The predominant cause of failure of endodontic treatment is because of resistant micro organisms such as E. faecalis, C. albicans and S. aureus [11]. Bioceramic (Endosequence BC) sealers are known for its antimicrobial property during setting and exhibits no shrinkage. During setting, there if formation of hydroxyapatite which chemically bonds to dentin and gutta percha [12]. MTA-based sealers (MTA Fillapex, Angelus, Brazil) are known for its properties such as remarkable biocompatibility, stimulating mineralization and exhibiting higher push-out strengths than zinc oxide eugenol cements [13]. MTA consists of calcium oxide which has similar mode of action to calcium hydroxide [14]. Epoxy resin-based sealers (AH Plus) have good antimicrobial, physical and chemical properties [15]. Hence, these sealers are diminishes the survival of microorganisms during obturation. The result of the present study showed significant microbial count reduction with Endosequence BC than MTA Fillapex and AH Plus for both time intervals (1 hr and 24hrs). It showed maximum antimicrobial efficacy against E.faecalis, followed by C.albicans and least against S.aureus. These outcome resembled with other studies where fresh Endoseq BC, MTA Fillapex and AH plus had antibacterial action against E. faecalis when tested by time kill assay [16]. The results also was in accordance in the studies in which ADT, DCT, and modified DCT were implemented [17, 18, 19, 20]. Endosequence BC showed least microbial count against E.faecalis, followed by C.albicans and least in S.aureus. The literature search does not have studies to support our result in relation to the highest reduction in Enterococcus faecalis followed by Candida albicans and Staphylococcus aureus using direct contact test. MTA Fillapex showed maximum antimicrobial efficacy against C.albicans followed by E.faecalis and least against S.aureus. AH Plus showed maximum antimicrobial efficacy against E.faecalis followed by S.aureus and showed no antimicrobial effect against C.albicans.
The antimicrobial property of the BC sealer is contributed by its alkaline pH that aids in exclusion of microorganisms like E.faecalis which cease to survive at high pH, near to 11.5 or more. Also active calcium hydroxide diffusion over the period of time can be the reason for the antimicrobial efficacy [21]. On contrary to our study, Hegde and Rathod (2017) stated that AH Plus sealer had better results than Bioceramic sealer against E.faecalis, in their study on Enterococcus faecalis. Such discrepancies can be due to the methodology used in the study which was agar diffusion test [22].
MTA Fillapex showed second most statistically significant microbial count reduction for both the time intervals, i.e 1 hour and 24 hours against C.albicans, E.faecalis and S.aureus. This result was in accordance to Rahman H et al (2017) who found that MTA Fillapex and Real Seal SE both showed antifungal activity whereas only MTA Fillapex was effective against E.faecalis, rest of the materials did not depict any antimicrobial activity [23]. Another study by Stowe et al (2013) verified the antimicrobial properties of MTA which inhibited the growth of both E. faecalis and Streptococcus sanguis [24]. MTA Fillapex which contains calcium silicate which on contact with the moisture from dentin, begins the hydration of calcium silicates. The calcium silicate hydrogel and calcium hydroxide gives the high pH which could be related to its antimicrobial property to MTA Fillapex. [25] On contrary to this study, Ustun et al. (2013) in his study showed that MTA based sealer has least antibacterial effect at 20 mins, whereas bioceramic sealer and epoxy resin sealer had maximum antibacterial properties [16]. AH Plus, resin based sealer, exhibited least antimicrobial efficacy against. Aravind et al (2006) evaluated the antimicrobial property five root canal sealers. The results showed that AH Plus has no antimicrobial action against Candida albicans and Enterococci [26]. The result of Andre Mickel et al (2003) was in accordance with our study, who also verified AH Plus to be show minimum efficiency against E.faecalis [27]. The ineffective property of AH Plus is because of the elimination of formaldehyde. The presence bisphenol A diglycidyl ether in resin based sealers induces its antimicrobial properties [23].
Our study showed a significant difference in antimicrobial properties observed in MTA Fillapex, AH Plus and Endosequence BC at one hour. The antimicrobial activity of tested sealers decreased over the time. This shows that resin based and bioceramic root canal sealers are more efficient in freshly mixed state and their antimicrobial properties decreases with time. However, the lowest long-time efficacy of AH Plus may be due to the paraformaldehyde released by this material only during setting period. Similar studies were also reported by Hyeder et al (2013) discussing the antimicrobial properties for AH Plus owing formaldehyde, which is released in small quantities during the setting reaction [23]. According to the manufacturers, the processing time of AH Plus is 4 hrs and setting time at 37 ◦C for another 8hr. Pizzo G et al (2006) suggested that the 24-h samples of AH Plus is ineffective in irradicating all E. faecalis in direct contact [28].