Cultured primary osteoblast viability and apoptosis in the presence of root canal sealers.

This study was designed to test the hypothesis that Roekoseal is less cytotoxic than eugenol-based Sealapex or calcium hydroxide-based Kerr’s Pulp Canal Sealer. Embryonic, day-19, rat calvarial osteoblasts were cultured at 4 10 5 cells/well. The concentration of conditioned medium from each sealer producing 50% surviving cells (ED50) was determined and long-term viability and apoptosis of cells assessed after exposure to the ED50 of each sealer. Low concentrations of Kerr’s Pulp Canal Sealer (190 mm 2 /1 ml) and high concentrations of Sealapex and Roekoseal (190 mm 2 /300 l) produced the ED50 .E D 50 challenged osteoblasts had fewer viable cells at 72 h than at 24 h, with significantly more viable cells in the Roekoseal group. There was significantly less apoptotic activity in cells exposed to Roekoseal ED50 than in cells exposed to Kerr’s Pulp Canal Sealer (p < 0.05) ED50. Roekoseal may be less cytotoxic than Kerr’s Pulp Canal Sealer, but further studies of this new sealer are required. Gutta-percha and sealers or cements have been used as the primary root canal filling materials for decades. Gutta-percha fills the major part of the cleaned and shaped root canal system. However, voids are present because the gutta-percha does not adapt fully to the canal irregularities. The purpose of the root canal sealer is to fill the voids and canal irregularities and to enhance adaptation of the gutta-percha to the canal walls (1). During root canal obturation techniques, sealers may be extruded into the periradicular area through a large apical foramen, accessory and lateral canals, and dentinal tubules. In doing so, they come in direct contact with the periodontal ligament, alveolar bone, neurovascular structures, and inflammatory cells that may be present when the periradicular tissues are under the influence of microbial contamination. The presence of root canal sealers in these tissues may be highly deleterious (2). Root canal sealers are not fully biocompatible and can cause significant amounts of cell death in cell cultures. Numerous studies have examined the cytotoxic effects of root canal sealers on gingival and periodontal fibroblasts, osteoblasts, subcutaneous tissues, macrophages, and nerve cells (3–11). These effects were examined using various methods, including cell culture, in vivo implantation in the subcutaneous tissues, in vitro nerve electrophysiological studies, and histological analysis of periradicular tissues (10 –26). However, when cell cultures were used in screening studies for sealers, the results focused on the number of cells that immediately die as a result of exposure to different sealers (3–26). On the other hand, factors associated with the continued viability of cells that survive the challenge by sealers and factors such as apoptosis (27–29) have not been investigated. Therefore, it is important to determine the effect of sealers on the viability of the periradicular tissues and cells that survive the initial exposure to the materials. The purpose of this study was to test the hypothesis that a calcium hydroxide sealer and a zinc oxide-eugenol sealer are more cytotoxic than a polydimethylsiloxane-based root canal sealer on continued cell viability and apoptosis in primary osteoblasts.