Periodontitis is associated with impaired olfactory function: A clinical study

AIM

To explore the association between periodontitis and olfactory disorders.

METHODS

Clinical data were collected from 198 individuals between the ages of 18 and 60 years living in Denmark. The exposure was periodontitis, and the outcome was olfactory function (Threshold, Discrimination, Identification - TDI score), both measured clinically. Covariates included sex, age, education level, income, usage of nasal spray, tongue coating, halitosis, xerostomia, smoking, and history of COVID-19. Structural equation modeling was used to estimate the association between periodontitis and olfactory function. Periodontitis was defined using the AAP/EFP classification and dichotomized into "no" (healthy subjects) and "yes" (Stages I, II, and III). Olfactory function was treated as a one-factor latent variable, including the different olfactory scores. In addition, extra models were performed considering each olfactory component as a separate outcome and the TDI Global Score.

RESULTS

The results showed that periodontitis was associated with a lower olfactory function [standardized coefficient (SC) -0.264, 95% CI -0.401, -0.118]. Additionally, periodontitis was also associated with a lower olfactory Threshold (odorant concentration required for detection) (SC -0.207, 95% CI -0.325, -0.089), Discrimination (ability to discriminate between odorants) (SC -0.149, 95% CI -0.270, -0.027), Identification (ability to identify odorants) scores (SC -0.161, 95% CI -0.277, -0.045), and TDI Global Score (SC -0.234, 95% CI -0.370, -0.099).

CONCLUSIONS

This study suggests that periodontitis is associated with olfactory impairment.

Self-reported periodontitis association with impaired smell and taste: A multicenter survey

OBJECTIVES

To investigate the association between self-reported periodontitis and the senses of taste and smell among employees of one Danish and two American universities.

MATERIALS AND METHODS

Data were collected through a digital survey. A total of 1239 individuals from Aarhus University - Denmark, the University of Iowa, and the University of Florida - USA were included. Self-reported periodontitis was the exposure. The perceived senses of taste and smell were the outcomes and were measured through a visual analog scale (VAS). Self-perceived halitosis was the mediator. Confounders were age, sex, income, education, xerostomia, COVID-19, smoking, body mass index, and diabetes. The total effect was decomposed into direct and indirect using a counterfactual approach.

RESULTS

The total effect of periodontitis on an impaired sense of taste was OR 1.56 (95% CI [1.02, 2.09]), of which 23% was mediated by halitosis (OR 1.13; 95% CI [1.03, 1.22]). Additionally, individuals with self-reported periodontitis had a 53% higher chance of having impaired smell (OR 1.53; 95% CI [1.00, 2.04]), with halitosis mediating 21% of the total effect (OR 1.11; 95% CI [1.02, 1.20]).

CONCLUSION

Our findings suggest that periodontitis is associated with distorted senses of taste and smell. Additionally, this association appears to be mediated by halitosis.

Smellscape as a healing factor in institutional gardens to enhance health and well-being for older people with dementia: A scoping review

BACKGROUND

There is mounting evidence for the health benefits of aromatic scents for the older people with dementia. However, existing research has focused on indoor aromatherapy using essential oils. It is necessary to explore the health benefits of smellscapes in the outdoor environment for older people with dementia.

AIMS AND OBJECTIVES

This scoping review aims to examine existing evidence for smellscape as a healing factor in institutional garden for older people with dementia, try to bridge the knowledge gaps between outdoor sensory garden scents and aromatherapy to develop green care techniques that incorporate outdoor activities.

METHODS

Seven databases (Scopus, PubMed, PsycINFO, CINAHL, MEDLINE, Embase and Web of Science) were searched with English language articles published between 1990 and 2022. The PRISMA-ScR Checklist was used.

RESULTS

Out of 1013 articles, 11 meet the inclusion criteria. The comprehensive health outcomes include five aspects: mental health; physical health; reduced agitation behaviour; improved cognitive function; and well-being. These aspects are part of the rehabilitation model comprising the person (older people with dementia), environment (garden smellscapes) and outdoor activities (active or passive interventions or a combination).

