Atividade antimicrobiana do óleo essencial da lippia origanoides e sua combinação com hidróxido de cálcio frente ao biofilme de candida albicans e enterococcus faecalis

Abstract

The use of intracanal medication is recommended in some cases to maximize the disinfection process and achieve successful endodontic treatment. Although calcium hydroxide is the most widely used medication today, there is still significant concern about its effectiveness due to cases of reinfection. Therefore, the search for vehicles that enhance the activity of calcium hydroxide has been increasing. The present study aims to evaluate the antimicrobial potential of Lippia origanoides essential oil (LOEO) and its association with calcium hydroxide powder on the 21-day multispecies biofilm of Enterococcus faecalis and Candida albicans. The oil from the leaves of L. origanoides was extracted by hydrodistillation and the chemical analysis of the constituents was performed by gas hromatography coupled with mass spectrometry. The antimicrobial activity of the oil was performed by broth microdilution to determine the minimum inhibitory concentration (MIC) and minimum lethal concentration (MLC). The synergistic effect of the natural compound with Chlorhexidine (CHX) was evaluated by the Checkerboard method, to determine whether the compounds would be tested associated or isolated. The antibiofilm activity was evaluated in vitro, based on tests with crystal violet, MTT and microscopy and ex vivo, where the multispecies biofilm was formed in roots of single-rooted human teeth and treatment was performed using Lippia origanoides essential oil, chlorhexidine and propylene glycol as vehicles for calcium hydroxide. To evaluate the antibiofilm activity in this test, microbiological collections were performed before and after treatments and then the colony forming units were counted. Cytotoxicity tests were performed with erythrocytes and fibroblasts. The results showed that the essential oil of L. origanoides has Thymol as its major compound (94.53%). Regarding antimicrobial activity, OELO presented MIC of 1.250 µg/ml for E. faecalis and 312 µg/ml for C. albicans. OELO and CHX did not present synergistic effects according to the ICIF calculation, despite having a reduction in the MIC of both compounds when combined. Therefore, it was decided to perform the antibiofilm tests with the compounds separately, using chlorhexidine only as a control. Regarding antibiofilm activity, the groups treated with essential oil, both in vitro and ex vivo, presented a greater reduction in the multispecies biofilm formed, being promising in endodontic therapy. Regarding hemolytic activity, the oil presented LC50 of 3,610 µg/ml, while chlorhexidine presented LC50 of 688 µg/ml, being the oil less toxic than CHX. In the fibroblast assay, the profile was similar, with the oil being less toxic than chlorhexidine. Based on the results of this study, it is possible to conclude that the essential oil of L. origanoides, as a vehicle for calcium hydroxide, exerted good antibiofilm effects against the mature biofilm of E. faecalis and C. albicans. Therefore, the essential oil of L. origanoides is a promising agent in the process of disinfection of the root canal system