In recent decades, a considerable Improvement in endodontic methods, devices, and also in root canal filling materials, has occurred. Thus, patients as well as dental professionals are more inclined to favour tooth preservation over extraction of disputable teeth [
1,
2]. In consequence, since increased technical knowledge and scientific improvements have lead to higher treatment success rates, endodontic treatment and the subsequent restoration of the tooth should be considered as a therapy superior to implantation [
3,
4].
The choice of a biocompatible sealing material is crucial to the clinical success of endodontic therapy [
5]. Although sealers were developed to be confined within the root canal system, their extrusion over the apical constriction is frequently observed [
6,
7]. Therefore, these materials should have good biocompatibility and be well tolerated by the peri-apical tissues [
8]. The induction of a mild tissue reaction, together with cellular resorption of the sealing material in the case of extrusion over the apical foramen, needs to be evaluated. Several
in vitro, in vivo and clinical studies [
9‐
13] indicate that AH Plus, an epoxy resin-based root canal sealer, is suitable for successful endodontic therapy. This sealer remains popular despite its well-documented mutagenicity [
14], cytotoxicity and the induction of a severe inflammatory response [
15‐
17]. Besides cell dysfunctionality as a reaction to the epoxy resin-based sealing material [
16], an intense inflammation characterized by the presence of lymphocytes, macrophages, giant foreign body cells as well as necrotic bone fragments in maxilla of guinea pigs after AH Plus implantation was observed. Due to its severe initial inflammatory reaction that diminished over time but persisted throughout the entire observation period, the authors [
17] claim that this material does not possess enough biocompatible properties to be considered as an acceptable sealer for clinical use. Based on these contradictory results concerning an endodontic sealing material with a "gold standard" status [
13], the tissue reaction induced by alternative sealers needs to be investigated in similar study designs to decide upon their potential clinical usage. GuttaFlow is a relatively new sealing material, which combines gutta-percha and sealer into an injectable system. According to the manufacturer, this system is based on polydimethylsiloxane with added gutta-percha and nano-silver particles (< 30 μm). Due to its viscosity, it is more likely to be extruded into the peri-apical tissue when placed under pressure [
18]. However, it remains unclear which tissue reaction is caused by this material. In the study of AlAnezi
et al. [
19], the possible cytotoxicity of Endosequence BC Root Repair Material and grey and white MTA was evaluated. When exposed to these materials, the cells showed no significant difference in viability, while the cells in contact with AH 26 were significantly reduce in their viability.
Cleaning and shaping procedures are used to eliminate microorganisms from the root canal system during endodontic treatment. However, quite often a complete removal of bacteria is not possible [
20]. In such cases it would be desirable that sealing materials have antimicrobial properties. Using either the agar diffusion test or the direct contact test or both, different endodontic sealers have already been assessed for a possible antibacterial effect, most often measured against strains of
E. faecalis [
21‐
28].