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Article

Antibacterial and Antibiofilm Effect of Lavandula dentata L. Essential Oil as Endodontic Irrigant Against Standard and Clinical Strains of Enterococcus spp.

by
Caroline Trefiglio Rocha
1,
Patrícia Michelle Nagai de Lima
2,
Thaís Cristine Pereira
2,
Lara Steffany de Carvalho
2,
Mariana Gadelho Gimenez Diamantino
1,
Amjad Abu Hasna
1,3,
João Carlos da Rocha
4,
Luciane Dias de Oliveira
2,* and
Cláudio Antonio Talge Carvalho
1
1
Department of Restorative Dentistry, Endodontics Division, Institute of Science and Technology, São Paulo State University (ICT-UNESP), São José dos Campos 12245-000, SP, Brazil
2
Department of Biosciences and Oral Diagnosis, Institute of Science and Technology, São Paulo State University (ICT-UNESP), São José dos Campos 12245-000, SP, Brazil
3
School of Dentistry, Universidad Espíritu Santo, Samborondón 092301, Ecuador
4
Department of Social and Pediatric Dentistry, Institute of Science and Technology, São Paulo State University (ICT-UNESP), São José dos Campos 12245-000, SP, Brazil
*
Author to whom correspondence should be addressed.
Appl. Sci. 2025, 15(10), 5534; https://doi.org/10.3390/app15105534
Submission received: 15 March 2025 / Revised: 1 May 2025 / Accepted: 5 May 2025 / Published: 15 May 2025
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Abstract

:
Enterococcus faecalis and Enterococcus faecium are frequently associated with persistent endodontic infections due to their ability to form biofilms and resist conventional treatments. The aim of this study was to evaluate the antibacterial and antibiofilm effects of Lavandula dentata L. essential oil at 100% against the standard and clinical strains of Enterococcus spp. The minimum bactericidal concentration (MBC) of L. dentata essential oil for each bacterial strain was determined. The antibiofilm effect was evaluated by an MTT assay. Data were statistically analyzed by the ANOVA and Tukey test, with a significance level of 5%. The MBC value was 32% (292.8 mg/mL) against all the tested strains. L. dentata significantly reduced E. faecalis and E. faecium biofilms at 16–64% (146.4–585.6 mg/mL) concentrations, with effects comparable to 2% chlorhexidine (CHX) (p ≥ 0.05). Biofilm reduction was strain-dependent at 30 min but showed broader efficacy after 24 h, particularly against E. faecium clinical strains (p ≤ 0.001). L. dentata demonstrated effective antimicrobial activity against planktonic and biofilm forms of E. faecalis and E. faecium as it reduced biofilm formation at a concentration of 16% and 64% (146.4 and 585.6 mg/mL), with results comparable to 2% CHX after 30 min and 24 h. L. dentata EO may serve as a potential alternative or adjunctive antimicrobial agent in endodontic treatment. However, the study’s limitations included the in vitro design and lack of cytotoxicity assessment.

