mandibular second molars (1,2). This major occurrence in mandibular first molars Eruption Sequestrum Case Report and Histopathological Findings


INTRODUCTION
Eruption sequestrum (ES) is an uncommon condition first reported as an osseous fragment overlying the crown of an erupting permanent molar prior to or immediately after the emergence of the cuspal tips through the oral mucosa (1). ES consists of a small irregular bone spicule, but it can also correspond to the occlusal anatomy of teeth (2). The position of this spicule overlies directly the central occlusal fossa, but within the soft tissue (3). ES may also be retained by tissue covering the distal marginal ridge of an erupting tooth (2).
ES is usually observed at the time of eruption of the mandibular first molars, but it has been noted occurring with maxillary first molars and mandibular second molars (1,2). This major occurrence in mandibular first molars can be due to these teeth with an ectopic path of eruption, with the mesial cusps at some stage lying mesial to the distal root of the second primary molar (3). Thus, a small osseous fragment can occasionally separate from the contiguous bone and emerge through the alveolar bone. In most cases, the small bone fragments are absorbed completely prior to eruption of the molar. However, when the fragments are large or the eruption speed is slow, small bone fragments on the occlusal surface remain unresorbed and exposed to the mucosa prior to molar eruption, which forms ES (1). This can occur due to reduction of osteoclast activity and of bone resorption mediated by dental follicle during tooth eruption caused by apoptosis of reduced enamel epithelium (4).
ES is a mass coronally of the erupting tooth with broader borders (3). If seen radiographically before tooth eruption, its intraoral appearance may be predicted (1).
Although ES has been reported as a fragment consisting of compact, non-viable bone (1,2,5), Watkins (3) described a case composed of dentin and covered in areas by fragments of bacteria-infected cementum. Thus further investigations should be performed to elucidate its microscopic aspects. The aim of this paper is to report a case of unilateral ES in a 7-year-old Brazilian boy and to describe its histopathological findings.

CASE REPORT
A 7-old boy was referred to the Pediatric Dentistry Clinic of Ribeirão Preto Dental School, University of São Paulo, Brazil for routine dental treatment. No significant medical condition was reported. There was neither history of oral-facial trauma nor abnormalities upon extraoral examination. Informed written consent was obtained from the patient's mother and this report was approved by the institutional Ethics Committee (Protocol #2010.1.532.58.6). Figures 1 to 3 illustrate the clinical and histopathological features of the case.
Intraoral examination revealed a small white fragment, approximately 0.5 cm in diameter, with hard consistency and irregular shape, located on the occlusal surface of the erupting mandibular right first molar (Fig. 1). There was neither history of pain nor evidence of dental caries or abnormality in other soft tissues. Periapical radiograph did not show adequately this fragment. The treatment plan included surgical removal of this fragment. A biopsy of the area was excised under local anesthesia. The extracted fragment   was preserved in formalin for 72 h and submitted to histological processing for microscopic analysis.
The biopsy tissue was composed of a 0.4 x 0.3 x 0.3 cm bone tissue. The microscopic analysis showed non-viable bone tissue of large trabeculae with empty lacunae, evidenced by lack of osteocytes in the lacunae. A minimal amount of existing spongy bone consisted of acute inflammatory cells infiltrate (neutrophils). Signs of necrosis were observed on the periphery. However, no signs of viable bone were evident throughout the specimen. The histological diagnosis was ES (Fig. 2).
At the 1-week postoperative appointment, the patient was evaluated clinically, although no significant signs and symptoms were revealed. After completion of the treatment, follow-up visits were scheduled every 6 months for monitoring dental plaque control as well as for clinical and radiographic assessment (Fig. 3), revealing normal postoperative conditions.

DISCUSSION
ES is an uncommon clinical finding. It is usually associated with the permanent mandibular first molar (1,3,5-7), as described in the patient of this case.
Although previously thought to have little clinical significance (1), ES may retain biofilm accumulation and lead to pericoronitis, localized swelling, discomfort during mastication, and demineralization or dental caries if it remains for a prolonged time (2). In addition, Maki et al. (9) observed chronic inflammatory alterations in the gingiva in contact with bone and Ho (8) reported a fibromatosis with embedded bone fragment. As its early recognition is important for preventing a future inadequate surgical intervention, the fragment was removed surgically in this patient, as in other cases (2).
In an unusual case of ES, the specimen consisted of a small irregular calcified mass, composed of dentin and covered in areas by fragments of bacteria-infected cementum (3). In the same case, histopathological examination showed non-vital bone, as reported elsewhere (1,2,5). Spongy osseous tissue with an inflammatory cell infiltrate and empty lacuna-like spaces were also identified, in accordance to similar preliminary findings (7). Although ES is rare, it is important to describe its clinical and histological findings for helping clinicians diagnose this condition and updating microscopic descriptions.