CONCLUSIONS

The smellscape, as a healing factor in the garden, not only benefits from evidence on indoor aromatherapy but also creates a sensory environment for older people with dementia by compensating for functional impairment, activity support and environmental creation, thereby promoting enhanced health and well-being.

RELEVANCE TO CLINICAL PRACTICE

The research on the healing effects of smellscapes presented in this review offers a novel environmental intervention technique for transferring evidence on essential oils to outdoor sensory gardens. This green care technique is suggested to assist in the creation of healing environments and interventions for people with dementia who cannot be cured.

NO PATIENT OR PUBLIC CONTRIBUTION

This scoping review did not directly involve patient or public contributions to the manuscript.

The impact of wearing powered air purifying respirators or N95 masks on the olfactory function in healthcare workers: A randomized controlled trial

BACKGROUND

With the Coronavirus disease 2019 epidemic, wearing a mask has become routine to prevent and control the virus's spread, especially for healthcare workers. However, the impact of long-term mask wear on the human body has not been adequately investigated. This study aimed to investigate whether Powered Air Purifying Respirators and N95 masks impact the olfaction in healthcare workers.

METHODS

We recruited fifty-six healthcare workers and randomly divided them into 2 groups, wearing a powered air purifying respirator (PAPR) (experiment group, N = 28) and an N95 mask (control group, N = 28). Olfactory discrimination and threshold tests were performed before and after wearing the masks. SPSS 26.0 (SPSS Inc., Chicago, Illinois) software was used for the statistical analyses.

RESULTS

There was a statistical difference in the olfactory threshold test after wearing the mask in both PAPR Group (Z = -2.595, P = .009) and N95 Group (Z = -2.120, P = .034), with no significant difference between the 2 (χ2 = 0.29, P = .589). There was no statistical difference in the discrimination test scores in both 2 groups after wearing the masks.

CONCLUSION

Wearing a mask affects the healthcare workers' olfaction, especially odor sensitivity. Healthcare workers have a higher olfactory threshold after long-term mask wear, whether wearing PAPRs or N95 masks.

The influence of opioid blockage on the sexual response cycle: A randomized placebo-controlled experiment with relevance for the treatment of Compulsive Sexual Behavior Disorder (CSBD)

The use of opioid antagonists is discussed as a feasible and tolerable treatment of Compulsive Sexual Behavior Disorder (CSBD). However, little is known about the influence of opioid blockage on relevant physiological functions such as sexual arousal, pain perception as well as disgust sensitivity during the sexual response cycle (SRC). Healthy participants (N = 64, n = 32 women) were invited to the laboratory twice using a double-blind, randomized cross-over design, with an interval of four weeks between sessions. Participants were randomly subjected to an SRC condition (including an erotic audio play and masturbation to orgasm) and a control condition. Participants received either naltrexone (50 mg, n = 32) or placebo at both sessions. Self-reported sexual arousal and physiological measures of arousal as well as pain perception, odor disgust sensitivity, and prolactin levels were assessed along the SRC. Naltrexone increased prolactin levels and blunted the orgasm-induced prolactin rise. Naltrexone also reduced self-reported sexual arousal throughout the sexual response cycle and blunted respiration rate during masturbation. However, naltrexone did not affect other markers of physiological arousal, pressure pain ratings and odor disgust sensitivity. These findings suggest that naltrexone has an acute negative effect on sexual arousal. Since prolactin levels mediate sexual satiation, we propose that a prolactin-induced increase in sexual satiation could explain the positive effects reported for naltrexone in the treatment of CSBD.

Something Stinks! Finding Ways to Manage Noxious Odours in the Operating Room and Other Clinical Settings A Randomized Controlled Trial