1. Introduction

Enterococcus spp. has undergone several taxonomic revisions before ultimately being designated by this name [1]; belongs to a group of microorganisms known as lactic acid bacteria (LAB); and is characterized as Gram-positive, facultative anaerobic cocci that occur singly, in pairs, or in chains [2]. One of its most notable characteristics is its remarkable ability to survive and adapt to a wide range of environmental conditions that are typically unfavorable to other bacterial species. This adaptability provides Enterococcus spp. with a significant ecological advantage, allowing it to persist in hostile environments and facilitating its dissemination in various habitats, including the human oral cavity [3,4,5].
Among the species within this genus, Enterococcus faecalis and Enterococcus faecium are of clinical relevance due to their frequent association with endodontic and periodontal infections. These microorganisms have been widely detected in the root canal system of teeth diagnosed with periapical periodontitis, where they are known to contribute to persistent infections and endodontic treatment failure. Additionally, they have been isolated from subgingival biofilms in patients with periodontitis and gingivitis, suggesting a role in the pathogenesis and progression of periodontal disease. Their ability to survive harsh conditions, including high pH levels, low oxygen availability, and antimicrobial challenges, further underscores their clinical significance in dentistry [6,7].
Over the past two decades, numerous studies have investigated the role of Enterococcus faecalis in persistent endodontic infections. Its ability to form resilient biofilms, penetrate dentinal tubules, and survive in nutrient-deprived environments has been well-documented [6,7]. In contrast, Enterococcus faecium, although less frequently studied in the context of endodontics, is emerging as a significant pathogen due to its increasing antimicrobial resistance and adaptability (Kristich et al., 2014 [8]; Boccella et al., 2021 [9]). Most of the existing research has focused on E. faecalis, with limited attention paid to E. faecium, despite its growing clinical relevance.
During the root canal treatment of infected teeth, the main goal is to eliminate the microbial load, including E. faecalis and E. faecium, by cleaning and shaping the root canal system [10] using mechanical instruments, chemical agents like sodium hypochlorite [11], and intracanal medications [12]. However, biofilm formation by Enterococcus spp. in the root canal system exhibits high resistance to biomechanical preparation and intracanal medication, while also modulating the host’s immune response. The persistent presence of biofilm within the root canal contributes to the failure of complete microbial elimination, serving as a key factor in the persistence of periapical lesions [13].
Given the persistent challenge of microbial resistance in endodontics, the search for new and more effective antimicrobial agents remains an ongoing priority. In this context, the use of herbal medicines is gaining increasing attention [14], and in particular the application of essential oils [15,16]. To overcome the limitations of conventional disinfectants, such as cytotoxicity and incomplete biofilm elimination, several studies have explored plant-derived essential oils for their antimicrobial potential in endodontics. Essential oils from Melaleuca alternifolia (tea tree), Origanum vulgare (oregano), Thymus vulgaris (thyme), and Cymbopogon citratus (lemongrass) have demonstrated varying degrees of success in inhibiting E. faecalis and other endodontic-related microorganisms in both planktonic and biofilm forms [16,17,18,19].
Lavandula dentata L., commonly known as French lavender or toothed lavender, is a flowering plant of the Lamiaceae family, native to the Mediterranean basin, Eritrea, Ethiopia, Yemen, and the Arabian Peninsula as documented by the Board of Trustees of the Royal Botanic Gardens, Kew [20]. L. dentata essential oil has exhibited antifungal activity against strains of Candida albicans [21], and antibacterial activity against Gram-positive and Gram-negative bacterial strains [22,23,24].
Despite these promising antimicrobial properties, studies specifically evaluating the efficacy of L. dentata essential oil against Enterococcus species remain scarce. In addition, while L. dentata essential oil has been tested against E. faecalis, no studies have specifically investigated its activity against E. faecium. This is an important distinction, as E. faecium exhibits greater antimicrobial resistance and adaptability compared to E. faecalis [8,9]. Our study fills this gap by providing the first data on the susceptibility of E. faecium to L. dentata essential oil, which could have implications for endodontic infections where this species is present. To the best of our knowledge, only one study has assessed its antibacterial effect against E. faecalis using disk diffusion and broth microdilution methods, reporting that the oil was effective [25]. However, no studies have been conducted to date to evaluate its antimicrobial activity against E. faecium. Considering that biofilms are the primary mode of bacterial persistence in endodontic infections, our study uniquely assesses the antibiofilm effects of L. dentata essential oil against both E. faecalis and E. faecium, providing new insights into its potential as an adjunct in endodontic disinfection. Still, further research is needed to explore its potential as an alternative therapeutic agent in endodontics.
In this study, the antibacterial or antiplanktonic effect was evaluated by determining the minimum bactericidal concentration (MBC) values, and the antibiofilm was evaluated by the MTT assay: these methods are widely accepted in the literature to evaluate the antibacterial and antibiofilm action of herbal medicine [26,27].
Therefore, the aim of this study was to evaluate the antibacterial and antibiofilm effects of L. dentata essential oil against standard and clinical strains of E. faecalis and E. faecium. The null hypothesis was that L. dentata essential oil has no effect against the tested strains of E. faecalis and E. faecium.

