Antiplaque effect of essential oils and 0.2% chlorhexidine on an in situ model of oral biofilm growth: a randomised clinical trial

Abstract

Objective: To evaluate the in situ antiplaque effect after 4 days of using of 2 commercial antimicrobial agents in short term on undisturbed plaque-like biofilm.

Trial design and participants: An observer-masked, crossover randomised clinical trial on 15 oral and systemically healthy volunteers between 20-30 years who were randomly and sequentially allocated in the same group which performed 3 interventions in different randomised sequences.

Intervention: The participants wore an appliance in 3 different rinsing periods doing mouthwashes twice a day (1/0/1) with essential oils, 0.2% chlorhexidine or sterile water (negative control). At the end of each 4-day mouthwash period, samples were removed from the appliance. Posteriorly, after bacterial vital staining, samples were analysed using a Confocal Laser Scanning Microscope.

Main outcome measures: Bacterial vitality, thickness and covering grade by the biofilm after 4 days of applying each of the mouthwashes.

Results: The essential oils and the 0.2% chlorhexidine were significantly more effective than the sterile water at reducing bacterial vitality, thickness and covering grade by the biofilm. No significant differences were found between the 0.2% chlorhexidine and the essential oils at reducing the bacterial vitality (13.2% vs. 14.7%). However, the 0.2% chlorhexidine showed more reduction than the essential oils in thickness (6.5 μm vs. 10.0 μm; p<0.05) and covering grade by the biofilm (20.0% vs. 54.3%; p<0.001).

Conclusion: The essential oils and 0.2% chlorhexidine showed a high antiplaque effect. Although the 0.2% chlorhexidine showed better results with regard to reducing the thickness and covering grade by the biofilm, both antiseptics showed a high and similar antibacterial activity.

Clinical relevance: Daily essential oils or 0.2% chlorhexidine mouthwashes are effective when reducing dental plaque formation in the short term. Although 0.2% chlorhexidine continues to be the "gold standard" in terms of antiplaque effect, essential oils could be considered a reliable alternative.

Trial registration: ClinicalTrials.gov NCT02124655.

Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Fig 1. Flow diagram of the study with enrollment, allocation, follow-up and analysis of participants.

Fig 2. Scheme of the sequence of protocols followed by the volunteers.

Fig 3. Scheme of the divisions of the PL-Biofilm in layers.

1-Outer layer; 2-Middle layer; 3-Inner layer. *PL-Biofilm. **Glass disk (substrate).

Fig 4. On the left, lateral projections of the brightest point (X-Z) from images stacked in Y plane from the three rinsing cycles, presenting their respective mean thickness.

On the right, maximum projections of the brightest point (X-Y) from images stacked in Z plane. 4D-WATER = 4-day period during which rinses with 20 mL of sterile water are done twice a day; 4D-EO = 4-day period during which rinses with 20 mL of essential oils are done twice a day; 4D-0.2% CHX = 4-day period during which rinses with 10 mL of 0.2% chlorhexidine are done twice a day.

Fig 5. Bacterial vitality in percentages.

Total and different layers in each rinsing cycle. 4D-WATER = 4-day period during which rinses with 20 mL of sterile water are done twice a day; 4D-EO = 4-day period during which rinses with 20 mL of essential oils are done twice a day; 4D-0.2% CHX = 4-day period during which rinses with 10 mL of 0.2% chlorhexidine are done twice a day. Layer 1 = outer layer; Layer 2 = middle layer; Layer 3 = inner layer.

Fig 6. Scheme of the area occupied by the PL-Biofilm after the different rinsing cycles.

Presentation of the obtained cyphers. 4D-WATER = 4-day period during which rinses with 20 mL of sterile water are done twice a day; 4D-EO = 4-day period during which rinses with 20 mL of essential oils are done twice a day; 4D-0.2% CHX = 4-day period during which rinses with 10 mL of 0.2% chlorhexidine are done twice a day.