Objectives: The hospital can be saturated with noxious smells. Anecdotally, medical staff apply products to surgical masks to lessen the impact of these smells. This study aimed to determine the odour-masking ability of 4 inexpensive and convenient products. Methods: A randomized, single-blinded crossover study was conducted in Vancouver, Canada. Participants, 19 to 30 years old, were invited to participate. Participants with active allergies, upper respiratory tract infection, alteration to sense of smell, or failure of olfactory screen were excluded from the study. An experimental odour was used in lieu of a noxious surgical odour. After smelling the experimental odour without barriers, participants were re-exposed to the odour using 5 surgical masks in randomized order. Each mask was lined with a test product (cherry lip balm, tincture of benzoin, Mastisol, mint toothpaste, and control [plain mask]). Participants rated the effectiveness of products at masking the experimental odour from 0 to 100 (0 = completely ineffective, 100 = completely effective). Participants also rated the pleasantness of the products, recorded if the products made them feel unwell, and identified their preferred product overall. Results: Eighty participants were included in the study (33 male, 47 female), averaging 24.2 years of age. Mean odour-masking effectiveness for cherry lip balm was 66.5 (±24.6), tincture of benzoin: 62.6 (±25.0), Mastisol: 61.3 (±23.9), mint toothpaste: 57.5 (±27.4), and control: 21.9 (±21.8). All products performed better than the control (P < .001), but there was no significant difference in performance between products. Cherry lip balm was the most preferred odour-masking product (29 participants), followed by mint toothpaste (22), Mastisol (14), tincture of benzoin (10), and control (5). Conclusions: All tested products demonstrated equivalent odour-masking abilities. If health care professionals choose to use an odour-masking product, they should consider their own olfactory preferences.

Olfactory stimulation for people with dementia: A rapid review

There is a growing interest in using olfactory (smell) stimulation in dementia care. This study aims to extend current knowledge by synthesising the evidence on the efficacy of interventions using olfactory stimulation for people with dementia and to assess the effects of different types of odours and administration methods using a mixed methods approach. The rapid review was conducted based on searches in six electronic databases. A narrative approach was applied to assess 20 studies included in the review. Fourteen studies used a quasi-experimental design, five studies used an experimental design and one was a case study. High heterogeneity was found on odours and methods of application used, with the majority of studies administering lavender oil using a diffuser. Mixed results were reported on the benefits of olfactory stimulation on responsive behaviours and cognitive function. Although the evidence available is limited, encouraging results were found regarding olfactory stimulation and increased sleep duration, food intake and improved balance. It was not possible to draw any overall conclusion in relation to the effect of olfactory stimulation. However, this review shows promising results that support further investigation of olfactory stimulation as a nonpharmacological intervention for people with dementia. The review is limited due to the low to moderate quality of studies included. Furthermore, the broad range of approaches was employed, and comparison between the studies was difficult. Further high-quality mixed method studies using robust and detailed protocols are needed to clarify the effects of olfactory stimuli and any other factors that may influence the responses of people with dementia.

Olfactory adaptation: recordings from the human olfactory epithelium

Purpose

Olfactory adaptation is a peripheral (at the epithelium level) or a central (at the brain level) mechanism resulting from repeated or prolonged odorous exposure that can induce a perceptual decrease. The aim of this study was to assess whether a peripheral adaptation occurs when an odor is repeated ten times. Moreover, the specificity of the peripheral adaptation to the nature of the odorant was investigated.

Methods

Four odorants (eugenol, manzanate, ISO E Super and phenylethanol) were presented using precisely controlled air-dilution olfactometry. They differed in terms of their physicochemical properties. Electrophysiological recordings were made at the level of the olfactory mucosa, the so-called electro-olfactogram (EOG). Thirty-five right-handed participants were recruited.

Results

Sixty-nine percent of the participants presented at least one EOG, whatever the odor condition. The EOG amplitude did not significantly decrease over 10 repeated exposures to any odorant. The intensity ratings tended to decrease over stimulations for manzanate, PEA, and eugenol. No correlation was found between the mean EOG amplitudes and the mean intensity ratings. However, the presence of EOG amplitude decreases over stimulations for few subjects suggests that peripheral adaptation might exist.

Conclusion

Overall, our results did not establish a clear peripheral adaptation measured with EOG but indicate the eventuality of such an effect.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00405-021-07170-0.

Effect of fixed orthodontic appliances on self-assessment and diagnosis of halitosis in undergraduate dental students

Background:

The effects of fixed orthodontic therapy on the occurrence of halitosis are not yet fully understood. This study aimed to evaluate the effect of fixed orthodontic appliances on self-assessment and diagnosis of halitosis in undergraduate dental students.