2. Materials and Methods

2.1. Essential Oil Selection

The essential oil of Lavandula dentata was used at a concentration of 100%, obtained from the company (Lavanda Brasil, WNF Óleos Essenciais, São Paulo, SP, Brazil). According to the manufacturer, it originates from Monte Verde, MG, Brazil, and is extracted through steam distillation from the aerial parts of the plant. The controlled parameters confirmed that the oil had a pale yellow color, a characteristic lavender odor, and a clear liquid appearance, with no detected impurities. Its density was measured at 0.915 g/cm3, and its refractive index was 1.468, both of which fell within the expected specification range. The chromatographic analysis (GC/MS) was performed using a Shimadzu GCMS-QP2010 Plus, under specific analytical conditions, including an injection temperature of 250 °C, helium as the carrier gas, and a capillary column DB-5MS (30 m × 0.25 mm × 0.25 μm). The results revealed that the main chemical constituents of the essential oil included 1,8-Cineole (62.02%), β-Pinene (17.71%), Linalool (7.33%), α-Pinene (6.44%), and Pinocarveol (2.52%), along with minor compounds such as camphene (0.55%), β-Phellandrene (1.81%), β-Myrcene (0.92%), and p-Cymene (0.69%). Based on these results, the essential oil was approved in accordance with analytical quality standards. These characteristics were provided by the manufacturer, and no phytochemical analysis was performed by our team, as the characterization of the essential oil was carried out by the manufacturer.

2.2. Selection of Bacterial Strains

This study used both standard and clinical strains of Enterococcus faecalis and Enterococcus faecium. Standard strains of Enterococcus faecalis (ATCC 4083) and Enterococcus faecium (ATCC 6569) obtained from the American Type Culture Collection (ATCC) (Rio de Janeiro, RJ, Brazil) were used. In addition, clinical strains were isolated from teeth with endodontic infections and collected in a previous study [28]. The strains were nominated (E. faecalis 1, 2, 3, and 4.1, and E. faecium 4.2 and 7.3). The antibiotic resistance profile of these strains was established by the same study as in Table 1.
The identified strains were stored in Eppendorf tubes containing 80% Brain Heart Infusion (BHI) broth and 20% glycerol at −80 °C in the Microbiology and Immunology Laboratory of the Institute of Science and Technology of São José dos Campos (ICT/UNESP), with prior registration in SisGen. Identification was performed using the multiplex polymerase chain reaction (PCR) method. Antimicrobial susceptibility was assessed by the E-test.

2.3. Antibacterial Evaluation of L. dentata Essential Oil Against the Selected Strains

The minimum bactericidal concentration (MBC) of L. dentata essential oil for each bacterial strain was determined using the broth microdilution technique, following the Clinical and Laboratory Standards Institute (CLSI) M7-A6 guidelines. L. dentata essential oil was diluted in Tween 20 at a concentration of 0.05%. This solution was further diluted in Mueller–Hinton broth (HiMedia®, Mumbai, India) to achieve the desired concentrations. The assay was conducted in microplates, where 100 μL of Mueller–Hinton broth and 100 μL of essential oil were added to the first well. A series of ten serial dilutions were then carried out.
Following the E L. dentata essential oil dilution, microbial suspensions were prepared. E. faecalis and E. faecium were separately cultivated on BHI agar (HiMedia Laboratories Private Ltd., Mumbai, India) for 24 h. At the time of standardization, bacterial suspensions were adjusted to a concentration of 10⁶ CFU/mL in saline solution (Eurofarma Laboratórios S.A., São Paulo, Brazil), using a spectrophotometer (Micronal S. A., São Paulo, Brazil). Then, 100 μL aliquots of each microbial suspension were added to all wells. The test was conducted in duplicate.
Sterility controls included Mueller–Hinton broth alone and Mueller–Hinton broth with 0.05% Tween 20. Negative controls consisted of Mueller–Hinton broth with 0.05% Tween 20 and bacterial suspension, as well as Mueller–Hinton broth with bacterial suspension only.
To determine the MBC of L. dentata essential oil, 100 μL from each well was plated onto BHI agar in Petri dishes, which were pre-marked according to the corresponding L. dentata essential oil dilutions. After 48 h of incubation, the MBC was defined as the lowest L. dentata essential oil concentration at which no bacterial colony growth was observed. The experiment was performed in duplicate.

