Oral malodor still constitutes a major challenge worldwide. A strong effort is invested in eliminating volatile sulfur compound-producing oral bacteria through organic natural products such as essential oils. Fusobacterium nucleatum is a known volatile sulfur compound-producing bacteria that inspires oral malodor. The aim of the present study was to test the effect of lavender essential oil on the bacterium’s ability to produce volatile sulfide compounds, the principal components of oral malodor. Lavender (Lavandula angustifolia) essential oil was extracted by hydrodistillation and analyzed using GC-MS. The minimal inhibitory concentration (MIC) of lavender essential oil on Fusobacterium nucleatum was determined in a previous trial. Fusobacterium nucleatum was incubated anaerobically in the presence of sub-MIC, MIC, and above MIC concentrations of lavender essential oil, as well as saline and chlorhexidine as negative and positive controls, respectively. Following incubation, volatile sulfur compound levels were measured using GC (Oralchroma), and bacterial cell membrane damage was studied using fluorescence microscopy. Chemical analysis of lavender essential oil yielded five main components, with camphor being the most abundant, accounting for nearly one-third of the total lavender essential oil volume. The MIC (4 µL/mL) of lavender essential oil reduced volatile sulfur compound secretion at a statistically significant level compared to the control (saline). Furthermore, the level of volatile sulfur compound production attributed to 1 MIC of lavender essential oil was in the range of the positive control chlorhexidine with no significant difference. When examining bacterial membrane damage, 2 MIC of lavender essential oil (i.e., 8 µL/mL) demonstrated the same, showing antibacterial membrane damage values comparative to chlorhexidine. Since lavender essential oil was found to be highly effective in hindering volatile sulfur compound production by Fusobacterium nucleatum through the induction of bacterial cell membrane damage, the results suggest that lavender essential oil may be a suitable alternative to conventional chemical-based anti-malodor agents.

Streptococcus mutans is considered a major cariogenic bacterium. Most anti-cariogenic dentifrices are limited by a short exposure time. The aim of the present study was to test the hypothesis that adding a mucoadhesive agent to the formulation may increase its bioavailability and efficacy. We tested the effect of adding hydroxyethyl cellulose (HEC) to an herbal extract solution containing lavender, echinacea, sage, and mastic gum, which have been previously shown to be effective against Streptococcus mutans. Mucin-coated wells were treated with four test solutions: saline, herbal extracts, herbal extracts with HEC, and chlorhexidine. The wells were incubated with Streptococcus mutans and studied for biofilm formation (Crystal violet assay), acid production (lactate assay), acid tolerance (ATPase assay), and exopolysaccharide (EPS) production using fluorescent microscopy. The results showed that the addition of HEC to the herbal extract solution caused a significant reduction in Streptococcus mutans biofilm formation, lactic acid production, and EPS quantity (p < 0.001). These results suggest that HEC may be a beneficial added excipient to herbal extracts in an anti-cariogenic formulation.

A previous study showed that sub-lethal exposure of blue light caused cell membrane damage in Fusobacterium nucleatum (Fn). The aim of the present study was to test the combined effect of blue light and silver nanoparticles against Fn. Bacterial suspensions were exposed to blue light (400–500 nm) with or without silver nanoparticles (10 nm). Exposed and non-exposed samples were studied for malodor production (Odor judge scores), VSC levels (Halimeter), reactive oxygen species (ROS) production (fluorimeter), and bacterial cell membrane damage (fluorescence microscopy). The results showed that combining blue light exposure and silver nanoparticles significantly reduced malodor and VSC production by Fn concomitant with increased ROS levels and bacterial cell membrane damage. These results suggest that silver nanoparticles may increase blue light phototoxicity against Fn.

Temporary dental crowns and bridges are commonly made of poly-methylmethacrylate (PMMA), a porous material attracting the microbial biofilm associated with malodor production. The purpose of the present study was to test pre-disinfection of PMMA on malodor-related parameters in an experimental oral biofilm. PMMA discs were pre-soaked in anti-malodor disinfecting solutions and controls: (i) Saline, (ii) essential oils (EO), (iii) herbal extracts (HE), and (iv) chlorhexidine (CHX). Following, discs were subjected to a salivary incubation assay and monitored for malodor-producing bacteria within the biofilm using confocal microscopy (CLSM), malodor production (organoleptic scale 0–5), volatile sulfide levels (Halimeter), and salivary protein degradation (SDS-PAGE). Results showed that disinfection solutions were significantly effective in reducing malodor-related parameters (CHX > HE > EO > Saline). Taken together, these results suggest that pre-disinfection may help to reduce malodor production in PMMA temporary dental restorations.

Coaggregation by bridging bacteria such as Fusobacterium nucleatum is considered a key element in dental biofilm development and maturation. Previous studies showed that sublethal exposure to blue light caused damage to cell membrane integrity. The aim of the present study was to test the effect of blue light phototoxicity on this bacterium’s ability to coaggregate with the early colonizer Streptococcus sanguinis. Fusobacterium nucleatum bacterial cells were suspended in coaggregation buffer (CAB) and exposed to blue light (400–500 nm) for 0, 70, 140 and 280 s (i.e., fluences of 0, 96, 192 and 384 J/cm², respectively). Following blue light exposure, samples were mixed with Streptococcus sanguinis suspensions and coaggregation was measured using a visual scale, spectrophotometric analysis and light microscopy. Results showed that blue light exposure significantly reduced the ability of Fusobacterium nucleatum to coaggregate with Streptococcus sanguinis. These results suggest that blue light antibacterial phototoxicity may be considered as a viable option in preventing dental biofilm-related conditions.

Previous studies have shown that sub-lethal exposure of blue light caused increased bacterial cell membrane permeability. We hypothesized that combining blue light exposure with other antibacterial agents may increase their efficacy. The aim of the present study was to test the combined effect of blue light and sodium fluoride against dental caries pathogen Streptococcus mutans. Sm biofilms were exposed to blue light (400–500 nm) with or without sodium fluoride. Exposed and non-exposed samples were studied for acid production (lactate assay kit), acid tolerance (ATPase assay kit) and bacterial cell membrane damage (fluorescence microscopy). Results showed that the combined treatment significantly reduced the virulence of Sm concomitant with an increase in bacterial cell membrane permeability. Taken together, these results suggest that adjacent blue light exposure may increase fluoride caries preventive properties.