Materials and Methods:

Sixty-two undergraduate dental students were included in this cross-sectional study. Two groups (n = 31 per group) were composed of participants with (study group) or without (control group) fixed orthodontic appliance. Halitosis self-assessment and clinical diagnosis were assessed using a visual analogic scale (VAS) and sulfur volatile compounds (SVCs) assessment, respectively. The subjective (VAS) and objective (SVC) malodor assessments were classified in absence, light, moderate, or severe malodor. Chi-square Pearson test and Spearman's correlation were applied for data analysis, with a significance level of 5%.

Results:

The use of fixed orthodontic appliances had no effect on self-assessment (P = 0.490) or clinical diagnosis (P = 0.610) of halitosis. Self-assessment was not significantly associated with the diagnosis of halitosis regardless the use of fixed orthodontic appliance (P ≥ 0.737). Male participants showed higher diagnosis of halitosis (P = 0.007). SVC measurements showed the absence of halitosis in 51.6% and 58.1% of participants with or without orthodontic appliances, respectively.

Conclusion:

The use of fixed orthodontic appliances affected the self-assessment of halitosis but no SVC measurements. It was not verified a correlation between subjective and objective methods to diagnose halitosis in dental students.

Olfactory Virtual Reality: A New Frontier in the Treatment and Prevention of Posttraumatic Stress Disorder

This perspective piece reviews the clinical condition of posttraumatic stress disorder (PTSD), which is currently increasing due to the COVID-19 pandemic, and recent research illustrating how olfaction is being incorporated into virtual reality (VR) platforms. I then discuss the latest work examining the potential of olfactory virtual reality (OVR) for the treatment of PTSD. From this foundation I suggest novel ways in which OVR may be implemented in PTSD therapy and harnessed for preventing the development of PTSD. Perceptual and chemical features of olfaction that should be considered in OVR applications are also discussed.

Olfaction in patients with Parkinson's disease: a new threshold test analysis through turning points trajectories

Olfactory deficit is a widely documented non-motor symptom in Parkinson’s disease (PD). Abnormal turning points trajectories through olfactory threshold testing have been recently reported in patients with olfactory dysfunction, who seem to adapt faster to olfactory stimuli, but data on PD patients are lacking. The aim of this study is to perform olfactory threshold test and explore the turning points trajectories in PD patients in comparison to normal controls. We recruited 59 PD patients without dementia, and no conditions that could influence evaluation of olfaction and cognition. Sixty healthy subjects served as controls. Patients and controls underwent a comprehensive olfactory evaluation with the Sniffin’ Sticks extended test assessing threshold, discrimination and identification and a full neuropsychological evaluation. Besides, threshold test data were analyzed examining all the turning points trajectories. PD patients showed a different olfactory threshold test pattern, i.e., faster olfactory adaptation, than controls with no effect of age. Normosmic PD patients showed different olfactory threshold test pattern, i.e., better threshold score, than normosmic controls. Visuospatial dysfunction was the only factor that significantly influenced this pattern. Olfactory threshold trajectories suggested a possible adaptation phenomenon in PD patients. Our data offered some new insights on normosmic PD patients, which appear to be a subset with a specific psychophysical profile. The analysis of the turning points trajectories, through an olfactory threshold test, could offer additional information on olfactory function in PD patients. Future larger studies should confirm these preliminary findings.

Could Self-Consciousness Be Enhanced in Alzheimer’s Disease? An Approach from Emotional Sensorial Stimulation

Alzheimer’s disease (AD) provides a valuable field of research into impairment of self-consciousness (SC), because AD patients have a reduced capacity to understand their mental world, to experience and relive previous personal events, as well as to interpret thoughts, feelings, and beliefs about themselves. Several studies observed that AD patients had an altered SC, but not a complete abolition of it. Emotions are an integral part of the construction of personal identity, therefore of Self. In general, most studies on emotion in AD patients have observed that emotion is not completely abolished and it lets them better remember autobiographical events with greater emotional charge. The positive effect of autobiographical memories rich in emotional content, evoked directly/automatically by sensorial stimuli such as familiar odors or music, could be used to reestablish/reinforce the permanence and coherence of the Self in AD. We studied the research of empirical evidence supporting the power of the sensorial cues associated with emotion, which could be capable of enhancing the SC in AD. We presented the studies about “Emotional stimulations” using odor, music, or taste cues in AD. All studies have shown to have a positive impact on SC in AD patients such as odor-evoked autobiographical memories, taste/odor-evoked autobiographical memories, emotional sensorial stimulation using musical cues, and multi-sensorial stimulations using healing gardens. We found research supporting the notion that emotional sensorial stimulations can even temporarily exalt memory, affective state, and personal identity, that is, the SC in AD. The emotional sensory stimulations could be used as a tool to activate the SC in AD and hence improve the quality of life of patients and caregivers.