2.4. Antibiofilm Evaluation of L. dentata Essential Oil Against the Selected Strains

For biofilm formation, 100 μL of BHI broth and 100 μL of each standardized bacterial suspension (108 CFU/mL in physiological solution) were added to 96-well microtiter plates. The plates were then incubated at 37 °C for 48 h without shaking, under static conditions, with the culture medium replaced every 24 h to maintain adequate nutrient availability. After incubation, the wells were washed three times with sterile saline to remove non-adherent bacteria. Cells that remained adhered to the surface were considered true biofilms.
The formed biofilms were treated with 100 µL of L. dentata essential oil at the concentrations of ½ × MBC, MBC, and MBC × 2. In addition, 100 μL/well of a sterile liquid culture medium (BHI broth) was added. Sterility control with culture medium alone, a negative control with culture medium and bacterial suspension, and a 2% chlorhexidine (CHX) treatment control (Biofórmula Manipulação, São José dos Campos, SP, Brazil) were included in the assay.
Following treatments, for 30 min or 24 h, the antibiofilm activity of the essential oil was assessed by evaluating the metabolic activity of microorganisms using the MTT assay, in which the wells were washed once with saline solution, and 200 μL of MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide) solution was added to each well. The plate was then incubated in the dark at 37 °C for 1 h. After incubation, the MTT solution was removed, and 200 μL of Dimethylsulfoxide (DMSO) was added, followed by incubation at 37 °C for 10 min with additional shaking for another 10 min. Optical densities (OD) were then measured using a microplate reader at 570 nm and converted into the percentage of microbial metabolic activity using the formula:
%   m e t a b o l i c   a c t i v i t y = O D   t r e a t e d   g r o u p × 100 m e d i u m   O D   c o n t r o l   g r o u p

2.5. Statistical Analysis

The data obtained in the in vitro tests had a normal distribution and were statistically analyzed by the ANOVA method complemented by the Tukey test, with a significance level of 5% (p ≤ 0.05).

3. Results

3.1. Antibacterial Effect of L. dentata Essential Oil Against the Selected Strains

The MBC value of the L. dentata essential oil was 32% against all the tested standard and clinical strains of E. faecalis and E. faecium.
To convert the MBC value (32%) into mg/mL, we used the formula:
M B C   ( m g / m L ) = M B C   ( % ) × D e n s i t y   ( m g / m L ) 100
Given data:
MBC (%) = 32%, density = 0.915 g/cm3 = 915 mg/mL, and thus the MBC was 292.8 mg/mL.

3.2. Antibiofilm Effect of L. dentata Essential Oil Against the Selected Strains

After 30 min of treatment, L. dentata essential oil was effective in reducing the biofilm formation of E. faecalis ATCC and the clinical strains 1, 2, 3, and 4.1 at the concentrations 16% (146.4 mg/mL) and 64% (585.6 mg/mL) with no statistically significant difference to the 2% CHX group (p ≥ 0.05), and with a statistically significant difference to the control group (p ≤ 0.001), except for the clinical strain 4.1 as shown in Figure 1. Conversely, L. dentata essential oil was effective in reducing the biofilm formation of E. faecium ATCC and the clinical strain 7.3 at the concentrations 16% (146.4 mg/mL) and 64% (585.6 mg/mL) with no statistically significant difference to the 2% CHX group (p ≥ 0.05), with a statistically significant difference to the control group (p ≤ 0.001), and against E. faecium clinical strain 4.2 at the concentrations 32% (292.8 mg/mL) and 64% (585.6 mg/mL) with no statistically significant difference to the 2% CHX group (p ≥ 0.05), as shown in Figure 1.
After 24 h of treatment, L. dentata essential oil was effective in reducing the biofilm formation of E. faecalis ATCC and the clinical strain 1 and 4.1 at the concentrations 16% (146.4 mg/mL) and 32% (292.8 mg/mL) with no statistically significant difference to the 2% CHX group (p ≥ 0.05), and with a statistically significant difference to the control group (p ≤ 0.001), as shown in Figure 2. Furthermore, it was effective in reducing the biofilm formation of E. faecalis clinical strains 2 and 3 at all concentrations, with a statistically significant difference to the control group (p ≤ 0.001), as shown in Figure 2. In addition, it was effective in reducing the biofilm formation of E. faecium ATCC and the clinical strains 4.2 and 7.3 at all the tested concentrations, with a statistically significant difference to the control group (p ≤ 0.001), as shown in Figure 2.

