Histo-Pathological Assessment of Zinc Oxide Eugenol Canal Sealer on Periodontal Tissues: Three Case Reports

Purpose: Sealers used in endodontic dental treatment may leak into the periradicular tissues, increasing the risk of retained particles in oral mucosa, tissue irritation or discoloration, delayed healing or interfering on the erupting permanent teeth. Three clinical cases of primary teeth pulpectomy using Zinc Oxide Eugenol (ZOE) paste were observed, showing retained particles of filling cement in the oral mucosa during permanent dentition eruption. The aim of the study was to histologically analyze the possible causes of discoloration and to assess the effects of the sealer on cells by evaluating ultrastructure. Materials and Methods: Three healthy children undergoing orthodontic therapy were enrolled in this study for the presence of gingival pigmentation. For all patients a biopsy of the discolored area was performed and histologically analyzed. Furthermore, sealer was added to the culture of SAOS-2 to evaluate cytotoxicity effects by Alamar blue tests and ultrastructure evaluation using Transmission Electrons Microscope (TEM). Results: Black extracellular granules were appreciable in all Hematoxylin Eosin-stained sections. Deposition of pigment was observed particularly in the blood vessel walls, in connective tissue and in intercellular ground substance. In cell culture, sealers reduced viability about 43% after 24h, 17% after 48h and 12% after 72h compared with untreated cells. Furthermore, sealer affected morphology creating vacuoles inside the cytoplasmic area. Conclusions: Sealer resulted to be mild toxic for the cells. Retention granules of bismuth in the oral mucosa after root canal treatment of deciduous teeth and subsequent mucosal discoloration analyzed in this study should alert pediatric dentists to use the filling materials very carefully and to check the radicular and filling paste resorption in order to prevent the prolonged retention of the overfilled material.