Development of a "Turn-on" Fluorescent Probe-Based Sensing System for Hydrogen Sulfide in Liquid and Gas Phase

A “turn-on” fluorescence sensing system based on a BODIPY-cobaloxime complex for the detection of H₂S in liquid and gas phase was developed. To that aim, two cobaloxime complexes bearing an axial pyridyl-BODIPY ligand were initially evaluated as sensitive fluorescent HS⁻ indicators in aqueous solution. The sensing mechanism involves the selective substitution of the BODIPY ligand by the HS⁻ anion at the cobalt center, which is accompanied by a strong fluorescence enhancement. The selection of a complex with an ideal stability and reactivity profile toward HS⁻ relied on the optimal interaction between the cobalt metal-center and two different pyridyl BODIPY ligands. Loading the best performing BODIPY-cobaloxime complex onto a polymeric hydrogel membrane allowed us to study the selectivity of the probe for HS⁻ against different anions and cysteine. Successful detection of H₂S by the fluorescent “light-up” membrane was not only accomplished for surface water but could also be demonstrated for relevant H₂S concentrations in gas phase.

Attentional modulation of desensitization to odor

Subjective and behavioral responsiveness to odor diminishes during prolonged exposure. The precise mechanisms underlying olfactory desensitization are not fully understood, but previous studies indicate that the phenomenon may be modulated by central-cognitive processes. The present study investigated the effect of attention on perceived intensity during exposure to a pleasant odor. A within-subjects design was utilized with 19 participants attending 2 sessions. During each session, participants continuously rated their perceived intensity of a 10-minute exposure to a pleasant fragrance administered using an olfactometer. An auditory oddball task was implemented to manipulate the focus of attention in each session. Participants were instructed to either direct their attention toward the sounds, but still to rate odor, or to focus entirely on rating the odor. Analysis revealed three 50-second time windows with significantly lower mean intensity ratings during the distraction condition. Curve fitting of the data disclosed a linear function of desensitization in the focused attention condition compared with an exponential decay function during distraction condition, indicating an increased rate of initial desensitization when attention is distracted away from the odor. In the focused-attention condition, perceived intensity demonstrated a regular pattern of odor sensitivity occurring at approximately 1−2 minutes intervals following initial desensitization. Spectral analysis of low-frequency oscillations confirmed the presence of augmented spectral power in this frequency range during focused relative to distracted conditions. The findings demonstrate for the first time modulation of odor desensitization specifically by attentional factors, exemplifying the relevance of top-down control for ongoing perception of odor.

CD36 involvement in the olfactory perception of oleic aldehyde, an odour-active volatile compound, in mice

Cluster of differentiation 36 (CD36) is a broadly expressed transmembrane receptor that has multiple ligands. It has been found to occur abundantly on the surface of the olfactory epithelium in mice and postulated to play a role in mammalian olfaction. However, there have been no ethological analyses of the mammalian behaviour showing CD36 involvement in the olfactory perception of a distinct odour-active volatile compound. In this study, we aimed to assess whether mammals perceive oleic aldehyde, an odour-active volatile that serves as a potential CD36 ligand, and if so, whether CD36 is involved in the sensing by following measurements using CD36-knockout mice and their wild-type littermates. In a two-bottle choice test, wild-type mice, but not CD36-knockout mice, discriminated a sucrose solution containing oleic aldehyde from the sucrose solution alone. To assess the importance of the olfactory system in the oleic aldehyde perception, we conducted an exploration test where the animals could rely primarily on the odour of test volatiles for recognition. We found that the wild-type, but not CD36-knockout mice, were aware of the compound. Our results provide behavioural evidence that CD36 plays a role in the perception of specific odour-active volatile compounds in the nasal cavity.