4. Discussion

The microorganisms involved in intracanal infections exhibit high virulence, as they can colonize the root canal system, infiltrate dentin walls, and form bacterial biofilms [29]. These biofilms serve as a crucial adaptive mechanism, enabling microbial survival despite environmental changes induced by endodontic treatment [13,30]. Hence, this study aimed to evaluate the antibacterial and antibiofilm effect of L. dentata essential oil against standard and clinical strains of E. faecalis and E. faecium. The selection of both bacteria was based on the literature associating Enterococcus spp. with the persistence of periradicular lesions following endodontic treatment. Gomes et al. (2021) [31] reported a higher prevalence of E. faecalis in canals with persistent infections, using both culture growth and PCR techniques for detection. Additionally, Murad et al. (2014) [32] identified E. faecium and Staphylococcus epidermidis as more prevalent in persistent endodontic lesions, employing the DNA hybridization technique. Nevertheless, recently there has been a scarcity of studies linking E. faecium to endodontic infections, likely due to the limited number of investigations utilizing DNA hybridization to differentiate Enterococcus species [33].
The phytochemical profiles of L. dentata essential oils reported in the literature exhibit variability due to differences in major compounds, likely influenced by biological and environmental factors, as well as the time of harvest [34]. However, in another study [35], it was found that L. dentata harvested from different regions of Brazil contained similar compounds, including analogs reported in previous studies, ensuring consistency with the essential oil used in this study. According to the literature, L. dentata essential oil is predominantly composed of oxygenated monoterpenes, particularly eucalyptol (1,8-cineole) [21,36]. According to [36], it was reported that oxygenated monoterpenes constituted 90.38% of L. dentata EO, followed by 7.38% monoterpene hydrocarbons. Similarly, according to [21], it was identified that 1,8-cineole (eucalyptol) and β-pinene were the most abundant compounds. The L. dentata essential oil tested in this study demonstrated a comparable composition, with 62.02% 1,8-cineole and 17.71% β-pinene, as reported by the manufacturer. It is worth noting that Eucalyptol (1,8-cineole) is an oxygenated monoterpene with documented antimicrobial activity [37]. In the present study, bacterial inhibition was observed, suggesting that the high concentration of 1,8-cineole (62.02%) contributed to the antimicrobial effect against both clinical and standard strains of E. faecalis and E. faecium.
It is important to emphasize that the phytochemical variability in essential oils can indeed influence the outcomes of the study, as the composition of essential oils may vary depending on factors such as plant origin, harvesting conditions, and extraction methods. This variability could lead to differences in the antimicrobial efficacy of L. dentata essential oil across different batches. For this reason, the essential oil of Lavandula dentata was used with a concentration of 100%, obtained from the company (Lavanda Brasil, WNF Óleos Essenciais, São Paulo, SP, Brazil).
In our antibacterial evaluation, L. dentata essential oil at a concentration of 32% (292.8 mg/mL) demonstrated significant efficacy in inhibiting the growth of both E. faecalis and E. faecium. However, when lower concentrations of the essential oil were tested, bacterial growth was observed across all the strains, indicating that these concentrations were insufficient to inhibit microorganisms. The minimum inhibitory concentration (MIC) test, which would typically allow for the determination of the lowest concentration of the essential oil capable of preventing bacterial growth, could not be performed. This was attributed to the fact that the process of homogenizing L. dentata essential oil with Tween 20, followed by mixing it with the Mueller–Hinton medium, resulted in the development of turbidity. This turbidity rendered it impossible to visually assess bacterial inhibition through standard optical methods, thus preventing the reliable determination of the MIC.
The present study demonstrated that L. dentata essential oil at concentrations of 16% (146.4 mg/mL) and 64% (585.6 mg/mL) led to a reduction in the bacterial load of monotypic biofilms of the standard and clinical strains of E. faecalis and E. faecium, being as effective as the 2% CHX group after 30 min. According to another study, L. dentata essential oil at concentrations of 1.5–6% can inhibit or prevent the formation of E. faecalis biofilms [25]. To the best of our knowledge, there were no studies in the literature that evaluated the antibacterial or antibiofilm effect of L. dentata essential oil against E. faecium. Nevertheless, L. dentata essential oil was effective in reducing the biofilm formation of Escherichia coli, Candida albicans, and Streptococcus pyogenes [22]. Additionally, in the present study, after 24 h of treatment, L. dentata essential oil at the concentrations of 16% (146.4 mg/mL) and 32% (292.8 mg/mL) was effective in reducing the biofilm formation of the standard and clinical strains of E. faecalis and E. faecium with a statistically significant difference in the control group.
The observed higher biofilm eradication at 30 min compared to 24 h for some Enterococcus strains could be attributed to the immediate antimicrobial action of L. dentata essential oil upon contact. Essential oils contain volatile and highly active compounds that can exert rapid bactericidal effects. However, over extended periods, factors such as compound evaporation, degradation, or interaction with biofilm matrix components may reduce their sustained efficacy. Additionally, biofilm dynamics and bacterial stress responses could influence the long-term effects of the treatment. Future studies with time-kill kinetics and extended exposure durations will help further clarify the temporal efficacy of L. dentata essential oil against biofilms.
According to Vijayakumar et al. (2020) [37], the antimicrobial action of eucalyptol occurs by preventing bacterial adhesion, thereby interfering with the initial biofilm formation. This mechanism justifies the observed bacterial load reduction when exposed to L. dentata essential oil, which is crucial for successful endodontic treatment. As stated by Siqueira and Rôças (2008) [38], an ideal endodontic procedure aims to reduce bacterial load to subcritical levels compatible with the healing of persistent lesions. Further studies are needed to precisely quantify these subcritical levels in relation to wound healing.
Finally, this is the first study to evaluate the antimicrobial activity of Lavandula dentata essential oil against both clinical and standard strains of E. faecalis and E. faecium isolated from persistent root canal infections. Our findings demonstrate that L. dentata EO exhibited antibacterial activity against antibiotic-resistant microorganisms within 30 min and maintained its effect over 24 h. The 16% (146.4 mg/mL) concentration appears to be the most suitable, suggesting its potential use as an adjunctive chemical agent in endodontic treatment. Given the frequent renewal of irrigants during root canal procedures, the volatile components of L. dentata essential oil would have increased interaction with bacterial biofilms. Additionally, its use as a vehicle for intracanal medication could be considered, as it effectively reduced bacterial load within 24 h. However, as a limitation, this is an in vitro study, and further in vivo research is necessary to validate these findings before clinical application can be recommended. In addition, this study used commercially obtained essential oils, and no chemical standardization was performed to verify the components reported by the manufacturer.

