1. Introduction
he success of endodontic treatment depends on the complete elimination of pathogenic bacteria inside the root canal [2]. Washing is a required endodontic method for removing microorganisms from the root canal system [6]. Recently, the use of natural products as root canal disinfectants has been extensively studied due to their efficiency, safety, availability [9], and the inability of microorganisms to develop resistance to the materials [10]. The Thyme inhibits the growth of bacteria in the oral cavity. It can prevent dental infections due to compounds such as flavonoids, saponins, and bitter substances [12, 13]. The outstanding Myrtus had acceptable antimicrobial properties due to its polyphenolic compounds and essential oils against endodontic pathogens, especially Enterococcus faecalis [19]. Limited studies have been done on Myrtus microemulsion or Thyme microemulsion as a root canal rinse, and no comparison between them.
2. Materials and Methods
In this laboratory study, 25 extracted root canals in human anterior teeth, randomly divided into 5 groups (in equal numbers), were used. Next, they were rinsed with sodium hypochlorite (NaOCI) 2.5%, Myrtus 10% microemulsion, Thyme 0.6%microemulsion, with positive group control (impregnation with E. faecalis suspension and rinsing with normal saline) and negative control group (non-impregnation with E faecalis suspension and rinsing with normal saline). The teeth were then filled with gutta-percha and incubated at 37°C for 90 days. Then sampling was performed, and samples were examined for colony count. Finally, the comparison of bacterial colony count in the groups due to abnormal data distribution was performed using the Kruskal-Wallis test.
3. Results 
The results showed that the highest positive culture belonged to the Thyme 0.6% microemulsion group; the lowest belonged to the Sodium hypochlorite (NaOCI) 2.5% group.
The antimicrobial effect of Thyme 0.6% cleanser on E. faecalis was 20%, and 80% did not affect the growth of this bacterium. The antimicrobial effect of Myrtus 10% cleanser on E. faecalis was 88%, and 12% did not affect the growth of this bacterium. The antimicrobial effect of Sodium hypochlorite (NaOCI) 2.5% cleanser on E. faecalis was 93%, and 7% did not affect the growth of this bacterium. The mean number of colonies between groups was not statistically significant.
4. Discussion and Conclusion
A successful root canal treatment consists of three stages of clearing and shaping the canal, disinfecting, and filling its three-dimensional space [33, 34]. Due to the resistance of bacteria to synthetic chemical drugs and the need to produce various plant antimicrobials in this study, the antimicrobial effect of Thyme 0.6% microemulsion, Myrtus 10% microemulsion, and NaOCI 2.5% against E. faecalis after filling the root canal was examined. The present study results showed that the highest mean colony was in the Thyme microemulsion group, and the lowest was in the NaOCI group. The mean number of settlements between groups was not statistically significant.
According to the results, it can be said NaOCI 2.5% had the highest antimicrobial properties against E. faecalis and showed the lowest colony growth rate, while Myrtus 10% microemulsion and Thyme 0.6%microemulsion in the second and third ranks.

Ethical Considerations
Compliance with ethical guidelines
The Ethics Committee of Arak University of Medical Sciences approved this study (Code: IR.ARAKMU.REC.2019.297).

Funding
This research did not receive any grant from funding agencies in the public, commercial, or non-profit sectors. 

Authors' contributions
All authors equally contributed to preparing this article.

Conflicts of interest
The authors declared no conflict of interest.

Acknowledgements
The collaborators of Arak University of Medical Sciences in conducting this research are thanked and appreciated.
 


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