The Presentation of Olfactory-Trigeminal Mixed Stimuli Increases the Response to Subsequent Olfactory Stimuli

The aim of this study was to evaluate the effect of (1) the addition of trigeminal stimuli to an olfactory stimulus and (2) the congruence in the odorous mixture after repeated odor presentation. Twenty-five normosmic volunteers were enrolled and presented stimulation blocks, consisting of three habituation stimuli (H) (orange odor), one dishabituation (DH) (control condition, orange odor; congruent condition, orange odor + CO₂; incongruent condition, orange odor + l-isopulegol), and one dishabituated stimulus (D) (orange odor). Olfactory event-related potentials were analyzed. Response amplitudes differed significantly in the incongruent condition (N1P2 between H3 and D; peak to peak N1P2 at electrode positions Cz, Fz, and Pz; response amplitudes between H3 and DH). The addition of CO₂ modified the perception of orange odor, pronouncing a fruity note, whereas the addition of l-isopulegol as a DH pronounced the l-isopulegol note. This study provides evidence that incongruent trigeminal-olfactory stimulants increase the response to subsequent olfactory stimulus.

Causality Assessment of Olfactory and Gustatory Dysfunction Associated with Intranasal Fluticasone Propionate: Application of the Bradford Hill Criteria

Causality assessment is crucial to post-marketing pharmacovigilance and helps optimize safe and appropriate use of medicines by patients in the real world. Self-reported olfactory and gustatory dysfunction are common in the general population as well as in patients with allergic rhinitis and nasal polyposis. Intranasal corticosteroids, including intranasal fluticasone propionate (INFP), are amongst the most effective drugs indicated in the treatment of allergic rhinitis and nasal polyposis. While intranasal corticosteroids are associated with olfactory and gustatory dysfunction and are currently labeled for these adverse events, causality assessment has not been performed to date. Although there is no single widely accepted method to assess causality in pharmacovigilance, the Bradford Hill criteria offer a robust and comprehensive approach because nine distinct aspects of an observed potential drug–event association are assessed. In this literature-based narrative review, Hill’s criteria were applied to determine causal inference between INFP and olfactory and gustatory dysfunction.

Fat Sensation: Fatty Acid Taste and Olfaction Sensitivity and the Link with Disinhibited Eating Behaviour

Perception of fat taste, aroma, and texture are proposed to influence food preferences, thus shaping dietary intake and eating behaviour and consequently long-term health. In this study, we investigated associations between fatty acid taste, olfaction, mouthfeel of fat, dietary intake, eating behaviour, and body mass index (BMI). Fifty women attended three sessions to assess oleic acid taste and olfaction thresholds, the olfactory threshold for n-butanol and subjective mouthfeel ratings of custard samples. Dietary intake and eating behaviour were evaluated using a Food Frequency and Three-Factor Eating Questionnaire, respectively. Binomial regression analysis was used to model fat taste and olfaction data. Taste and olfactory detection for oleic acid were positively correlated (r = 0.325; p < 0.02). Oleic acid taste hypersensitive women had significantly increased n-butanol olfactory sensitivity (p < 0.03). The eating behaviour disinhibition and BMI were higher in women who were hyposensitive to oleic acid taste (p < 0.05). Dietary intake of nuts, nut spreads, and seeds were significantly correlated with high olfactory sensitivity to oleic acid (p < 0.01). These findings demonstrate a clear link between fatty acid taste sensitivity and olfaction and suggest that fat taste perception is associated with specific characteristics of eating behaviour and body composition.