5. Conclusions

L. dentata essential oil (EO) exhibited effective antimicrobial activity against both planktonic and biofilm forms of E. faecalis and E. faecium. The minimum bactericidal concentration (MBC) was determined to be 32% (292.8 mg/mL) for all strains tested. Furthermore, L. dentata EO significantly reduced the biofilm formation of both E. faecalis and E. faecium at concentrations of 16% (146.4 mg/mL) and 64% (585.6 mg/mL). These effects were comparable to those observed with the 2% chlorhexidine (CHX) treatment after both 30 min and 24 h of exposure.

Author Contributions

Conceptualization, C.T.R., P.M.N.d.L., T.C.P., L.S.d.C., M.G.G.D., A.A.H., J.C.d.R., L.D.d.O. and C.A.T.C.; methodology, C.T.R., P.M.N.d.L., T.C.P., L.S.d.C., M.G.G.D., A.A.H., J.C.d.R., L.D.d.O. and C.A.T.C.; software, C.T.R., P.M.N.d.L., T.C.P., L.S.d.C., M.G.G.D., A.A.H., J.C.d.R., L.D.d.O. and C.A.T.C.; validation, C.T.R., P.M.N.d.L., T.C.P., L.S.d.C., M.G.G.D., A.A.H., J.C.d.R., L.D.d.O. and C.A.T.C.; formal analysis, C.T.R., P.M.N.d.L., T.C.P., L.S.d.C., M.G.G.D., A.A.H., J.C.d.R., L.D.d.O. and C.A.T.C.; investigation, C.T.R., P.M.N.d.L., T.C.P., L.S.d.C., M.G.G.D., A.A.H., J.C.d.R., L.D.d.O. and C.A.T.C.; resources, C.T.R., P.M.N.d.L., T.C.P., L.S.d.C., M.G.G.D., A.A.H., J.C.d.R., L.D.d.O. and C.A.T.C.; data curation, C.T.R., P.M.N.d.L., T.C.P., L.S.d.C., M.G.G.D., A.A.H., J.C.d.R., L.D.d.O. and C.A.T.C.; writing—original draft preparation, C.T.R., P.M.N.d.L., T.C.P., L.S.d.C., M.G.G.D. and J.C.d.R.; writing—review and editing, A.A.H., L.D.d.O. and C.A.T.C.; visualization, A.A.H., L.D.d.O. and C.A.T.C.; supervision, A.A.H., L.D.d.O. and C.A.T.C.; project administration, L.D.d.O. and C.A.T.C.; funding acquisition, L.D.d.O. and C.A.T.C. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

Data are available upon request (d.d.s.amjad@gmail.com).

