From the point of view of remembering the scent of the essential oils, this study builds a volatilization characteristics map by considering vapor pressure. In this study, we developed a measuring system with two gas sensors to examine the volatilization characteristics of essential oils. The first and second gas sensors were set at distances of 15 and 30 mm, respectively, from the essential oil reservoir in the measuring tube. The measuring system was housed in a transparent case to eliminate the influence of external air fluctuations. A trial experiment was conducted for 60 s using Lavandula angustifolia to evaluate the measuring system. Three feature indicators were extracted: the upward gradient ratio of the first and second sensor signals, the maximum value of the first sensor signal, and the residual rate of the first sensor signal. We plotted a volatilization characteristics map with the upward gradient ratio of the first and second sensor signals on the horizontal axis and the maximum value of the first sensor signal on the vertical axis. Moreover, an advection–diffusion simulation was conducted to clarify the relationship between the volatilization characteristics map and the vapor pressure. The following conclusions were drawn from the simulation results: Advection–diffusion with a high velocity, that is, the essential oils with a high vapor pressure, were distributed on the upper side of the volatilization characteristics map. In contrast, the essential oils with a low vapor pressure were distributed on the lower side of the volatilization characteristics map. In addition, the gradient ratio of the first and second sensor signals changed with the vapor pressure and the content of the delayed scent that follows the initial scent. That is, a lower vapor pressure or a larger delayed scent content resulted in a more right-side in the volatilization characteristics map.

We attempted to generate a volatilization characteristics map for 17 essential oils in the Aromatherapy Proficiency Examination. The essential oils examined were Juniperus communis, Boswellia carterii, Rosmarinus officinalis, Eucalyptus globulus, Citrus limon, Citrus sinensis, Citrus paradisi, Melaleuca alternifolia, Origanum majorana, Anthemis nobilis, Pelargonium graveolens, Citrus bergamia, Lavandula angustifolia, Cymbopogon flexuosus, Salvia sclarea, Mentha piperita, and Cananga odorata. The volatilization characteristics were measured using a previously developed measuring system with the two gas sensors. The first and second gas sensors were placed at distances of 15 and 30 mm, respectively, from the essential oil reservoir in a measuring tube. Measurements were conducted for 3600 s for five samples of each of the 17 essential oils. Volatilization characteristics maps were plotted using three feature indicators: the maximum value of the first sensor signal, which is equivalent to the first scent (“First”); the gradient ratio of the first and second sensor signals, which is equivalent to the delayed scent (“Delay”); and the residual rate of the first sensor signal, which is equivalent to the lasting scent (“Lasting”). The following observations were made from two volatilization characteristics maps obtained with First–Delay and First–Lasting: In the First–Delay map, the high and low vapor pressures corresponded to the top and bottom of the map, respectively. In addition, a lower vapor pressure or a larger content of the delay scent resulted in a more right-side in the First–Delay map. Moreover, we reconfirmed the close similarity between the scents of Rosmarinus officinalis and Eucalyptus globulus based on measured data from the gas sensors and their relative positions in the First–Delay map. To summarize, the volatilization characteristics for the 17 essential oils in the Aromatherapy Proficiency Examination can be inferred from the First–Delay and First–Lasting maps.

[Introduction] Sleep bruxism causes various dental problems, consisting of tooth erosion, tooth and root fractures, temporomandibular joint disorder crisis, and tension headaches. Conversely, aromatherapy is highly relaxing and has recently been utilized in medical and nursing care settings. Dental treatment is frequently characterized by pain, dental phobia, etc., and aromatherapy remains unrecognized in the field of dentistry, where it is expected to exert a positive effect. Therefore, this study aimed to determine the effect and efficacy of essential oils in olfactory stimulation by investigating masseter muscle activity during sleep and propose a new treatment for sleep bruxism.

[Methods] The agents for aromatherapy included the essential oils of bergamot (Citrus bergamia) and marjoram (Organum majorana). Subsequently, we investigated the activity of the masseter muscle by measuring the rate-limiting masticatory muscle activity during the whole night’s sleep of 49 subjects. Measurements were conducted on day 2, without intervention as the baseline; day 3, with one essential oil; day 4, without intervention; day 5, with another essential oil; and day 6, without intervention. Measurements were then compared during the essential oil intervention with those of the baseline measurement on day 2. Moreover, the number of episodes per hour was compared among the groups.

[Results] The number of episodes was significantly decreased in marjoram relative to baseline (p=0.0346). The bergamot responder demonstrated a significantly reduced number of episodes for both essential oils. The marjoram responder exhibited a significant decrease in terms of the number of episodes and gender or preference. The number of episodes was significantly higher for both responders than for non-responders, indicating that those with sleep bruxism demonstrated both responses. Furthermore, the marjoram responder was more predominant in those with severe bruxism.

[Conclusions] Marjoram reduces sleep bruxism. Further, both marjoram and bergamot decreased sleep bruxism in patients with severe bruxism.

With the spread of coronavirus disease 2019 (COVID-19), the number of people working from home (WFH) had rapidly increased. To investigate the possibility of using essential oils as a mental and physical self-care method for individuals who WFH, we examined the effects of using essential oils on the mood, sleep quality, cognitive function, and work performance of these individuals. Twenty women and ten men who WFH (age: 25–49 years) participated in the present study. The participants used either rosemary or sweet orange during the daytime and either lavender or bergamot during the night, according to their preferences. The participants who inhaled essential oils 3 days a week or more for 4 weeks had significantly improved work performance, as assessed by using the Single-Item Presenteeism Question, as compared to the control group (p<0.05). Additionally, 10 minutes after smelling the essential oil selected according to their preferences, the vitality and stability levels and the degree of pleasure, determined by TDMS-ST, were significantly increased (p<0.05). In conclusion, our findings suggest that using essential oils could be a simple and useful method for improving mood and work performance of individuals who WFH.

The purity of commercial bergamot (Citrus bergamia Risso) essential oils was assessed by analyzing the enantiomers of linalool and linalyl acetate. The study included 34 cold-pressed oils and one steam-distilled oil obtained from peels. Additionally, laboratory-prepared samples comprised a cold-pressed oil and a hexane-extracted oil from bergamot fruit. The analysis also included three aged cold-pressed oils and a racemic reagent of linalool. The enantiomeric analysis was performed using gas chromatography-mass spectrometry with a chiral column in the selected-ion monitoring mode. The mass units were set at m/z 71.0, 93.0, 80.0 and 121.0 for linalool and linalyl acetate. Results demonstrated that the enantiomer excess % of (R)-(−)-linalool over (S)-(+)-linalool exceeded 98.0% in most commercial cold-pressed and steam-distilled bergamot oils, as well as in the lab-prepared and aged samples. These findings indicate that the enantiomeric composition was unaffected by the experimental conditions. In conclusion, based on the enantiomeric excess of (R)-(−)-linalool, the high enantiomeric purity of 29 of commercial bergamot essential oils was confirmed, while the remaining 9 oils did not meet the verification criteria.