Habituation and adaptation to odors in humans

Habituation, or decreased behavioral response, to odors is created by repeated exposure and several detailed characteristics, whereas adaptation relates to the neural processes that constitute this decrease in a behavioral response. As with all senses, the olfactory system continually encounters an enormous variety of odorants which is why mechanisms must exist to segment them and respond to changes. Although most olfactory habitation studies have focused on animal models, this non-systematic review provides an overview of olfactory habituation and adaptation in humans, and techniques that have been used to measure them. Thus far, psychophysics in combination with modern techniques of neural measurement indicate that habituation to odors, or decrease of intensity, is relatively fast with adaptation occurring more quickly at higher cerebral processes than peripheral adaptation. Similarly, it has been demonstrated that many of the characteristics of habitation apply to human olfaction; yet, evidence for some characteristics such as potentiation of habituation or habituation of dishabituation need more support. Additionally, standard experimental designs should be used to minimize variance across studies, and more research is needed to define peripheral-cerebral feedback loops involved in decreased responsiveness to environmental stimuli.

Halitosis Assessment and Changes in Volatile Sulfur Compounds After Chewing Gum: A Study Performed on Dentistry Students

OBJECTIVE

The objective of this study is to estimate the prevalence of halitosis (with subjective and objective methods), evaluate the immediate effect of chewing gum on volatile sulfur compounds (VSCs), assess the perception of halitosis by dentistry students, and estimate the distribution of positive and negative frequencies, when comparing objective and subjective methods for the diagnosis of halitosis.

METHODS

The study was performed on a sample of dentistry students attending the Faculty of Medicine and Health Sciences at the University of Barcelona. A questionnaire about halitosis perception was provided and a clinical examination, organoleptic test (OT), and gas chromatography were performed to determine the presence of halitosis. The subjects were also given chewing gum to modify their breath, and gas chromatography was carried out to evaluate possible changes in VSCs.

RESULTS

The sample comprised 80 individuals. Twenty-seven (33.75%) self-perceived halitosis during the period of evaluation; the OT was positive in 38 subjects (47.5%); and individuals positive for halitosis on gas chromatography were distributed as follows: H₂S in 25 (31.25%), CH₃SH in 28 (35%), and (CH₃)₂S in 70 individuals (87.5%). A statistical difference before and after chewing gum (P < .05) was found for each VSC; a difference in frequencies was observed between the variable OT and H₂S (P < .05) and between the OT and (CH₃)₂S (P < .001). There was no significant difference (P > .05) between the positive and negative frequencies retrieved between the variable OT and CH₃SH and between the OT and the student's halitosis perception.

CONCLUSION

Prevalence of halitosis in the studied sample is high, considering that it comprised healthy individuals. The relationship between the OT and gas chromatography is not completely established. Chewing gum could be considered a therapeutic alternative to decrease or neutralize the amount of VSCs present in oral breath.

New determinants of olfactory habituation

Habituation is a filter that optimizes the processing of information by our brain in all sensory modalities. It results in an unconscious reduced responsiveness to continuous or repetitive stimulation. In olfaction, the main question is whether habituation works the same way for any odorant or whether we habituate differently to each odorant? In particular, whether chemical, physical or perceptual cues can limit or increase habituation. To test this, the odour intensity of 32 odorants differing in physicochemical characteristics was rated by 58 participants continuously during 120s. Each odorant was delivered at a constant concentration. Results showed odorants differed significantly in habituation, highlighting the multifactoriality of habituation. Additionally habituation was predicted from 15 physico-chemical and perceptual characteristics of the odorants. The analysis highlighted the importance of trigeminality which is highly correlated to intensity and pleasantness. The vapour pressure, the molecular weight, the Odor Activity Value (OAV) and the number of double bonds mostly contributed to the modulation of habituation. Moreover, length of the carbon chain, number of conformers and hydrophobicity contributed to a lesser extent to the modulation of habituation. These results highlight new principles involved in the fundamental process of habituation, notably trigeminality and the physicochemical characteristics associated.

The Role of Odor-Evoked Memory in Psychological and Physiological Health

This article discusses the special features of odor-evoked memory and the current state-of-the-art in odor-evoked memory research to show how these unique experiences may be able to influence and benefit psychological and physiological health. A review of the literature leads to the conclusion that odors that evoke positive autobiographical memories have the potential to increase positive emotions, decrease negative mood states, disrupt cravings, and reduce physiological indices of stress, including systemic markers of inflammation. Olfactory perception factors and individual difference characteristics that would need to be considered in therapeutic applications of odor-evoked-memory are also discussed. This article illustrates how through the experimentally validated mechanisms of odor-associative learning and the privileged neuroanatomical relationship that exists between olfaction and the neural substrates of emotion, odors can be harnessed to induce emotional and physiological responses that can improve human health and wellbeing.