Conflicts of Interest

The authors declare no conflicts of interest.

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Applsci 15 05534 g001
Figure 1. The microbial load (optical density) of the standard and clinical strains of E. faecalis and E. faecium biofilm after treatment with L. dentata essential oil for 30 min. Different lower-case letters (a, b and c) indicate a statistically significant difference among the experimental groups.
Figure 1. The microbial load (optical density) of the standard and clinical strains of E. faecalis and E. faecium biofilm after treatment with L. dentata essential oil for 30 min. Different lower-case letters (a, b and c) indicate a statistically significant difference among the experimental groups.
Applsci 15 05534 g001
Applsci 15 05534 g002
Figure 2. The microbial load (optical density) of the standard and clinical strains of E. faecalis and E. faecium biofilm after treatment with L. dentata essential oil for 24 h. Different lower-case letters (a, b and c) indicate a statistically significant difference among the experimental groups.
Figure 2. The microbial load (optical density) of the standard and clinical strains of E. faecalis and E. faecium biofilm after treatment with L. dentata essential oil for 24 h. Different lower-case letters (a, b and c) indicate a statistically significant difference among the experimental groups.
Applsci 15 05534 g002
Table 1. The antibiotic resistance of the clinical strains.
Table 1. The antibiotic resistance of the clinical strains.
Bacterial StrainACA + CEMAMTCCFVM
E. faecalis 1SSSSSSS
E. faecalis 2SSSSSIS
E. faecalis 3SSISRII
E. faecalis 4.1SSSSRSI
E. faecium 4.2SSIISSS
E. faecium 7.3SSSSSSS
Legend: S: sensitive, I: intermediate, R: resistant, AC: Amoxicillin, A + C: Amoxicillin/Clavulanic acid, EM: Erythromycin, AM: Azithromycin, TC: Tetracycline, CF: Ciprofloxacin, VM: Vancomycin.
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MDPI and ACS Style

Rocha, C.T.; de Lima, P.M.N.; Pereira, T.C.; de Carvalho, L.S.; Diamantino, M.G.G.; Abu Hasna, A.; da Rocha, J.C.; de Oliveira, L.D.; Carvalho, C.A.T. Antibacterial and Antibiofilm Effect of Lavandula dentata L. Essential Oil as Endodontic Irrigant Against Standard and Clinical Strains of Enterococcus spp. Appl. Sci. 2025, 15, 5534. https://doi.org/10.3390/app15105534

AMA Style

Rocha CT, de Lima PMN, Pereira TC, de Carvalho LS, Diamantino MGG, Abu Hasna A, da Rocha JC, de Oliveira LD, Carvalho CAT. Antibacterial and Antibiofilm Effect of Lavandula dentata L. Essential Oil as Endodontic Irrigant Against Standard and Clinical Strains of Enterococcus spp. Applied Sciences. 2025; 15(10):5534. https://doi.org/10.3390/app15105534

Chicago/Turabian Style

Rocha, Caroline Trefiglio, Patrícia Michelle Nagai de Lima, Thaís Cristine Pereira, Lara Steffany de Carvalho, Mariana Gadelho Gimenez Diamantino, Amjad Abu Hasna, João Carlos da Rocha, Luciane Dias de Oliveira, and Cláudio Antonio Talge Carvalho. 2025. "Antibacterial and Antibiofilm Effect of Lavandula dentata L. Essential Oil as Endodontic Irrigant Against Standard and Clinical Strains of Enterococcus spp." Applied Sciences 15, no. 10: 5534. https://doi.org/10.3390/app15105534

APA Style

Rocha, C. T., de Lima, P. M. N., Pereira, T. C., de Carvalho, L. S., Diamantino, M. G. G., Abu Hasna, A., da Rocha, J. C., de Oliveira, L. D., & Carvalho, C. A. T. (2025). Antibacterial and Antibiofilm Effect of Lavandula dentata L. Essential Oil as Endodontic Irrigant Against Standard and Clinical Strains of Enterococcus spp. Applied Sciences, 15(10), 5534. https://doi.org/10.3390/app15105534

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