Olfactory Performance Can Be Influenced by the Presentation Order, Background Noise, and Positive Concurrent Feedback

Sniffin' Sticks have become a popular procedure to measure overall olfactory functionality with 3 subtest: phenyl ethyl alcohol threshold test (T), discrimination (D), and identification (I). However, several procedural components specified by the original paper have not been tested nor has the impact of deviations been measured. The aim of the present work was to measure olfactory performance under modified testing procedures. First, the reverse order of subtests (IDT) was compared with more standard practices (TDI). Next, the possible impact of background noise and positive concurrent feedback were assessed. A total of 120 individuals participated in the study where the 3 conditional experiments, each involving 40 participants, were completed. Testing procedures that reversed the presentation order of subtests (I->D->T) scored a significantly lower overall TDI score than standard testing order with the threshold subtest being the most influenced. Additionally, nonverbal background noise lowered overall olfactory performance while concurrent feedback modulated threshold performance. These results emphasize the importance of testing parameters where olfactory perception and tasks may be modulated by adaptation and attentional distraction, respectively. This study helped furthermore to demonstrate that the investigated 3 deviations from the standard procedure revealed a significant impact on the performance outcome in olfactory assessment using the Sniffin' Sticks.

Rivalry of homeostatic and sensory-evoked emotions: Dehydration attenuates olfactory disgust and its neural correlates

Neural correlates have been described for emotions evoked by states of homeostatic imbalance (e.g. thirst, hunger, and breathlessness) and for emotions induced by external sensory stimulation (such as fear and disgust). However, the neurobiological mechanisms of their interaction, when they are experienced simultaneously, are still unknown. We investigated the interaction on the neurobiological and the perceptional level using subjective ratings, serum parameters, and functional magnetic resonance imaging (fMRI) in a situation of emotional rivalry, when both a homeostatic and a sensory-evoked emotion were experienced at the same time. Twenty highly dehydrated male subjects rated a disgusting odor as significantly less repulsive when they were thirsty. On the neurobiological level, we found that this reduction in subjective disgust during thirst was accompanied by a significantly reduced neural activity in the insular cortex, a brain area known to be considerably involved in processing of disgust. Furthermore, during the experience of disgust in the satiated condition, we observed a significant functional connectivity between brain areas responding to the disgusting odor, which was absent during the stimulation in the thirsty condition. These results suggest interference of conflicting emotions: an acute homeostatic imbalance can attenuate the experience of another emotion evoked by the sensory perception of a potentially harmful external agent. This finding offers novel insights with regard to the behavioral relevance of biologically different types of emotions, indicating that some types of emotions are more imperative for behavior than others. As a general principle, this modulatory effect during the conflict of homeostatic and sensory-evoked emotions may function to safeguard survival.

Evaluation of the role of g protein-coupled receptor kinase 3 in desensitization of mouse odorant receptors in a Mammalian cell line and in olfactory sensory neurons

Thousands of odors are sensed and discriminated by G protein-coupled odorant receptors (ORs) expressed in olfactory sensory neurons (OSNs). G protein-coupled receptor kinases (GRKs) may have a role in desensitization of ORs. However, whether ORs are susceptible to agonist-dependent desensitization and whether GRKs affect odorant responsiveness of OSNs are currently unknown. Here we show that GRK3 attenuated the agonist responsiveness of a specific mouse odorant receptor for eugenol (mOR-EG) upon agonist pretreatment in HEK293 cells, but GRK3 did not affect the response amplitude or the recovery kinetics upon repeated agonist stimulation. We performed electrophysiological recordings of single OSNs which expressed mOR-EG and green fluorescent protein (GFP) in the presence or absence of GRK3. The kinetics and amplitude of agonist responsiveness of individual GFP-labeled mOR-EG neurons were not significantly affected by the absence of GRK3. These results indicate that the role of GRK3 in attenuating ORs responsiveness in OSNs may have been overestimated.